Stories tagged Life Science

Dec
10
2011

The sunflower and the bee: just the kind of photograph Project Noah likes to see.
The sunflower and the bee: just the kind of photograph Project Noah likes to see.Courtesy Mark Ryan
I saw a posting on Facebook yesterday (tip of the hat to the Bell Museum) about a website called Project Noah. It’s a really cool site that allows anyone with a camera and a love of nature to upload pictures or video and help identify the plants and animals that populate our world, both locally and globally. And who doesn’t have a camera of some sort nowadays?

Anyway, according to their website Project Noah is:

"… A tool that nature lovers can use to explore and document wildlife and a technology platform research groups can use to harness the power of citizen scientists everywhere. The purpose of the project is to mobilize and inspire a new generation of nature lovers. It began as an experiment to see if we could build an app for people to share their nature sightings and has evolved into a powerful global movement for both amateurs and experts. The name “Noah” is an acronym that stands for networked organisms and habitats. “

That kind of sums it up. The site is easy to navigate and figure out. I uploaded a couple photos I’d taken recently and it wasn’t difficult at all. You can also join a “mission” dealing with a particular zoological or botanical subject you’re interested in. You can contribute to the mission’s knowledge base by adding your own photographs or some information such as the genus and species of an unknown specimen captured in someone else’s photograph. I like shooting photographs up around Lake Superior so I joined the “Great Lakes Monitoring” mission. It just took a click of a button to become a part of it.

You can even start your own mission. It could be a legitimate study you’ve devised like why "megapug" bees seek out sunflowers or something as simple as a call for the best wildlife photos of the year. Here at the Science Museum we could start a mission called Rotting Pigs. I wonder how many contributions that would garner?

As mentioned, there’s even a Project Noah app that you can download for the mobile device of your choice. I downloaded it for my iPod Touch but noticed the reviews for it seem to be mixed. It only got an average rating overall, but what the hey, it’s free so I’m giving it a shot anyway. You can do the same if you'd like. I already know the site works fine on my laptop.

I’m really excited about this. It’s a novel and cool way to intermingle our ever-changing networking technologies with the rest of the natural world, and contribute something to the science community at the same time.

If you have more questions you might find the answers on Project Noah’s FAQ page.

LINKS
Project Noah

Nov
16
2011

In this video renowned paleontologists Bob Bakker and Peter Larson visit the CK Preparations lab in Montana to examine the incredible discovery by Clayton (“Dino Cowboy”) Phipps of the remains of a tyrannosaurid and some sort of ceratopsian dinosaur preserved together (and touching) in a single block of rock from the Hell Creek Formation. Both skeletons are articulated, nearly 100 percent intact, and in a wonderful state of preservation. Teeth matching those remaining in the tyrannosaurid jaws are preserved imbedded in the ceratopsian skeleton. The predator’s skull, which is speculated to be that of a Nanotyrannus, shows signs of being kicked in. Early analysis of the geology of the matrix encasing the find suggests that the two battling dinosaurs may have gotten trapped in mire or overcome by a sudden environmental catastrophe, like a cave-in. Was this a unique moment frozen in time of a battle between a predator and its prey? Do the two "combatants" represent entirely new genera of dinosaurs? These questions require further study and preparation of this very unusual fossil.

Smithsonian’s “Tracking Dinosaurs” site
Paleo-Incident Project

Nov
07
2011

I posted this picture a few days ago on Facebook and got a ton of comments. Apparently, I am not the only one that does this. I also thought this was something new, but a friend pointed out that I did this since I was 14 (9th grade sleepovers). My husband is really creeped out by it and he has to physically push my arm back down. Has anyone else ever experienced this? Does anyone know what causes this? The human body sure does weird things!!

