Monday, December 24, 2007

More for less with Toshiba's 40XF355D LCD

Even at 40in, the 40XF355 sporting Toshiba's ultra-slim 'picture-frame' takes up less space than the companies own 37in C-series LCD TV's.

Certainly with one eye on the visual impact of the 40XF355, the bezel of Toshiba's ultra-slim panel measures a mere 2.3cm wide. The dimensions also have the practical advantage of tempting consumers who would not normally have considered such a large screen.

The Toshiba 40XF355D is certainly not relying on its stunning profile to make its way in the world, as the spec sheet confirms. The 40XF355D sports a 10-bit panel for a broader range of colours along with a Full HD (1920 x 1080) resolution. It generously equipped with 3 HDMI as well as the usual component, Composite and S-video inputs.

As we expected with its similar spec, the performance of the 40XF355D is in many ways like the Toshiba 42X3030D. To get the negative out of the way, colours were often over-saturated with Standard Definition (SD) sources, and although we tweaked settings to achieve good results for any particular source, we could not find a setting we were content with in all situations.

Plug in a High Definition (HD) source however, and it becomes immediately apparent where this TV excels. HD pictures are quite sumptuous, with a sharpness and clarity that places it firmly in the leading pack of LCD TV's in this respect. Fast action sporting or movie action shows just how capable a screen this is. There is almost a total lack of motion judder, with one of the most natural looking fast action displays we have seen. Colours were deep and vibrant with a naturalism that was impressive in all situations whether the scenes were dark or bright.

Philips' Aurea LCD TV Shines

Taking 'Ambilight' technology to its most advanced point yet, the Dutch electronics giant Philips has introduced us all to its 'Aurea' technology on an LCD TV.

If the marketing blurb is to be believed, Philips is in the process of creating a sea change in the experience of viewing moving pictures in your own home, with their Executive Vice-President Rudy Provost calmly stating at this years IFA technology show in Berlin that Aurea is about providing - "a totally different home entertainment experience, one that addresses a consumer's emotional wellbeing, as much as providing a great entertainment platform"

In purely technological terms, Aurea technology is a little less profound, being an LCD TV with a luminous bezel which changes colour depending on what the screen is showing, an extension of Philips' 'Ambilight' technology.

Ambilight works by emitting coloured ambient light along the sides of the panel which is reflected on to the wall behind the TV. This 'ambient' light is determined by what is on the TV at any given time and Philips claim the effect is less eye strain with improved colour, detail and contrast.

Aurea builds upon ambilight with a fully back-lit LED which glows through the purpose built frame surrounding the LCD panel. With light actually shinning through the frame, Philips describes the effect as "bringing light and color to life in an unparalleled, highly visual and immersive fashion, drawing the audience into the full emotional experience".

Philips' 42in 42PFL9900D LCD with Full 1080p resolution and 8000:1 equipped with 'Aurea' technology is now available. Early indications are that picture quality is superb, but that the constantly changing frame of light around the screen is not to everyone's tastes.

While it remains to be seen whether or not Aurea can impress in the marketplace, Philips' ambilight technology has developed a growing following with highly acclaimed implementations on many of their LCD TV's.

LCD TV prices set to fall in 2008

There is a strong possibility that consumers could see the prices of large LCD TV's fall dramatically in 2008.

Overall, prices for LCD TV's as a whole are forecast to drop by around 11% from 2007 through 2008, with the greatest decreases being seen in the 40/42in and 50in category.

The average selling price for 32in LCD TV's is set to drop by a conservative 4% from December 2007 to December 2008. 37in panels are set to drop in price over the same period by almost 7%. 40in and 42in screens and above will show the biggest decreases of around 14%.

In the 40in + category competition between manufacturers is intense and this competition is being intensified with new entrants into the flat panel marketplace.

The Taiwanese LCD manufacturer ChiMei is just one example of a company who fancies grabbing a share of the higher end market for LCD TV's. ChiMei have recently begun production of 52in 1920 x 1080 panels believing they can undercut the likes of Sharp and Sony by as much as 50%.

