Influence of staff number and internal constellation on surgical site infection in an operating room

Prediction of bacteria-carrying particle （BCP） dispersion and particle distribution released from staffmem- bers in an operating room （OR） is very important for creating and sustaining a safe indoor environment. Postoperative wound infections cause significant morbidity and mortality, and contribute to increased hospitalization time. Increasing the number of personnel within the OR disrupts the ventilation airflow pattern and causes enhanced contamination risk in the area of an open wound. Whether the amount of staffwithin the OR influences the BCP distribution in the surgical zone has rarely been investigated. This study was conducted to explore the influence of the number of personnel in the OR on the airflow field and the BCP distribution. This was performed by applying a numerical calculation to map the airflow field and Lagrangian particle tracking （LPT） for the BCP phase. The results are reported both for active sampling and passive monitoring approaches. Not surprisingly, a growing trend in the BCP concentration （cfu/ms） was observed as the amount of staff in the OR increased. Passive sampling shows unpredictable results due to the sedimentation rate, especially for small particles （5-10 i~m）. Risk factors for surgical site infections （SSls） must be well understood to develop more effective prevention programs.     

Clean and reactive nanostructured cellulose surface

A simple, solvent-free and low cost method to activate the surface of nanofibrillated cellulose films for further functionalization is presented. The method is based on the oxidative properties of UV radiation and ozone, to effectively remove contaminants from nanocellulosic surface, which remains clean and reactive for at least a week. The efficiency of the method is demonstrated by X-ray photoelectron spectroscopy (XPS) and contact angle measurements. In clear contrast to previous results on nanoscaled cellulose the relative atomic concentration of non-cellulosic carbon atoms was only 4 %, and water completely wetted the surface within seconds. After activation, neither chemical degradation nor morphological changes on cellulose were observed. This surface activation is essential for further functionalization of the film in dry state or nonpolar media. The surface activation was confirmed by silylation and a four times higher degree of substitution was achieved on the activated sample compared to non-activated reference film, as monitored with XPS.     

Quantitative assessment of the enzymatic degradation of amorphous cellulose by using a quartz crystal microbalance with dissipation monitoring

The systematic evaluation of the degradation of an amorphous cellulose film by a monocomponent endoglucanase (EG I) by using a quartz crystal microbalance with dissipation monitoring (QCM-D) identified several important aspects relevant to the study the kinetics of cellulose degradation by enzymes. It was demonstrated that, to properly evaluate the mechanism of action, steady state conditions in the experimental set up need to be reached. Rinsing or diluting the enzyme, as well as concentration of the enzyme, can have a pronounced effect on the hydrolysis. Quantification of the actual hydrolysis was carried out by measuring the film thickness reduction by atomic force microscopy after the enzymatic treatment. The values correlated well with the frequency data obtained by QCM-D measurement for corresponding films. This demonstrated that the evaluation of hydrolysis by QCM-D can be done quantitatively. Tuning of the initial thickness of films enabled variation of the volume of substrate available for hydrolysis which was then utilized in establishing a correlation between substrate volume and hydrolytic activity of EG I as measured by QCM-D. It was shown that, although the amount of substrate affects the absolute rate of hydrolysis, the relative rate of hydrolysis does not depend on the initial amount of substrate in steady state system. With this experimental setup it was also possible to demonstrate the impact of concentration on crowding of enzyme and subsequent hydrolysis efficiency. This effort also shows the action of EG I on a fully amorphous substrate as observed by QCM-D. The enzyme was shown to work uniformly within the whole volume of swollen film, however being unable to fully degrade the amorphous film.     

