A New Method to Record Subglottal Pressure Waves: Potential Applications

Rapid subglottal pressure changes related to the glottal cycles influence the aerodynamics of phonation. Various methods to measure these have been developed, but are not practical for routine phoniatric use. For that reason, a noninvasive measurement tool is necessary. This article presents a technique that uses a microphone positioned at the skin of the jugular fossa to record the signal which arises in the subglottal spaces and is transmitted through the soft tissue to the surface of the skin. Using the program Glottal Segmentation of Voice and Speech, jugular microphone recordings from two healthy subjects were compared with simultaneously recorded direct intratracheal measurements during the same phonation. A systematic error arising from the transmission properties of the microphone and the soft tissue leads to phase and amplitude deviations. These must be taken into account and require correction. This correction procedure leads to high correlations and a good agreement between the two signals. Even without this correction the jugular microphone measurements proved to be useful as a diagnostic and a therapeutic tool in cases where chest resonance specific processes appear affected. In addition, they offer material for research purposes. Although based on a small number of subjects, the new method shows a good validity; testing on a larger number of subjects will probably strengthen the validity.     

Poly(ethyleneimine)‐Mediated Large‐Scale Transient Gene Expression: Influence of Molecular Weight,Polydispersity and N‐Propionyl Groups

Three synthesis lots of linear poly(ethyleneimine) (PEI) are compared to a fully hydrolyzed linear PEI (commercially available as PEI “Max”) regarding structure, polyplex formation with plasmid DNA, and transfection of suspension‐adapted HEK‐293E cells. PEI “Max” binds DNA more efficiently than the other PEIs, but it is the least effective in terms of transient recombinant protein yield. One PEI lot is fractionated by means of SEC. The fractions of high‐$\overline {M} _{{\rm n}} $ PEI are the most efficient for complex formation and transfection. Nevertheless, the highest transient recombinant protein yields are achieved with unfractionated PEI. The results demonstrate that the polydispersity and charge density of linear PEI are important parameters for gene delivery to suspension‐adapted HEK‐293E cells.

     

Cell Uptake and Trafficking Behavior of Non‐covalent,Coiled‐coil Based Polymer–Drug Conjugates

This paper reports on the cell uptake and trafficking properties of a series of non‐covalent polymer–drug conjugates. These nanomedicines are composed of a poly(N‐(2‐hydroxypropyl)methacrylamide) backbone functionalized with multiple copies of a drug. The drug moieties are attached to the polymer via a non‐covalent, so called coiled coil motif, which is formed by heterodimerization of two complementary peptide strands, one of which is attached to the polymer carrier and the other to the drug. Cytotoxicity and FACS experiments, which were carried out with model anticancer drug or fluorophore conjugates, provided insight into the cell uptake and trafficking behavior of these conjugates.

     

Symmetric and quasi-symmetric functions associated to polymatroids

To every subspace arrangement X we will associate symmetric functions ℘[X] and ℋ[X]. These symmetric functions encode the Hilbert series and the minimal projective resolution of the product ideal associated to the subspace arrangement. They can be defined for discrete polymatroids as well. The invariant ℋ[X] specializes to the Tutte polynomial . Billera, Jia and Reiner recently introduced a quasi-symmetric function ℱ[X] (for matroids) which behaves valuatively with respect to matroid base polytope decompositions. We will define a quasi-symmetric function for polymatroids which has this property as well. Moreover, specializes to ℘[X], ℋ[X], and ℱ[X]. The author is partially supported by the NSF, grant DMS 0349019.     

Reversible gelation of poly(dimethylsiloxane) with ionic and hydrogen‐bonding substituents

Poly(dimethylsiloxane) copolymers containing a small fraction of carboxylic acid or Zn‐carboxylate groups were prepared and compared regarding reversible gelation by hydrogen‐bonding and ion‐pair interaction. The polymers were synthesized by condensation of a t‐butylcarboxylate functionalized dichlorosilane with an α,ω‐dihydroxy‐poly(dimethylsiloxane), followed by thermal cleavage of the ester bond. Neutralization of the resulting carboxylic acid substituents was achieved by addition of Zn (acac)₂. Reversible crosslinking was investigated by step stress and oscillating shear experiments. The carboxylic acid containing poly(dimethylsiloxane) became rubberlike upon increasing the temperature and liquified again when it was brought back to room temperature. This observation has been explained tentatively by segregation of the carboxylic acid groups into polar domains at high temperatures [i.e., a behavior like it is observed for systems with a lower critical solution temperature (LCST)]. At ambient temperature, the carboxylic acid groups undergo hydrogen bonding to the Si–O–Si backbone. Clustering of the carboxylic acid groups occurs only as these hydrogen bonds break upon raising temperature. Moisture was found to have a strong influence on the reversal of the crosslinking. Addition of zinc acetylacetonate resulted in the formation of an elastic network already at ambient conditions consistent with the concept of ionomers which undergo reversible gelation by formation of ion‐pair multiplets and clusters in the hydrophobic polymer matrix in particularly at low temperatures. At high temperature, both the carboxylic acid and the carboxylate sample exhibited a rather similar viscoelastic behavior consistent with a common structure where transient crosslinks are formed by clusters of the carboxylic acid and the carboxylate groups. © 1999 John Wiley & Sons, Inc. J Polym Sci B: Polym Phys 37: 485–495, 1999     

Microphase separation and rheology of a semicrystalline poly(ether-ester) multiblock copolymer

A microphase separation transition (MST) of a thermoplastic elastomer based on soft segments of poly(tetra methylene oxide) and hard crystalline segments of poly(tetra methylene terephthalate) has been studied by means of rheological measurements, differential scanning calorimetry (DSC), and wide-angle X-ray scattering (WAXS), showing that the MST is entirely caused by melting/crystallization, and that no separate segmental mixing/demixing transition is involved. DSC and WAXS measurements show that melting starts at 190°C, leading to crystal reorganization effects up to above 200°C, and that a gradual decrease in crystallinity occurs from below 210°C up to 224°C, above which temperature no crystals are left. Rheological measurements reveal a wide MST (207–224°C) upon heating, which coincides perfectly with the melting range. From this coincidence together with the Maxwell fluid behavior directly following the MST, it is concluded that melting leads to a one-phase liquid, and that no separate segmental mixing transition occurs. Similar results are obtained upon cooling, indicating that crystallization is the driving force for phase separation and that no separate segmental demixing step precedes crystallization. The wide MST implies a large processing window over which the rheological properties change from highly elastic, with a distinct yield stress, to normal pseudoplastic, enabling application in preparation of structured blends. © 1998 John Wiley & Sons, Inc. J Polym Sci B: Polym Phys 36: 1795–1804, 1998     

Novel protective coatings for steel based on a combination of self-assembled monolayers and conducting polymers

Investigations for a new primer system for iron or low alloyed steel have led to first results. Several special phosphonic acids with thiophene derivatives as head groups have been synthesized. They form stable self-assembled monolayers (SAMs) on passivated iron by dipping the substrates into aqueous phosphonic acid solutions. SAM formation was validated by current potential curves and also by contact angle measurements, which showed an intensive hydrophobisation of the iron surface after the dipping process. Finally cyclovoltammetric (CV) experiments after SAM formation indicated the successful polymerisation of the immobilised thiophene derivatives.