Silicone/vegetable oil Janus emulsion: topological stability versus interfacial tensions and relative oil volumes.

Several aspects were studied of the formation and destabilization in bulk of silicone/vegetable oil, SO/VO, Janus emulsions, stabilized by Tween 80. In the formation of the emulsions, it was unexpectedly found that the dispersions tended to contain both single and flocculated drops irrespective of the emulsification intensity. Microscopy of the emulsions with no cover glass revealed flocculated drops of a large (200-500 µm) central SO drop with many small VO drops attached. Applying a cover glass did not significantly change the drop size; instead two-oil Janus drops of well-defined contact angle were found. The emulsions showed rapid creaming irrespective of the preparation method, but a few days storage did not significantly change the drop size in the creamed layer, nor was separation of the oils detected. The total interfacial free energy of the Janus drops at equilibrium was compared to the two relevant alternatives; engulfed and separate drops. The Janus drop free energies were found less for all volume ratios of the oils, when the surfactant concentrations in the aqueous phase was sufficient to prevent spreading of VO on SO. Changing the surfactant concentration to bring the interfacial tensions closer to the critical value for spreading gave declining interfacial free energy difference to that of engulfed drops.

Selective emulsion inversion in an equilibrium Janus drop. 1. Unlimited space.

The potential for a catastrophic inversion of one phase in a Janus emulsion drop was investigated by local equilibrium calculations of a single Janus drop of two mutually insoluble oils, O1 and O2, in an infinite aqueous continuous phase, (O1+O2)/W. The relative volume of the oil with less interfacial tension towards water, O2, was increased, while the radius of the O1 part of the drop was held constant at unity. The limiting fraction of O1 covered by O2 was calculated for infinite O2 volume for a selected interfacial tension combination. After the O2 volume reached infinity, the volume of the continuous aqueous phase was reduced to finite values, leading to a selective inversion of the emulsion from (O1+O2)/W to (W+O1)/O2. Thenceforward, further removal of the water led to an additional reduction of the size and radius of the water cap.

Assessment of horizontal laminar air flow instrument table for additional ultraclean space during surgery.

The area in a vertical ultraclean laminar air flow (LAF) theatre is usually too small to accommodate all the equipment needed for major surgery. We investigated the addition of an instrument table supplied with fixed ultraclean LAF and placed alongside the existing main LAF unit, to determine its physical and bacteriological effect on the main unit. In phase 1, with two investigators but without a patient, smoke tests showed no intrusion of air from the table into the main unit and particle counts did not show any adverse effect on the main LAF unit. In phase 2, during patients undergoing two total knee replacements, the LAF table and a table without LAF were placed alongside the main LAF unit. The tables were subjected to the activity of an extra operating room (OR) nurse working from inside the main LAF vigorously simulating handling of instruments. During this activity, the >5µm particle counts were 275/m(3) at the instrument table with LAF and 8550/m(3) at the table without LAF (P<0.0001). Also, without the OR nurse activity, the particle counts, just inside the main unit and adjacent to the LAF table, were significantly reduced (P<0.03-0.003). Sedimentation plates on the LAF table and in the main unit registered 22 and 25cfu/m(2)/h respectively compared with 45cfu/m(2)/h at the instrument table without LAF. In conclusion, the results from the smoke tests, particle counts and bacteriological evaluation showed that the additional instrument table supplied with LAF is efficient and can be safely used as an extension additional to a main OR LAF unit.

OECI Workshop on late side-effects of cancer treatments.

This Workshop was organised by the Organisation of European Cancer Institutes (OECI) to provide a forum for discussing the late side-effects resulting from different cancer treatments. One of the main Workshop objectives was to generate recommendations on how to improve knowledge and, consequently, long-term care for cancer survivors.

Aerobiology in the operating room and its implications for working standards.