Preparation of Langmuir/Blodgett-cellulose Surfaces by Using Horizontal Dipping Procedure. Application for Polyelectrolyte Adsorption Studies Performed with QCM-D

A method of preparing model cellulose surfaces by the Langmuir–Blodgett (LB) technique with horizontal dipping procedure has been developed. The primary aim for the use of these surfaces was adsorption studies performed with the quartz crystal microbalance with dissipation (QCM-D) instrument. Hydrophobised cellulose (trimethylsilyl cellulose, TMSC) was deposited on the hydrophobic, polystyrene-coated QCM-D crystal. After 15 dipping cycles, the TMSC film fully covers the crystal surface. TMSC can easily be hydrolysed back to cellulose with acid hydrolysis. With this method a smooth, rigid, thin and reproducible cellulose film was obtained. Its morphology, coverage, chemical composition and wetting was further characterised using atomic force microscopy (AFM), X-Ray photoelectron spectroscopy (XPS), and contact angle measurements. The swelling behaviour and the stability of the cellulose film in aqueous solutions at different ionic strengths were studied using the QCM-D instrument. The swelling/deswelling properties of the cellulose film were those expected of polyelectrolytes with low charge density; some swelling occurred in pure water and the swelling decreased when the ionic strength was increased. No significant layer softening was detected during the swelling. The effect of electrolyte concentration and polymer charge density on the adsorption of cationic polyelectrolytes on the cellulose surface was also investigated. At low electrolyte concentration less of the highly charged PDADMAC was adsorbed as compared to low charged C-PAM. The adsorbed amount of PDADMAC increased with increasing ionic strength and a more compact layer was formed while the effect of electrolyte concentration on the adsorption of C-PAM was not as pronounced.     

Study of the lithiated phenylacetonitrile monoanions and dianions formed according to the lithiated base used (LHMDS,LDA, or n-BuLi). 1. Evidence of heterodimer ("Quadac") or dianion formation by vibrational spectroscopy

It is evidenced through vibrational spectroscopy that a heterodimer or "Quadac" is formed when an excess of base (LHMDS, LDA, or n-BuLi) is added to PhCH(2)CN in THF, THF-hexane, or THF-toluene solution. The amount of heterodimer increases with the pK(H)(a) of the lithiated base. A dianionic species may be formed through decomposition of this heterodimer if the pK(H)(a) of the base is sufficiently high, as in the case of n-BuLi. With LDA, only a very small amount of dianion is observed, and with LHMDS, no dianion is detected. The predominant dianionic species observed are the linear and bridged separated ion pairs of the dilithiated dianion. The presence of the amine in the medium is of paramount importance. The PhCHCNLi monomer-dimer equilibrium is entropy driven toward the dimer solvated by the amine.     

Characterization of the interaction of hypericin with protein kinase C in U-87 MG human glioma cells

A fluorescence imaging technique was used to monitor intracellular localization of protein kinase C (PKC) in U-87 MG human glioma cells in the presence of hypericin (Hyp) and phorbol 12-myristate-13-acetate (PMA). It is shown that PKC localization, which reflects its activity, is influenced by Hyp and this influence is different from that observed for PMA which acts as PKC activator. Fluorescence binding experiments were used to determine the binding constants of Hyp to several isoforms of PKC. The obtained values of K(d)s (approximately 100 nM) suggest that Hyp binds with high affinity to PKC. Finally, molecular modeling was used to compare structural models of the interaction of C1B domain of PKC (PKC isoforms alpha, delta, gamma) with Hyp and our previously published model of the (C1B domain PKCgamma)/PMA complex. The influence of Hyp on PKC translocation in U-87 MG cells in comparison with PMA, colocalization fluorescence pattern of Hyp and PKC, the higher binding affinity of Hyp to PKC in comparison with known binding constants of phorbol esters, as well as the binding mode of Hyp and PMA to the C1B domain of PKC suggested by molecular modeling, support the idea that Hyp and PMA might competitively bind to the regulatory domain of PKC.     

Adsorption of complexes formed by cationic starch and anionic surfactants on quartz studied by QCM-D

The adsorption of complexes of cationic starch, (CS) and a series of homologous sodium alkanoates on silica was studied with the quartz crystal microbalance with dissipation (QCM-D) instrument. The systems were chosen so as to represent CS/surfactant ratios below and above the critical association concentrations of the surfactants but below their critical micelle concentrations. It was found that

– surfactants did not adsorb on cationic polymers that were very tightly bound to the surface;

– surfactants did adsorb on polyelectrolytes forming layers with loops and tails extending into the solution, provided the concentration of surfactant was at least around the critical association concentration (cac) of the surfactant/polymer system;

– adsorption of surfactant was promoted by increasing the surfactant chain length and by adding simple electrolyte that weakened the electrostatic polymer/surface interaction and

– multilayers were formed when the surfactant concentration in solution was well above the cac; their formation was promoted by increasing hydrophobic interactions, e.g. by increasing the surfactant chain length.

