Splenic contraction and cardiovascular responses are augmented during apnea compared to rebreathing in humans.

The spleen contracts during apnea, releasing stored erythrocytes, thereby increasing systemic hemoglobin concentration (Hb). We compared apnea and rebreathing periods, of equal sub-maximal duration (mean 137 s; SD 30), in eighteen subjects to evaluate whether respiratory arrest or hypoxic and hypercapnic chemoreceptor stimulation is the primary elicitor of splenic contraction and cardiovascular responses during apnea. Spleen volume, Hb, cardiovascular variables, arterial (SaO), cerebral (ScO), and deltoid muscle oxygen saturations (SmO) were recorded during the trials and end-tidal partial pressure of oxygen (PO) and carbon dioxide (PCO) were measured before and after maneuvers.

Visualisation of individual dopants in a conjugated polymer: sub-nanometre 3D spatial distribution and correlation with electrical properties.

While molecular doping is ubiquitous in all branches of organic electronics, little is known about the spatial distribution of dopants, especially at molecular length scales. Moreover, a homogeneous distribution is often assumed when simulating transport properties of these materials, even though the distribution is expected to be inhomogeneous. In this study, electron tomography is used to determine the position of individual molybdenum dithiolene complexes and their three-dimensional distribution in a semiconducting polymer at the sub-nanometre scale.

Toughening of a Soft Polar Polythiophene through Copolymerization with Hard Urethane Segments.

Polar polythiophenes with oligoethylene glycol side chains are exceedingly soft materials. A low glass transition temperature and low degree of crystallinity prevents their use as a bulk material. The synthesis of a copolymer comprising 1) soft polythiophene blocks with tetraethylene glycol side chains, and 2) hard urethane segments is reported.

Ground-state electron transfer in all-polymer donor-acceptor heterojunctions.

Doping of organic semiconductors is crucial for the operation of organic (opto)electronic and electrochemical devices. Typically, this is achieved by adding heterogeneous dopant molecules to the polymer bulk, often resulting in poor stability and performance due to dopant sublimation or aggregation. In small-molecule donor-acceptor systems, charge transfer can yield high and stable electrical conductivities, an approach not yet explored in all-conjugated polymer systems.

Lignin-first biomass fractionation using a hybrid organosolv - Steam explosion pretreatment technology improves the saccharification and fermentability of spruce biomass.

For a transition to a sustainable society, fuels, chemicals, and materials should be produced from renewable resources. Lignocellulosic biomass constitutes an abundant and renewable feedstock; however, its successful application in a biorefinery requires efficient fractionation into its components; cellulose, hemicellulose and lignin. Here, we demonstrate that a newly established hybrid organosolv - steam explosion pretreatment can effectively fractionate spruce biomass to yield pretreated solids with high cellulose (72% w/w) and low lignin (delignification up to 79.

A novel hybrid organosolv: steam explosion method for the efficient fractionation and pretreatment of birch biomass.

Background: The main role of pretreatment is to reduce the natural biomass recalcitrance and thus enhance saccharification yield. A further prerequisite for efficient utilization of all biomass components is their efficient fractionation into well-defined process streams. Currently available pretreatment methods only partially fulfill these criteria.

Dark states in ionic oligothiophene bioprobes--evidence from fluorescence correlation spectroscopy and dynamic light scattering.

Luminescent conjugated polyelectrolytes (LCPs) can upon interaction with biological macromolecules change their luminescent properties, and thereby serve as conformation- and interaction-sensitive biomolecular probes. However, to exploit this in a more quantitative manner, there is a need to better understand the photophysical processes involved. We report studies of the conjugated pentameric oligothiophene derivative p-FTAA, which changes optical properties with different p-FTAA concentrations in aqueous buffers, and in a pH and oxygen saturation dependent manner.

Interactions between a luminescent conjugated oligoelectrolyte and insulin during early phases of amyloid formation.

Aggregates of misfolded proteins play an important role in diseases such as Alzheimer's. Here it is demonstrated how the anionic oligothiophene p-FTAA interacts with and influences pre-fibrillar protein assemblies during the earlier stages of in vitro fibrillation. Conjugated polythiophenes have previously been demonstrated to detect and discriminate between different types of protein aggregates and also introduce luminescent or conductive properties to these nanoscale fiber structures.

Fate of excitations in conjugated polymers: single-molecule spectroscopy reveals nonemissive "dark" regions in MEH-PPV individual chains.

Single chains of the conjugated polymer MEH-PPV (poly(2-methoxy-5-(2'-ethylhexyloxy)-1,4-phenylenevinylene)) were studied with wide-field fluorescence microscopy (dispersion in inert polymer matrices) and with fluorescence correlation spectroscopy (chloroform solution). The fluorescence yield of individual molecules in matrices was found to be 1-2 orders of magnitude lower than that in solution and it decreased substantially with increasing chain length. It suggests that isolation of MEH-PPV molecules in polymer matrices creates favorable conditions for photogeneration of nonemissive primary excited states.

Modulation filtering enables removal of spikes in fluorescence correlation spectroscopy measurements without affecting the temporal information.

The appearance of intensity spikes in measurements is a common problem in fluorescence correlation spectroscopy (FCS) studies of biological samples. In this work, we present a new method for generating artifact-free correlation curves from fluorescence traces that have undergone spike removal. This method preserves the temporal information throughout the measurement and properly represents the correlation between events separated by removed spikes.

Fluorescence cross-correlation spectroscopy of a pH-sensitive ratiometric dye for molecular proton exchange studies.

Fluorescence fluctuation analysis of individual pH-sensitive fluorophores has recently proven to be a useful approach for biomolecular proton exchange studies. In this work, dual-color fluorescence cross-correlation spectroscopy (FCCS) is demonstrated on a ratiometric pH-sensitive dye, for which both the excitation and emission spectra shift as a function of pH. In the FCCS measurements, the fluorescence signal from the predominant emission wavelength range of the protonated form of the dye is cross-correlated with that of the deprotonated form.

Transient state imaging for microenvironmental monitoring by laser scanning microscopy.

Photoinduced transient dark states are exhibited by practically all common fluorophores. These relatively long-lived states are very sensitive to the local environment and thus highly attractive for microenvironmental imaging purposes. However, because of methodological constraints, their sensitivity has to date been very sparsely exploited.

Modulated fluorescence correlation spectroscopy with complete time range information.

Two methods to combine fluorescence correlation spectroscopy (FCS) with modulated excitation, in a way that allows extraction of correlation data for all correlation times have been developed and experimentally verified. One method extracts distortion-free correlation data from measurements acquired with standard hardware correlators provided the fluorescence does not change systematically within the excitation pulses. This restriction does not apply to the second method, which, however, requires time-resolved acquisition of the fluorescence intensity.

Monitoring kinetics of highly environment sensitive states of fluorescent molecules by modulated excitation and time-averaged fluorescence intensity recording.

In this work, a concept is described for how the kinetics of photoinduced, transient, long-lived, nonfluorescent or weakly fluorescent states of fluorophore marker molecules can be extracted from the time-averaged fluorescence by using time-modulated excitation. The concept exploits the characteristic variation of the population of these states with the modulation parameters of the excitation and thereby circumvents the need for time resolution in the fluorescence detection. It combines the single-molecule sensitivity of fluorescence detection with the remarkable environmental responsiveness obtainable from long-lived transient states, yet does not in itself impose any constraints on the concentration or the fluorescence brightness of the sample molecules that can be measured.