On the structural repertoire of pools of short, random RNA sequences

A detailed knowledge of the mapping between sequence and structure spaces in populations of RNA molecules is essential to better understand their present-day functional properties, to envisage a plausible early evolution of RNA in a prebiotic chemical environment and to improve the design of in vitro evolution experiments, among others. Analysis of natural RNAs, as well as in vitro and computational studies, show that certain RNA structural motifs are much more abundant than others, pointing out a complex relation between sequence and structure. Within this framework, we have investigated computationally the structural properties of a large pool (10 molecules) of single-stranded, 35 nt-long, random RNA sequences. The secondary structures obtained are ranked and classified into structure families. The number of structures in main families is analytically calculated and compared with the numerical results. This permits a quantification of the fraction of structure space covered by a large pool of sequences. We further show that the number of structural motifs and their frequency is highly unbalanced with respect to the nucleotide composition: simple structures such as stem-loops and hairpins arise from sequences depleted in G, while more complex structures require an enrichment of G. In general, we observe a strong correlation between subfamilies-characterized by a fixed number of paired nucleotides-and nucleotide composition. Our results are compared to the structural repertoire obtained in a second pool where isolated base pairs are prohibited. © 2008 Elsevier Ltd. All rights reserved.

Mask-less lithography for fabrication of optical waveguides

A flexible method for fabricating shallow optical waveguides by using femtosecond laser writing of patterns on a metal coated glass substrate followed by ion-exchange is described. This overcomes the drawbacks of low index contrast and high induced stress in waveguides directly written using low-repetition rate ultrafast laser systems. When compared to conventional lithography, the technique is simpler and has advantages in terms of flexibility in the types of structures which can be fabricated.

A joint approach to treating dental phobia:a re-evaluation of a collaboration between community dental services and specialist psychotherapy services ten years on

Objective To audit the records of a group of patients who had previously benefited from cognitive behavioural therapy (CBT) for dental phobia.Aim To ascertain if they had returned to the use of intravenous (IV) sedation to facilitate dental treatment. Ten years ago these patients were routinely requiring IV sedation to facilitate dental treatment due to severe dental phobia.Method Sixty patients entered the original pilot project. Of those, 30 were offered CBT and 21 attended. Twenty of those patients (95.2%) were subsequently able to have dental treatment without IV sedation. In this follow-up study the electronic records of 19 of the 20 patients who had originally been successful with CBT were re-audited. Our purpose was to see if there was any record of subsequent IV sedation administration in the intervening ten years.Results Of the 19 successful CBT patients available to follow-up, 100% had not received IV sedation since the study ten years ago. This may suggest the initial benefit of CBT has endured over the ten-year period.Conclusion This study indicates that the use of CBT for patients with dental phobia proves beneficial not only in the initial treatment but that the benefits may endure over time. This results in a significant reduction in health risks to the patient from repeated IV sedation. It may also translate into significant financial savings for dental care providers. Our evidence for CBT as treatment for dental phobia suggests dental services should be implementing this approach now rather than pursuing further research. © 2011 Macmillan Publishers Limited. All rights reserved.