Viscoelastic properties of cationic starch adsorbed on quartz studied by QCM-D

The adsorption and viscoelastic properties of layers of a cationic polyelectrolyte (cationic starch, CS, with 2-hydroxy-3-trimethylammoniumchloride as the substituent) adsorbed from aqueous solutions (pH 7.5, added NaCl 0, 1, 100, and 500 mM) on silica were studied with a quartz crystal microbalance with dissipation (QCM-D). Three different starches were investigated (weight-average molecular weights M(w) approximately 8.7 x 10(5) and 4.5 x 10(5) with degree of substitution DS = 0.75 and M(w) approximately 8.8 x 10(5) with DS = 0.2). At low ionic strength, the adsorbed layers are thin and rigid and the amount adsorbed can be calculated using the Sauerbrey equation. When the ionic strength is increased, significant changes take place in the amount of adsorbed CS and the viscoelasticity of the adsorbed layer. These changes were analyzed assuming that the layer can be described as a Voigt element on a rigid surface in contact with purely viscous solvent. It was found that CS with low charge density forms a thicker and more mobile layer with higher viscosity and elasticity than CS with high charge density. The polymers adsorbed on the silica even when the ionic strength was so high that electrostatic interactions were effectively screened. At this high ionic strength, it was possible to study the effect of molecular weight and molecular weight distribution of the CS on the properties of the adsorbed film. Increasing the molecular weight of CS resulted in a larger hydrodynamic thickness. CS with a narrow molecular weight distribution formed a more compact and rigid layer than broadly distributed CS, presumably due to the better packing of the molecules.     

Structural studies of carbanionic species α to a phosphoryl group; anion from ketophosphonate comparison with related enoxysilanes and p-ylid

The structure of the carbanionic species 4 formed from diethyl(2-oxopropyl)phosphonate and t-BuOK has been studied by ¹H, ¹³C and ³¹P NMR. In an associating medium (pyridine), a single chelated (C) carbanionic species 4Z (C) is observed. Two slowly interconverting species 4Z and 4E co-exist when the anion-cation interaction is loose, i.e. in Me₂SO and when the gegenion K⁺ is complexed to (2,2,2)cryptand in Me₂SO. The anionic carbon of 4Z and 4E is planar, and they have a strong enolate character as shown by the barrier to rotation around the C-1? C-2 bond (ΔG_c?～92 KJ mol^?1). Their structures are compared to those of the related E and Z 1-diethylphosphonato-2-trimethylsilyloxypropenes and to (acetylmethylene)triphenylphosphorane.     

Sensitivity analysis in lightning protection risk management

The total risk R can be expressed by the following equation: R = NPL, where N is the number of dangerous events, P is the probability of damage and L measures the amount of loss. These parameters can be regarded as macroparameters in the sense that they can be given as a function of additional parameters (microparameters).Methods of calculation, check and refinement of parameter values have always been general themes of the standardization. The comparison of standards IEC 62305-2:2006 Ed. 1 and IEC 62305-2:2010 Ed. 2 is a good example of these efforts, as changes underwent in the determination of the collection area of service and the value of some parameters, moreover new parameters were introduced in order to break existent parameters into more components.Though the international standard contains the value of parameters, it does not give any information about the procedure how these values were determined, nor about the theoretical considerations behind. Therefore it is proper to ask whether the changes of a given parameter value or introduction of a new parameter make radical changes in resulting risk value or not.In this study sensitivity analysis was used to investigate how the individual macro- and micro parameters influence the risk. Moreover it was determined whether or not new parameters and calculations have an effect on the importance of the respective components of the resulting risk.The sensitivity analysis was done for two case studies in the standard, a country house and an office building respectively, with both editions of the standard.