Two novel operating room (OR) ventilation concepts, i.e. the upward displacement or thermal convection system and the exponential ultra-clean laminar air flow (LAF) designed to function without extra walls, were evaluated from a bacteriological point of view. The thermal convection system (17 air changes/h) was compared with conventional ventilation (16 air changes/h) with an air inlet at the ceiling and evacuation at floor level. The exponential LAF was compared with the vertical ultra-clean LAF and the horizontal ultra-clean LAF, both with extra side walls. The comparison was made using strictly standardized simulated operations and, except for the horizontal LAF, it was performed in the same OR where the type of ventilation was changed. In the different areas important for surgical asepsis, the thermal system resulted in a twofold to threefold increase in bacterial air and surface counts compared to the conventional system (statistical significance = p < 0.05-0.0001). The bacteriological efficiency of the exponential LAF was equal to the horizontal and vertical LAF units with extra walls in the OR, and all three systems easily fulfilled the criteria for ultra-clean air, i.e. bacteria-carrying particles < 10/m3. In the areas important for surgical asepsis the turbulent ventilation systems yielded highly significant correlation between air and surface contamination (p < 0.02-0.0006). No such correlation existed in the LAF systems.

Evaporation of a model skin lotion with beta-hydroxy acids.

Two beta-hydroxy acids, malic and salicylic acids were combined with a non-ionic surfactant, a commercial pentaoxyethylene sorbitan mono-oleate and water to form a simple model of a skin lotion and the phase diagrams were determined. One emulsion formulation with relative amounts of the three components similar to those in commercial lotions was used to observe microscopically the changes in the emulsion structure during evaporation. The microscope images were subsequently compared to the information from the phase diagram under equilibrium conditions. The results showed the behavior of the systems of the two acids to be distinctly different; as exemplified by that of a typical formulation with 3% by weight of acid and 5% of surfactant. The malic acid system consisted of vesicles, exclusively formed by the surfactant and water, in an aqueous molecular solution of the acid and the initial evaporation resulted in an increase of the acid concentration in the aqueous solution to reach 35.5%, before solid crystals of the acid solid solution appeared. The salicylic acid formulation, on the other hand, already at the beginning of the determination consisted of water, particles of the acid solid solution and surfactant vesicles. In both cases the remaining deposit after total evaporation was particles of a solid acid solution and liquid surfactant.

Amphiphilic association structures in a model skin lotion with hydroxy acids.

The phase diagrams were determined of lactic and isohexanoic hydroxy acids as well as salicylic acid with water, a non-ionic surfactant and a paraffinic oil to outline the influence of the hydroxy acids on the structure in a model for a skin lotion. The results showed the influence of the acid to be similar to that of the oil, but that the difference in chain length between the two alpha acids had only insignificant influence. The results are discussed from two aspects: the structures involved in the lotion as applied and the action of the lotion residue on the skin after the evaporation of the water.

The addition of a mobile ultra-clean exponential laminar airflow screen to conventional operating room ventilation reduces bacterial contamination to operating box levels.

A mobile screen producing ultra-clean exponential laminar airflow (LAF) was investigated as an addition to conventional turbulent/mixing operating room (OR) ventilation (16 air changes/h). The evaluation was performed in a small OR (50 m(3)) during 60 standardized operations for groin hernia including mesh implantation. The additional ventilation was used in 50 of the operations. The LAF passed from the foot-end of the OR table over the instrument and surgical area. Strict hygiene OR procedures including tightly woven and non-woven OR clothing were used. Sedimentation rates were recorded at the level of the patients' chests (N=60) (i.e. the air had passed the surgical team) and in the periphery of the OR. In addition bacterial air contamination was studied above the patients' chests in all 10 operations without the additional LAF and in 12 with the LAF. The screen reduced the mean counts of sedimenting bacteria (cfu/m(2)/h) on the patients' chests from 775 without the screen to 355 (P=0.0003). The screen also reduced the mean air counts of bacteria (cfu/m(3)) above the patients' chests from 27 to 9 (P=0.0001). No significant differences in mean sedimentation rates (cfu/m(2)/h) existed in the periphery of the OR where 628 without and 574 with screen were recorded. During the follow-up period of six months no surgical site infections were detected. In conclusion when the mobile LAF screen was added to conventional OR ventilation the counts of aerobic airborne and sedimenting bacteria-carrying particles downstream of the surgical team were reduced to the levels achieved with complete ultra-clean LAF OR ventilation (operating box).

Mobile zoned/exponential LAF screen: a new concept in ultra-clean air technology for additional operating room ventilation.

