Remembering 2010 Iceland Volcanic Ash

DATE FRIDAY 16, 2010. TIME 16 HOURS

START FROM GOTHENBURG SWEDEN TO LONDON UK.

ENTERING DENMARK

ENTERING GERMANY

ENTERING NETHER LAND

ENTERING BELGIUM

ENTERING FRANCE- DIRECT TO Z1 DU PORT DUNKERQUE

ENTERING UK- DOVER PORT TO DOVER TRAIN STATION

REACH ST. PANCRAS INTERNATIONAL ON SATURDAY 17. 2010 8.30 HOURS. 1600KM

l AM BEING HOLD BY BRITISH M16 OUTSIDE ST. PANCRAS INTL TRAIN STATION

SUSPECTED ME AS TERRORIST, BUT THEN THEY LET ME GO SINCE I GOT NOTHING ON ME . MEET ENGLAND PM GORDON BROWN OUT SIDE THE TRAIN STATION.

PM IS ON HIS ELECTION CAMPAIGN VISITING PUBLIC AT THE TRAIN STATION.

ALL BECAUSE OF VOLCANIC ASH FROM ICELAND.

SPR Navi 200 specification

SPR Navi 200 specification

1. True goniometric principle, enabling to record the full SPR curve for thickness and refractive index model-ing

2. Wide SPR angle range (40 degrees to 78 degrees) allowing to measure both liquid and gas samples with the same instrument

3. Proprietary SPR slide holder allowing easy change and use of SPR gold slides

4. Easy drop-in action in placing the SPR slide in the instrument

5. Easily removable and easily customizable flow cell

6. Modular design allowing to add an autosampler and other features, such as multi wavelength function, at the later stage

7. No need to use messy and inconvenient index matching oil because of the proprietary index matching gel

8. Open design allowing the customer use their own fluidics and flow control (our pump can easily be by-passed)

9. Build in peristaltic pump and optional syringe pump available

10. Easy to use slide holder allowing quick and easy slide replacement without any tools

11. External immobilizer allowing the instrument be used while immobilizing the gold surfaces

12. Possibility to use two lasers with different wave lengths and/or even IR lasers

13. Optional electrochemistry flow cell

Contact Angle meter/Gonimeter: Theory

Contact Angle: Theory

The following is a short introduction to the concepts involved in the measurement of contact angles. Included is an introduction to the techniques involved and some practical advise. For those interested in further information a list of references appears at the end of this chapter.

What is contact angle?
Contact angle ,q, is a quantitative measure of the wetting of a solid by a liquid. It is defined geometrically as the angle formed by a liquid at the three phase boundary where a liquid, gas and solid intersect.

It can be seen from this figure that low values of q indicate that the liquid spreads, or wets well , while high values indicate poor wetting. If the angle

q is less than 90 the liquid is said to wet the solid. If it is greater than 90 it

is said to be non-wetting. A zero contact angle represents complete wetting.

Hysteresis: For any given solid / liquid interaction there exists a range of contact angles which may be found. The measurement of a single static contact angle to characterize the interaction is no longer thought to be adequate. The value of static contact angles are found to depend on the

recent history of the interaction. When the drop has recently expanded the angle is said to represent the ‘advanced’ contact angle. When the drop has recently contracted the angle is said to represent the ‘receded’ contact angle. These angles fall within a range with advanced angles approaching a maximum value and receded angles approaching a minimum value.

The difference between the maximum(advanced) and minimum(receded) contact angle values is called the contact angle Hysteresis. A great deal of research has gone into analysis of the significance of hysteresis. It has been used to help characterize surface heterogeneity, roughness and mobility. You are recommended to the papers listed in the reference of this section for details on experiments regarding hysteresis.

Contact angle can also be considered in terms of the thermodynamics of the materials involved. This analysis involves the interfacial free energies between the three phases and is given by:

g_lv cos q = g_sv - g_sl

where g_lv ,g_sv and g_sl refer to the interfacial energies of the liquid/vapor, solid/vapor and solid/liquid interfaces.

Coatings: Coatings may be applied to any solid for testing contact angles. Microscope slides and cover slips make ideal supports for such an application. Ideally the coating should be applied to all sides. If you reduce the size of your sample by cutting after coating you will expose part of the support which is not coated. This will introduce an error in your data especially if the cut side is rough. Your data may be consistent enough to compare between similarly treated samples but the absolute values will not be accurate.

Tensiometer Kulim Kht

Installation in Malaysian Top University complete system

Potentiostat LPR technique

The LPR technique is the most frequently used being both quick and easy. A small sweep from typically -10 mV to +10 mV at 10 mV/min around the rest potential is performed. The resulting current/voltage plot usually exhibits a straight line the inverse slope of which is proportional to the corrosion rate. The Gill AC Gill 8 and 12 the Field Machine the Pocket Machine the LPR meter and the Bubble Test software all use this method.