Weird Sleeping Habit
Weird Sleeping HabitCourtesy My Husband

Nov
04
2011

Another Experimonth I am working on is "My how you have grown". I started out by posting a recent picture of me:
Recent Photo of Myself: Here is a picture of me on Halloween 2011.  Obviously I was Freddy Krueger :)
Recent Photo of Myself: Here is a picture of me on Halloween 2011. Obviously I was Freddy Krueger :)Courtesy My Husband

From there the converstation went into Horror Movies, favorites, and what we like about them. I mentioned that I like being scared and that adrenaline rush you get from the suspense. I didn't put any thought into why until I received this comment:

"Kiki, do you think your "need for scary/adrenaline rushes" is a result of genetics or your environment growing up?"

My head started spinning!! I needed to respond right away because I never thought about the things I do now being a reflection of either genetics or my environment. So, I responded immediately. This is what I wrote:

"ooohhh, good question!! Most "people" would say it probably stems from my parents divorce when I was 10. Until I left for college,I had to deal with my parents crazy relationships (my parents got along with each other fine, it was their boyfriends/girlfriends that was crazy). I guess I really never had "normal" growing up, so I like horror/suspense movies because they aren't "normal".
I love goofy/raunchy comedies as well, but NOT romantic comedies (unless the couple does NOT end up together). I find romantic comedies fake (yeah, i know, a pot calling the kettle black)....I get so mad when they end up together in the end because in the real world, that isn't how it works. It frustrates me and I actually get angry at the movie!! Blue Valentine was good because (spoiler alert!) they didn't end up together.
So there is my environmental factor in a nutshell....however, I do believe that there is genetics involved as well. My mom loves Dean Koontz (horror/suspense novelist) and my dad loves crime books. I am the only one in the family though that takes it to an extreme, but that is the way I am, no gray area, all black and white.
A psychologist would love this right now. haha
That was all just a quick blurb off the top of my head, however, that question was really good and i will be thinking about this for awhile!!"

Now, like I said, this is all off the top of my head and I really want to spend more time thinking about this as I find it extremely interesting. So, the reason for my blog isn't just to share my thoughts, but also get thoughts from others on either my response above or what they think about genetic vs environmental factors playing a role in their current life.

Nov
04
2011

Teeth tell tales of travel: Ratio of oxygen isotopes in Camarasaurus teeth reveals that the sauropod migrated long distances to find food and water. Geological Museum, University of Wyoming, Laramie, WY
Teeth tell tales of travel: Ratio of oxygen isotopes in Camarasaurus teeth reveals that the sauropod migrated long distances to find food and water. Geological Museum, University of Wyoming, Laramie, WYCourtesy Mark Ryan
Ever wonder how something as big as a sauropod dinosaur was able to grow so large? Sauropods were those huge, long-necked quadrupeds estimated to have weighed anywhere from 50 to 120 tons, and with lengths of up to 200 feet. Just seeing the skeleton of any one of them – the Apatosaurus, Diplodocus, Brachiosaurus, Ultrasaurus or any their kind – you just know those Jurassic giants had to be on a constant eating binge to maintain their massive size. But just how much food could a single area supply? Doesn’t it make sense that these critters would have eaten up any food source within the reach of their extensive necks? Then what would they do?

A new study of sauropod teeth has produced some strong evidence that the giant herbivores migrated during times of drought or other environmental stresses, searching for new untapped food and water sources. Geochemist Henry Fricke of Colorado College in Colorado Springs along with student colleagues Justin Hencecroth and Marie E. Hoerner studied the teeth of various Camarasaurus specimens comparing the ratio of oxygen isotopes found in the enamel with the ratio found in the sedimentary rock deposits where the teeth were found. By sauropod standards, Camarasaurus was one of the smaller ones, but it's the most common sauropod found in the Morrison Formation deposits.

Camarasaurus skeleton
Camarasaurus skeletonCourtesy Public domain
During its lifetime 145 million years or so in the past, a Camarasaurus's teeth would absorb the isotopes ratio of its environment, that is the ratio of the oxygen isotopes found in the local water supply. So Fricke’s team sampled 32 camarasaur teeth, taking measurements of the younger enamel found near the base of each tooth with the older enamel near the crown. In some cases, the isotopes ratios in the enamel matched those of the sedimentary rocks from where the teeth were found. But some enamel didn’t match. This meant the dinosaur must have migrated at some time to higher ground, more than likely in search of a better food source.