A mobile screen (0.5 x 0.4 m) producing ultra-clean exponential LAF (air-flow central zone 0.6 m/s and peripheral zone 0.4 m/s) was investigated as an addition to conventional turbulent/mixing operating room ventilation. The evaluation was performed during strictly standardized sham operations reflecting conditions during major surgery. The study consisted of a pilot experiment designed to give high counts of sedimenting aerobic colony forming units (cfu). In a second main study, recording dust particles, air-borne and sedimenting aerobic cfu, the screen was associated with optimal operating room clothing. In the pilot experiment the use of the screen resulted in a substantial reduction of sedimenting bacteria from 3835-4940 to 0-390 cfu/m(2)/h. In the main study, the use of the additional LAF reduced the surface contamination from 416-329 to 7-78 cfu/m(2)/h up to 1.6 m from the screen (P=0.001-0.0001). Measured in the wound area the screen reduced the air counts of bacteria from 9-14 to 0.2-0.4 cfu/m(3) (P=0.008-0.0001) and a marked reduction of air-borne dust particles was recorded (P=0.007-0.009). In conclusion, the additional mobile LAF screen reduced the counts of aerobic air-borne and sedimenting bacteria-carrying particles as well as dust particles to the levels gained with complete ultra-clean LAF room ventilation. Thus, the screen might prove a valuable addition to operating room ventilation as well as in other areas where asepsis is essential.

Nerve growth factor increases airway responses and decreases levels of exhaled nitric oxide during histamine challenge in an in vivo guinea-pig model.

There is a growing body of evidence supporting the idea that nerve growth factor (NGF) may be involved in the development of asthma-associated symptoms, such as airway hyper-responsiveness. Increased levels of NGF have recently been described in serum and in the airways of asthmatics. We have examined whether exhaled nitric oxide (NO) levels might be altered during the increased airway responses upon NGF treatment in guinea-pigs in vivo. Intravenous (i.v.) administration of histamine normally elicits a rapid peak in insufflation pressure (IP) and in exhaled NO, followed by a period of decreased concentrations of exhaled NO. Anaesthetized guinea-pigs were pre-treated intravenously with either saline, 4 or 80 ng x kg(-1) NGF 30 min before i.v. challenge with 16 microg x kg(-1) histamine. At 80 ng x kg(-1) NGF significantly enhanced the airway obstruction caused by histamine, whereas the peak acute increase in exhaled NO was not enhanced. Following the increase, came a rapid drop, an effect enforced in the NGF treated animals. Subsequently, the time to return to 90% of resting exhaled NO was increased, from 12 min in saline-treated animals to 48 min in NGF-treated animals. Our data confirm that NGF can enhance airway responses to histamine. Moreover, our study shows a decrease in exhaled NO following a histamine challenge, an effect enhanced by NGF. A reduced ability to release exhaled NO may be a mechanism for increased airway responses during elevated NGF levels. The interaction between NGF and airway NO formation, and its relation to airway responses, merit further investigation.

Poly(N-vinyl-2-pyrrolidone) and 1-Octyl-2-pyrrolidinone Modified Ionic Microemulsions.

The influence of the nonionic polymer poly(N-vinyl-2-pyrrolidone) (PVP) in comparison to the surfactant 1-octyl-2-pyrrolidinone (OP) on the phase behavior of the system SDS/pentanol/xylene/water was studied. In both modified systems a strong increase in the water solubilization capacity was found, accompanied by a change in the spontaneous curvature toward zero. In the polymer-modified system an isotropic phase channel is formed with increasing polymer content that connects the L1 and the L2 phase. The lamellar liquid crystalline phase is destabilized in both cases. In the L1 phase the adsorption of PVP at the surface of the microemulsion droplets and the formation of a cluster-like structure is proven by several methods like (13)C NMR T(1) relaxation time measurments, zeta potential measurements, and rheology. In the L2 phase a modification of the interface of the inverse droplets is detected by a shift in the percolation boundary (conductivity) and (13)C NMR T(1) relaxation measurements. The formation of a cluster-like structure can be assumed on the basis of our rheological measurements. Copyright 2001 Academic Press.

Surgical area contamination--comparable bacterial counts using disposable head and mask and helmet aspirator system, but dramatic increase upon omission of head-gear: an experimental study in horizontal laminar air-flow.

