We meet in Branford, CT, about once every 4-6 weeks and topics discussed range from physical sciences, to life sciences and social sciences. A knowledge of the topic being discussed is not required, nor is there any membership requirement or age restriction. Perhaps the only requirement is curiosity and a thirst for knowledge! Science and technology are integral to every aspect of life - history, geography, humanities, music - everything.
Now for a piece of excellent news for Tilde Cafe: as of January 23, 2009 you can find a link to us on the science cafes website maintained by WGBH Educational Foundation - WGBH is the public television station out of Boston, and produces NOVA among many other fantastic shows. Tilde Cafe is the only listed science cafe in CT, and the only one between NYC and Boston!
As of July 2014, the IRS has recognized Tilde Cafe as a 501(c)(3) organization. Gifts are deductible to the full extent allowable under IRS regulations.
© 2009 Deepti Pradhan and Tilde Cafe
Conceptually and structurally, every time you go out into the sun without sunscreen, you are likely to acquire mutations in the cells on your exposed skin. Most of these mutations occur because of an ultraviolet light induced chemical reaction that changes some of the building blocks that make up your DNA. In Texas, an hour of sun exposure at noon (without sunscreen) can result in up to 10,000 of these chemical reactions per cell. You probably recall from Professor Tom Pollard's cafe discussion back in 2009, that DNA is made up of four fundamental building blocks - A (adenine), G (guanine), T (thymine), and C (cytosine). A and G belong to the group of chemicals called purines; T and C belong to the group called pyrimidines. Pyrimidines, when exposed to UV light, undergo a chemical change within picoseconds, resulting in a new chemical - a cyclobutane pyrimidine dimer (CPD) - part of whose structure resembles the shape of a butterfly. If this UV induced alteration in your DNA isn't repaired by the cell's DNA repair enzymes in a timely manner, the change is passed on to the next generation of cells, and repeated cell divisions over the years can now result in a mass of cells that carry the mutation, and this mass could become either a benign or malignant tumor. Thanks to an extremely sophisticated and efficient DNA repair system, a very small number of alterations go unrepaired.
Sunlight includes light that encompasses a wide spectrum of energies. The human eye can't see light on either ends of the spectrum - ultraviolet is at the low end of the spectrum (and has high energy); infrared is at the high end of the spectrum (and has low energy). Although the ozone layer protects us from almost 99% of the UV radiation from the sun, the balance that reaches earth will be responsible for some of the 80,000 new skin cancer cases this year in the US. The most serious form of skin cancer develops in melanocytes, cells that produce melanin - the pigment that gives skin its color. While melanin has been known to confer some protection from sunburn and skin cancer, Professor Brash's recent research has demonstrated that the sun's UV radiation damages not only DNA at the time of sun exposure, but also affects the susceptibility of melanin to highly reactive chemical intermediates, resulting in melanin fragments that work like energy reservoirs. His research suggests that the fragmented and energized melanin transfers the energy to nuclear DNA, resulting in chemical changes in the DNA similar to those when directly exposed to the sun's energy.This latter process of DNA distortion that occurs in absence of sunlight, the dark reaction, is much slower: direct sunlight damage occurs in picoseconds (there are 60 trillion picoseconds in 1 minute). It is conceivable that with further research, currently available sunscreen can be supplemented or complemented with agents that might inhibit the DNA damage that continues even after the end of direct sun exposure.
This last talk of the seventh season competed with wonderful weather in Branford and a strong temptation to be out in the sun; we hope that those who were unable to attend were well protected from the UV rays! Thank you, Doug, for shedding light on the dark reactions occurring in our melanocytes. Something to consider for the summer then - if you're going to spend a lot of time out in the sun and you missed the cafe, you can view the video at the cafe channel in the next couple of days. And through the summer, please consider what Sid the Seagull tells Aussies to do - Slip, Slop, Slap, Seek & Slide. Australia has the highest incidence of skin cancer, with 2 out of 3 Australians being diagnosed with some form of skin cancer by the time they are 70 years old, so Sid should know.
Visit http://www.youtube.com/user/tildecafe for all cafe videos