"In a theoretical sense, it's not hugely surprising,” Fricke said. “They are huge — they would probably have eaten themselves out of house and home if they stayed in one place.”

So the camarasaurs did what any hungry animal would do: they headed out in search of more food, even if it meant a migration of 200 miles into the higher regions and back. Seasonal droughts were probably another factor. The highlands would have had more rainfall and therefore more vegetation and water. When the wet season returned to the basin so would the camarasaur herds. Fricke estimates the seasonal herbivore hikes took around five months to complete. He also thinks if one kind of sauropod migrated, other genera probably did the same, and an analysis of their teeth would probably show similar results.

SOURCES and LINKS
Abstract in Nature
Nature News
Paleoclimatology: the Oxygen Balance
Camarasaurus facts

Oct
27
2011

Sometime on or around October 31st, the world's population will hit seven billion people.

Population map: A map from the Worldmapper World Population Atlas: www.worldpopulationatlas.org (c) Sasi Research Group, University of Sheffield
Population map: A map from the Worldmapper World Population Atlas: www.worldpopulationatlas.org (c) Sasi Research Group, University of SheffieldCourtesy Worldmapper.org / CC BY-NC-ND 2.0

(There are a lot of challenges to supporting seven billion people. Want to know more about that? Check out the University of Minnesota's Institute on the Environment, where folks are working to find solutions to some of those problems.)

That's all fascinating and all, but...what about me? Luckily, the BBC has come to the rescue with a lovely little interactive that's, well, all about me. Or you. Whatever.

For example, according to the BBC calculator,

  • At the time of my birth, I was the 3,840,942,641st person to live on Earth.
  • And the 78,068,048,685th person to live since history began.
  • This morning, the United States has a population of 311,284,287 people,
  • In the US, there are 484 births, 288 deaths, and a gain of 113 immigrants every hour, for a total average yearly population growth of 0.9%. (The country with the fastest growing population is Qatar, experiencing an increase of 514 people every day. The country with the fastest shrinking population is Moldova, experiencing a decrease of 106 people every day.)
  • As a woman in the United States, I can look forward to an average life expectancy of 80.5 years. Men in the US, however, enjoy an average life expectancy of only 75.4 years, dragging the US total average down to 78 years. Thanks, men. (The Japanese have the longest average life expectancy in the world, at 82.7 years, while folks in the Central African Republic have an average life expectancy of only 45.9 years.)

Not too shabby!

To give you a sense of just how fast our population is growing, here's a crazy little fact: by mid-century, the world's urban population will equal the size of the world's global population in 2004. Wow. Cities are efficient, and concentrate us so that we can use land for other purposes, but they're also ecological hotspots. Curious about how your household measures up? Try the household flux calculator, or check out the Q&A with Scientist on the Spot Daniel Nidzgorski.

Not enough for you? Check out "Seven billion in seven stories" and "Will people numbers keep rising?"

Oh, and let us know: #whatsyournumber ?

Oct
26
2011

Danse Macabre: Artwork Inspired by the Black Plague.
Danse Macabre: Artwork Inspired by the Black Plague.Courtesy Wikimedia Creative Commons
Halloween is coming up soon and what better way to scare the tar out of everybody than with another Black Plague story.

Researchers from Germany and Canada have now determined that the pathogen existing today that infects the human population with bubonic plague is the same one that caused the horrific pandemic known as the Black Plague (aka Black Death) during the Middle Ages,

In the 14th century (1347-1351) the the plague devastated much of Europe. It was brought on by the bacterium Yersinia pestis and thought to have originated in China. Rats, infested with fleas carrying the bacteria, spread the fatal pathogen via the trade routes and across Europe, wiping out one-third of the human population. This is a conservative estimate; some claim as much as 60 percent of the population was eradicated!