The effect of different head coverings on air-borne transmission of bacteria and particles in the surgical area was studied during 30 strictly standardized sham operations performed in a horizontal laminar air flow (LAF) unit. The operating team members wore disposable gowns plus either a non-sterile head covering consisting of a squire type disposable hood and triple laminar face mask, a sterilized helmet aspirator system or no head cover at all. In the wound area both types of head cover resulted in low and comparable air (means of 8 and 4cfu/m(3)) and surface contamination (means of 69 and 126cfu/m(2)/h) rates. Omission of head-gear resulted in a three- to five-fold increase (P > or = 0.01- 0.001), depending on site sampled air contamination rate (mean of 22cfu/m(3)) whereas the bacterial sedimentation rate in the wound area increased about 60-fold ( P > or = 0.0001). A proper head cover minimized the emission of apparently heavy particles that were not removed by the horizontal LAF and contained mainly streptococci, presumably of respiratory tract origin. Dust particle counts revealed no differences between the three experimental situations. No correlation between air and surface contamination rates or between air contamination and air particle counts was found. We conclude that, from a bacteriological point of view, disposable hoods of squire type and face masks are equally as efficient as a helmet aspirator system and both will efficiently contain the substantial emission of bacteria-carrying droplets from the respiratory tract occurring when head cover is omitted. Finally, the use of bacterial air counts to assess surgical site surface contamination in horizontal LAF units must be seriously questioned.

Phase diagram and emulsion stability of surfactant-fragrance systems.

Emulsions containing 95 wt.% water were prepared of a fragrance oil (limonene, the mixture of limonene and phenethyl alcohol in different ratios, and benzaldehyde), using a commercial tetraethyleneglycol lauryl ether (Laureth 4) as the stabilizer. The emulsion stability was observed both visually and with the aid of a microscope. The variation of emulsion stability with the fragrance/surfactant ratio is related to the phase changes in the system.

Change of amphiphilic association structures during evaporation from emulsions in surfactant-fragrance-water systems.

The phase diagrams of a nonionic surfactant (Laureth 4), water, and three different fragrance compounds, limonene, phenethyl alcohol and benzaldehyde, were compared. The location of the fragrance molecules in the lamellar liquid crystals (LLC) was investigated using the small-angle X-ray diffraction. The evaporation processes of the fragrance emulsions, consisting of 80 wt.% water, 15 wt.% fragrance and 5 wt.% surfactant, were followed both experimentally through an optical microscope, and theoretically through calculation based on the knowledge of the vapour pressure of the fragrance along the demixing line of the water-in-oil microemulsion (L(2)) phase boundary. Evaporation of the phenethyl alcohol emulsion led the system directly into the L(2) phase region, with very little phenethyl alcohol evaporated in 20 min. For the limonene system, during evaporation the system experienced several multi-phase regions, then reached the water-surfactant axis, and finally went into the L(2) phase region. By contrast to phenethyl alcohol, limonene evaporated completely within 10 min. Benzaldehyde emulsion went through structural changes similar to those of limonene, while the fragrance evaporated continuously until completion in 20 min.

Inconsistent correlation between aerobic bacterial surface and air counts in operating rooms with ultra clean laminar air flows: proposal of a new bacteriological standard for surface contamination.

The relationship between surface contamination (cfus/m2/h) with particles carrying aerobic bacteria and corresponding air contamination rates (cfus/m3) was evaluated in operating rooms (OR) equipped with ultra clean vertical or horizontal laminar airflow (LAF). For the evaluation we collected data during strictly standardized sham operations using non-woven disposable or cotton clothing. Air contamination in the wound and instrument areas (Casella slit sampler) was related to the surface contamination rate (settle plates) in the same areas and in addition, on the patient chest. Typically, the mean surface counts were 20-70 cfus/m2/h and the air counts 1-2 cfus/m3 in disposable clothing experiments, whilst the use of cotton clothing resulted in higher counts of 100-200 cfus/m2/h (wound P > 0.05, patient P > 0.05, instruments P < 0.01) and 4 cfus/m3 (P < 0.02-0.001). In the vertical LAF, taking both disposable and cotton clothing operations together, the surface and air contamination rates (surface/air ratio SAR) were highly correlated (P = 0.02-0.004) and the ratio varied between 18:1 and 50:1 with a mean for wound air of 36:1. Using only disposable clothing in the vertical LAF, the number of significant correlations was reduced. With cotton clothing experiments in vertical LAF and in the horizontal LAF using disposable clothing, no significant correlation between surface and air contamination was found. The wide variation of SAR values and the inconsistent relationship between surface and air counts indicates that measurement of OR air contamination represents an unhelpful method for assessment of surgical site contamination in LAF units. We propose instead that colony counts on sedimentation plates is a clinically more relevant indicator of bacterial OR contamination in LAF units. In addition to the current bacteriological standard for ultra clean OR air of (< 10 cfus/m3) we suggest a corresponding standard for the surface contamination rate of < 350 cfus/m2/h.