The quality of ChiMei is not in doubt as they already supply some of the biggest names in the business. Depending on just how much extra capacity the Taiwanese company is planning to introduce, 2008 certainly seems to be shaping up as a good year for consumers, especially if you are planning to buy a large screen LCD TV.


The Z-DNA structure.
The Z-DNA structure.

Z-DNA is one of the many possible double helical structures of DNA. It is a left-handed double helical structure in which the double helix winds to the left in a zig-zag pattern (instead of to the right, like the more common B-DNA form). Z-DNA is thought to be one of three biologically active double helical structures along with A- and B-DNA.


Z-DNA was the first crystal structure of a DNA molecule to be solved (see: x-ray crystallography). It was solved by Alexander Rich and co-workers in 1979 at MIT.[1] The crystallisation of a B- to Z-DNA junction in 2005[2] provided a better understanding of the potential role Z-DNA plays in cells. Whenever a segment of Z-DNA forms, there must be B-Z junctions at its two ends, interfacing it to the B-form of DNA found in the rest of the genome.

In 2007, the RNA version of Z-DNA was described as a transformed version of an A-RNA double helix into a left-handed helix.[3]


B-/Z-DNA junction bound to a Z-DNA binding domain. Note the two highlighted extruded bases. From PDB 2ACJ.
B-/Z-DNA junction bound to a Z-DNA binding domain. Note the two highlighted extruded bases. From PDB 2ACJ.

Z-DNA is quite different from the right-handed forms. In fact, Z-DNA is often compared against B-DNA in order to illustrate the major differences. The Z-DNA helix is left handed and has a structure that repeats every 2 base pairs. The major and minor grooves, unlike A- and B-DNA, show little difference in width. Formation of this structure is generally unfavourable, although certain conditions can promote it; such as alternating purine-pyrimidine sequence, DNA supercoiling or high salt and some cations. Z-DNA can form a junction with B-DNA in a structure which involves the extrusion of a base pair.

Predicting Z-DNA structure

It is possible to predict the likelihood of a DNA sequence forming a Z-DNA structure. An algorithm for predicting the propensity of DNA to flip from the B-form to the Z-form, ZHunt, was written by Dr. P. Shing Ho in 1984 (at MIT). This algorithm was later developed by Tracy Camp, P. Christoph Champ, Sandor Maurice, and Jeffrey M. Vargason for genome-wide mapping of Z-DNA (with P. Shing Ho as the principal investigator).[4] Z-Hunt is available at Z-Hunt online.

Biological significance

While no definitive biological significance of Z-DNA has been found, it is commonly believed to provide torsional strain relief (supercoiling) while DNA transcription occurs.[5][2] The potential to form a Z-DNA structure also correlates with regions of active transcription. A comparison of regions with a high sequence-dependent, predicted propensity to form Z-DNA in human chromosome 22 with a selected set of known gene transcription sites suggests there is a correlation.[4]

Z-DNA formed after transcription initiation in some cases may be bound by RNA modifying enzymes which then alter the sequence of the newly-formed RNA [1].

Comparison Geometries of Some DNA Forms

Side view of A-, B-, and Z-DNA.
Side view of A-, B-, and Z-DNA.
The helix axis of A-, B-, and Z-DNA.
The helix axis of A-, B-, and Z-DNA.
Geometry attribute A-form B-form Z-form
Helix sense right-handed right-handed left-handed
Repeating unit 1 bp 1 bp 2 bp
Rotation/bp 33.6° 35.9° 60°/2
Mean bp/turn 10.7 10.0 12
Inclination of bp to axis +19° −1.2° −9°
Rise/bp along axis 2.3 Å (0.23 nm) 3.32 Å (0.332 nm) 3.8 Å (0.38 nm)
Pitch/turn of helix 24.6 Å (2.46 nm) 33.2 Å (3.32 nm) 45.6 Å (4.56 nm)
Mean propeller twist +18° +16°
Glycosyl angle anti anti C: anti,
G: syn
Sugar pucker C3'-endo C2'-endo C: C2'-endo,
G: C2'-exo
Diameter 26 Å (2.6 nm) 20 Å (2.0 nm) 18 Å (1.8 nm)