Whatever the case, imagine even a third of all your acquaintances, friends, and relatives suddenly dying from what one 14th century chronicler described as “so virulent a disease that anyone who only spoke to them was seized by a mortal illness and in no manner could evade death.”

And it was an extremely horrible death, to say the least, as Michael Platiensis makes clear in his writings from 1357:

“Those infected felt themselves penetrated by a pain throughout their whole bodies and, so to say, undermined. Then there developed on the thighs or upper arms a boil about the size of a lentil which the people called "burn boil". This infected the whole body, and penetrated it so that the patient violently vomited blood. This vomiting of blood continued without intermission for three days, there being no means of healing it, and then the patient expired.“

[Above quoted in Johannes Nohl, The Black Death, trans. C.H. Clarke (London: George Allen & Unwin Ltd., 1926), pp. 18-20]

The Black Plague was the second of three great waves of plague that raged across Europe during historical times. The first, known historically as the Plague of Justinian, took place in the 6th century and affected the Byzantine Empire and much of Europe. The last major wave, known as the Great Plague of London, killed about 100,000 of the city’s population in 1664-65. In the two centuries that followed, waves after wave of the plague continued to devastate the European population although on a lesser scale. These outbreaks although sometimes as virulent, were often more isolated regionally or within a city and kept Europe’s population from rebounding for a good century and a half.

The plague presents itself in three ways: bubonic, septicemic, and pneumonic. All three infections are caused by Y. pestis. With bubonic plague, the lymph nodes become painfully swollen into what are termed buboes – hence the name bubonic. Scepticemic plague, the rarest of the three forms, infects the blood. Both bubonic and scepticemic, if left untreated, result in death between 3-7 days after infection. Pneumonic is the most contagious since it infects the lungs and is easily spread through the air in a spray of water droplets. It’s also the most lethal and usually kills its victims in one to three days. Each form can present itself on its own or can progress into all three. It’s thought the Black Plague was mainly a combination of the bubonic and pneumonic forms. (The practice still used today of saying, “Bless you” after someone sneezes is a holdover from the 14th century plague) The only defense against the pandemic was avoidance of fleas and the fatally sick. Not easy to pull off when rats and the afflicted were widespread. Infected families were generally quarantined, their houses marked with a red cross, and left to fend for themselves.

The plague had a tremendous effect on European life in the Middle Ages. The Hundred Years’ War actually paused briefly in 1348 for lack of soldiers. The plague had wiped out too many of them. Economically, wages rose sharply because the workforce was also greatly reduced. Shop owners suffered because no one dared step outside the confines of their own homes, so supplies rose and prices dropped. The removal of the rotting corpses required relatives either doing it themselves and further risking infection, or paying premium prices for some other poor schlub to do it. The dead were buried as quickly as possible, often in mass graves.

In the recent research which appears in the Proceedings of the National Academy of Sciences, Dr. Johannes Krause and his colleagues extracted DNA from the tooth enamel of five corpses from one of these 14th century mass burial sites in London (under the Royal Mint!). Using the latest technology to sequence the DNA fragments, the researchers from the University of Tubingen in Germany, and McMaster University in Canada, decoded a circular genome called pPCP1 plasmid that comprises about 10,000 positions in the Y. pestis DNA. When they compared it with the genome of the pathogen’s current strain, the genetic information appeared to have changed very little over the past six centuries. (It should be noted that the researchers suspect the pathogen that occurred in the 6th century may have been a now-extinct strain of Y. pestis or one completely unrelated to bubonic plague.)

So, that means the very same nasty contagion – the one that terrorized and devastated so much of Europe for so many centuries in the Middle Ages - is still with us today. Luckily, the bubonic plague can be held at bay with antibodies if treated in time. But what happens if Yersinia pestis mutates into a strain against which current antibodies are useless? If that doesn’t make the hair on the back of your neck stand on end, I don’t know what will.

Happy Halloween!