Correlation between surface and air counts of particles carrying aerobic bacteria in operating rooms with turbulent ventilation: an experimental study.

Airborne contamination with bacteria-carrying particles (cfu/m3) and their sedimentation rate (cfu/m2/h) was compared in an operating room (OR) equipped with two turbulent ventilation systems. One was a thermally based system with inlet of cool clean air at the floor level and evacuation of the air at the ceiling by convection (17 air changes/h). The other was a conventional plenum pressure system with air supply at the ceiling and evacuation at the floor level (16 air changes/h). The study was made during rigidly standardised sham operations (N = 20) performed in the same OR by the same six member team wearing non-woven disposable or cotton clothing. Airborne contamination in the wound and instrument areas was related to the surface contamination rate in the same areas and in addition, on the patient chest and in the periphery of the OR. With the exception of the periphery of the OR, the surface and air contamination rates were highly correlated in both ventilation systems (P = 0.02-0.0006, r2 = 0.52-0.79). This was also true particularly when disposable clothing was used while the correlation was weaker in cotton clothing experiments. An equation describing the relation between surface and air counts is given. Typically, the surface counts were numerically 16-fold the air counts, i.e., the number of colonies sedimenting on four 14 cm-diameter agar plates during 1 h will almost equal the number of airborne cfu per m3. We propose, that sedimentation plates represent not only a technically easier method than air sampling but when correctly used, are also the most realistic indicator of airborne bacterial OR contamination in areas critical for surgery.

Fragrance compounds and amphiphilic association structures.

Fragrance formulations have traditionally been based on alcohol as the solvent, but the recent legal restrictions on volatile organic solvents have prompted the industry to change to aqueous solubilized systems. The article reviews the fundamental factors in the application of such systems evaluating the influence by different amphiphilic association structures on the vapor pressure of fragrance compounds. This information is subsequently used to estimate the variation of fragrance compound vapor pressures during evaporation. The results reveal that the vapor pressure versus time variation is improved compared to solvent-based formulations.

Zoned exponential, vertical and horizontal ultra-clean laminar airflows. No differences in bacteriological efficiency.

We compared the novel zoned exponential ultra-clean operating room ventilation, needing no extra side-walls with the traditionally used ultra-clean air systems having vertical or horizontal laminar airflow, but requiring extra side-walls. The three units were evaluated with regard to elimination of particles with focus on airborne and sedimenting bacteria-carrying particles (colony forming units, cfu) during rigidly standardized sham operations. Although minor differences were recorded inside the ultra-clean airflows, the three systems were comparable with regard to bacteriological efficiency and ensured a low air and surface contamination (0.05-4 cfu/m3 and 7-72 cfu/m2/h, depending on the site of sampling). We conclude that all three systems fulfilled well the criteria for ultra-clean air (< 10 cfu/m3), but that exponential airflow is the most versatile alternative, as additional side-walls around the operating area can be omitted.

Vapour pressures of phenethyl alcohol and limonene in systems with water and Laureth 4.

The vapour pressures of phenethyl alcohol and limonene in their water-in-oil microemulsion region were measured by head space gas chromatography of equilibrated samples. The results showed that the vapour pressure of both fragrance compounds in their mutual solutions without surfactant or water was significantly greater than that in ideal solutions. The high vapour pressure of phenethyl alcohol in such solutions was strongly reduced by addition of the surfactant, Laureth 4, a commercial nonionic surfactant, approximately teteraethylene glycol dodecyl ether. Saturation of the solutions with water gave a further reduction in the vapour pressure. The high vapour pressure of limonene was not influenced to a corresponding degree; in fact, only a small influence was found. The results were interpreted as resulting from differences in intermolecular interactions due to location of the fragrance compounds in different parts of the colloidal association structures.