Kulim Kht Contact Angle/Goniometer

Captive bubble method in contact lens studies

Contact lenses are widely used and hydrogel contact lenses are the most

prescribed type of contact lenses around the world. Hydrogel lenses are made from

hydrophilic polymers, such as polyhydroxyethyl. Contact lenses should have certain

characteristics to avoid discomfort during wear. These include an adequate oxygen

permeability, lens motion and surface wettability. A fairly recently discovered

material for contact lens manufacturing is the silicone hydrogel, which is suitable for

long term use as it has improved oxygen delivery on the ocular surface. However,

this material has been reported to have reduced wettability compared to the other

materials used in hydrogel contact lenses.

The wettability of a lens is measured on the abilities of the lens to support a

continuous and rupture-resistant tear film on its surface. A lens with a limited

wettability is uncomfortable and has a reduced visual performance. Therefore it has

been a major investment for the contact lens industry to develop a soft lens surface

that is highly wettable in the ocular environment.

How to study the wettability of contact lenses?

Contact angle measurement is the most common method used to characterize

wettability of solid surfaces. There are a variety of contact angle techniques that can

be used for this purpose: the sessile drop method and the captive bubble method.

Sessile drop and captive bubble methods can also be used simultaneously to

measure the different contact angles of a lens. Sessile drop method can be used to

examine the advancing contact angle and captive bubble method to obtain the

receding contact angle. Both of these contact angles can also be obtained only by

captive bubble method. Captive bubble method is very useful as it is possible to

maintain fully hydrated conditions on the lens surface during the experiment. This is

essential as the drying of the lens causes the setup to be far from the ideal

conditions. Figure 1a illustrates the sessile drop method, where a drop of water is

replaced on a glass slide. The contact angle obtained with this method was 140°. In

Figure 1b the contact angle of an air bubble in water is obtained with the captive

bubble method and it is calculated to be 40°. Contact angle hysteresis is the

difference between the advancing and receding contact angles. It can be used to

characterize the surface roughness, chemical heterogeneity, re-arrangement of

molecules at the surface, solid swelling and mobility. In highly water wetting lenses

the contact angle hysteresis is eliminated and both the advancing and receding

contact angles approach zero.

Captive bubble technique

In the captive bubble method the contact angle is measured by placing a bubble of

air onto the lens surface with a capillary while the lens is immersed in a liquid.

Preferably the lens should be soaked in liquid for a couple days before the

measurement takes place in order to get the lens fully wet. The conditions in this

experiment should mimic the in vivo conditions as good as possible, meaning that

the liquid used in the contact angle experiments should be close to the real nature

of a tear film in the eye. The tear film is composed of surface active components

such as mucin and lysozyme.

Receding and advancing contact angles are both important measures of contact

lens wettability. A receding angle forms as the water phase moves away from the

capillary. This corresponds to the situation when the eyelid is open and the tear film

starts rupturing on the lens. The advancing contact angle develops as the water

phase moves towards the capillary. This is the case when the eyelid closes and the

tear film on the lens starts to recover.

A solution for finding improved wettability?

With captive bubble method contact angles of lenses can be measured in different

solutions to obtain the most ideal solution that wets the lens best. Some have

reported that significant change can’t be seen in whether the solution is pure water

or a liquid containing surfactants (like the contact lens solutions on the market).

Also studies of different coatings to improve the lens wettability have been made.

Protein coatings have found to be successful in improving the wettability of contact

lenses. Protein coatings resist the tear protein adsorption and deposition into the

lens.

Biolin Q-Sense Kulim Kht QCM-D

QCM-D Technology

By collecting both the dissipation and the resonance frequency of a quartz crystal,
QCM-D technology can be used to characterize the formation of thin films (nm) such as proteins, polymers and cells onto surfaces, in liquid. This is QCM-D, Quartz Crystal Microbalance with Dissipation monitoring, Q-Sense's proprietary sensor technology.

In liquid, an adsorbed film may consist of a considerably high amount of water, which is sensed as a mass uptake by all QCMs. By measuring several frequencies and the dissipation it becomes possible to determine whether the adsorbed film is rigid or water-rich (soft) which is not possible by looking only at the frequency response. The amount of water in an adsorbed film can be as high as 95% depending on the kind of molecule and the type of surface you are studying. Picture elongated molecules - if they would adsorb flat on the surface, little water will be coupled to the molecules. However, if they adsorb standing up at the surface, lots of water will be coupled. With QCM-D the kinetics of both structural changes and mass changes are obtained simultaneously.

Would you like to ask specific questions or gain more information about the QCM-D technique? You are welcome to contact us at any time.

The QCM-D Principle
Unlike all other QCMs, QCM-D monitors the response of the freely oscillating crystal, which is faster and more accurate than the usual frequency sweep principle.