Undergrad solves major hurdle to invisibility cloak

An undergraduate at the University of St. Andrews in Scotland has overcome a major hurdle in the development of invisibility cloaks by envisioning an optical device that would allow the cloak to hide things
against CHANGING backgrounds. The Institute of Physics and German Physical Society’s New Journal of Physics, published the study today, and the lead author, Janos Perczel, spoke with us about it from Hungary, via Skype,. But first — putting aside Harry Potter’s cloak of invisibility for a moment, in real life, scientists have cloaked some palm-sized objects . . . but not especially well.  …

… The sort of stuff you see in Harry Potter films has never been made yet. There have been experiments to test the theory but these experiments have always featured invisibility in some reduced form.

So far, cloaking only works when an object’s against one single field of steady background wavelength, like a “blue screen.” And even that’s complicated. “Cloaking” conceals an object by bending light around it. Perczel says it’s similar to putting a rock in a river, where the water bends around and covers the rock and makes it “disappear.. But just as water must speed up in order to hurry around the rock, bending light has required
accelerating the light. And super-speeded light flows too fast to allow a cloaking devices to adjust to changing backgrounds. In the new report, Perczel and colleagues offer a solution. They call it an invisibility sphere, and it buys enough time for the cloak to adjust to changing backgrounds by, well — what else? Their device slows down the normal speed of light. … It may be decades before this technology moves from theory to real world applications.  But Perczel predicts that there will be plenty. …

via Janos Perczel – Invisibility Cloak (Extended Version) | How On Earth.

Long term complications after adult braces

I’m about to get braces, but two people have told me they had cracked teeth, lost teeth and more periodontal disease after getting braces. I’m interested in the best long term tooth health, even into my 90s. My orthodontist does not think a person who takes care of himself will have these problems after treatment.

If you get braces, the roots of your teeth will shorten. Does this shorten the life of your teeth? Does it increase your risk of cavities? Does it increase the incidence of periodontal disease? So far, the answer to all three questions seems to be no. A New Zealand web site has these before and after images:

left: Pre treatment, right: Post treatment same patient: generalized root resorption

A central tenet of the Hippocratic oath is encapsulated by the phrase, ‘First, do no harm.’ As clinicians we must preserve this goal in all of our treatments, but even in the best of hands, and with every positive intention, this is not always possible. Root resorption is one of the few deleterious consequences of orthodontic treatment and perhaps the most commonly suffered, if not actually seen. The clinician who claims that this never happens to his patients just isn’t taking good enough post-treatment records. Even though there is a paucity of studies examining long-term survivability of root-resorbed teeth (Lee et al, 2003) it would appear unusual for the amount of resorption from orthodontic treatment to produce a reduction in the life of a tooth. Premature tooth loss has not been reported in the literature (Killiany, 1999).

… Orthodontists are principally interested in External Apical Root Resorption (EARR), which is a form of surface resorption. …

The incidence of EARR shows a wide range of reporting, with histological studies showing a higher incidence than clinical studies. Females are more susceptible than males (Linge and Linge 1983). The most readily affected sites are (in order) maxillary laterals, maxillary centrals, mandibular incisors, the distal root of mandibular first molars, mandibular second premolars and maxillary second premolars (Brezniak and Wasserstein, 1993). The risks of resorption do seem to increase after the age of 11 years (Linge and Linge, 1983). …

Unfavorable and detrimental EARR is thought to occur in 3-5% of orthodontic patients with mean losses of between 1 and 2mm (Kennedy et al, 1983). However, because of its unpredictable nature and difficulty in detection if small, the incidence may be much higher. In the majority of patients root loss is limited to 2mm or less (Sameshima and Sinclair, 2001) …

The finding of EARR is a common sequalae to orthodontic treatment. As such it needs to be part of the informed consent process. Fortunately, it is rare that root resorption is ever extensive enough to cause any detrimental effect for the patient. In the vast majority of cases root resorption will continue to be a finding that only the researcher or occasionally the orthodontist will notice on post treatment radiographs. … – link

There is a small negative effect on your gums according to this study:

The Effects of Orthodontic Therapy on Periodontal Health – A Systematic Review of Controlled Evidence

… Weak evidence from one randomized study and 11 nonrandomized studies suggested that orthodontic therapy was associated with 0.03 millimeters of gingival recession (95 percent confidence interval [CI], 0.01–0.04), 0.13 mm of alveolar bone loss (95 percent CI, 0.07–0.20) and 0.23 mm of increased pocket depth (95 percent CI, 0.15–0.30) when compared with no treatment. The effects of orthodontic therapy on gingivitis and attachment loss were inconsistent across studies.

… The existing evidence suggests that orthodontic therapy results in small detrimental effects to the periodontium.   – jada

Here are some additional before and after x-rays:

On 28th SEPTEMBER 2010:

On 24th MAY 2011:

… isn’t it amazing what 8 months of orthodontic treatment can do? – gracemagg

It looks to me like there are now channels leading down the sides of the teeth that were moved the most (since bone does not re-grow). Does this fill in to prevent bacteria from getting down there?

Are teeth moved by braces more likely to end up with an infected root?  If the space at the bottom of the roots becomes infected and fills with pus, this is known as a tooth abscess which can kill you if untreated when the infection attacks your heart through the blood stream.  I’ve had 5 teeth extracted, however, and have have had only minor problems with inflammation of the jaw where I have a complete lack of tooth roots.

Conclusion: There are risks, but I believe that if I maintain good overall health, that I will be fine, and that I will be happier for the remaining years of my life having a nice smile.

If you are in your 60′s, 70′s, 80′s or 90′s and you had braces after you were 35 years old, do you still have all your teeth? Have you had any periodontal disease which only started after you had braces?

Apollo 18 Official Trailer (2011)

Apollo 18 Official Trailer (2011) – HD – YouTube.

Explorer Marco Polo ‘never actually went to China’

Marco Polo’s journeys to China and the Far East established him as one of history’s greatest explorers but archeologists now believe he never actually went there.

They think it more likely that the Venetian merchant adventurer picked up second-hand stories of China, Japan and the Mongol Empire from Persian merchants whom he met on the shores of the Black Sea – thousands of miles short of the Orient.

He then cobbled them together with other scraps of information for what became a bestselling account, “A Description of the World”, one of the first travel books.

The archeologists point in particular to inconsistencies and inaccuracies in his description of Kublai Khan’s attempted invasions of Japan in 1274 and 1281.

“He confuses the two, mixing up details about the first expedition with those of the second. In his account of the first invasion, he describes the fleet leaving Korea and being hit by a typhoon before it reached the Japanese coast,” said Daniele Petrella of the University of Naples, the leader of an Italian archeological project in Japan.

“But that happened in 1281 – is it really possible that a supposed eye witness could confuse events which were seven years apart?” …

via Explorer Marco Polo ‘never actually went to China’ – Telegraph.

Sunken Treasure Found in the Seas Of Sicily

Italian archaeologists have retrieved a sunken treasure of 3,422 ancient bronze coins in the small Sicilian island of Pantelleria, they announced today.

Discovered by chance during a survey to create an underwater archaeological itinerary,the coins have been dated between 264 and 241 BC.

At that time, Pantelleria, which lies about 70 miles southwest of Sicily, in the middle of the Sicily Strait, became a bone of contention between the Romans and Carthaginians.

Rome captured the small Mediterranean island in the First Punic War in 255 BC, but lost it a year later.

In 217 BC, in the Second Punic War, Rome finally regained the island, and even celebrated the event with commemorative coins and a holiday.

via Sunken Treasure Found in the Seas Of Sicily : Discovery News.