SOURCES and LINKS
Scientific Computing story
The Black Plague by Dr. Skip Knox, Boise State
Plague symptons and signs – in case you get it
Nifty Black Death quiz – thanks Liza!

Oct
15
2011

Giant bison skull: its horns spanned 6 feet 4 inches. Behind stands Dr. Steve Holen, curator of archaeology at the Denver Museum of Nature & Science
Giant bison skull: its horns spanned 6 feet 4 inches. Behind stands Dr. Steve Holen, curator of archaeology at the Denver Museum of Nature & ScienceCourtesy Photo by Heather Rousseau ©Denver Museum of Nature and Science
The last talk I attended at the Geological Society of America (GSA) convention this past week was one of my favorites. It was an update of the Snowmastodon Project given by Kirk Johnson, chief curator at the Denver Museum of Nature and Science (DMNS). Just one year ago, a construction worker bulldozing for a dam-building project at the Zeigler Reservoir near Snowmass Village in Colorado unearthed a mammoth tusk. Paleontologists and archaeologists from the Denver museum were called in, and excavation of a small portion of the drained reservoir bottom soon got underway. The museum crew worked for just one month, until November 14, 2010, when snowfall halted the project. Then last spring scientists returned to the site and were allowed just 51 days to excavate the fossil deposits before the Snowmass Water and Sanitation District resumed their expansion work on the reservoir.

This time more research experts from the US, Canada, and England joined the dig along with a slew of interns and volunteers, totaling some 233 people working on the project. Over the next seven weeks excavation at the Zeigler Reservoir site progressed at a frantic pace. According to Johnson, anywhere from 15 to 90 diggers were on site each day digging out fossils from the ancient peat and mud deposits, from what once were the shores of a small glacial lake. Despite the short window of opportunity, the sheer number and diversity of fossils from the dig site has been truly remarkable.

American Mastodon: (Mammut americanum)
American Mastodon: (Mammut americanum)Courtesy Dantheman9758 at en.wikipedia
Of the nearly 5000 bones and skulls exhumed from the Snowmass fossil site, more than 60 percent were of mastodons (Mammut americanum) representing at least 30 individuals in various stages of life. The other 40 percent of the fauna included mammoths (Mammuthus columbi), camels, horses, giant bison (Bison latifrons) and ground sloths (Megalonyx jeffersonii), otters, muskrats, minks, bats voles, chipmunks, beavers, bats, rabbits, mice, salamanders, frogs, lizards, snakes, fish, and birds, and iridescent beetles. No large carnivore remains were found in the deposits, and human remains were absent as well, although archaeological techniques were used during the dig just in case any were uncovered.

Flora from the prehistoric tundra environment included pollen, green leaves and cones, and tree logs, some with their bark still intact.

So far, age estimates for the deposits range between 43, 000 to 130,000 years old although further dating tests should narrow that down.

The talk included several photos of what Johnson termed “Flintstone moments”, i.e. shots of field workers posing with massive mammoth or mastodon femurs or tibia. And Johnson marveled at the incredible state of preservation of many of the fossils displayed. Some of the bones, he said, still emitted a very strong funk.

In terms of sheer number of bones and ecological data, Snowmastodon ranks up there as probably one of the best high altitude Ice Age ecology sites in the world, and certainly the best mastodon fossil site. A team of researchers at the DMNS lab will spend the next year and a half cleaning, cataloging, and analyzing all the fossils found at the Snowmass dig site, water was to be reintroduced into the reservoir on Oct. 13. Despite the loss of the site, the field crew did a tremendous job in the time they were given to excavate the fossil-rich site. And Kirk Johnson didn’t hide his excitement. In closing his talk, he said “It was one hell of a year!”

FURTHER INFO
The Snowmastodon Project website
Photo set on Flcker

Sep
22
2011

Achatina fulica: the giant African land snail.
Achatina fulica: the giant African land snail.Courtesy motnworb
We’ve seen it before. Through the years the human race has had to endure attacks by giant creatures of all sorts.

First, a humongous lizard larger than any known dinosaur crushes Tokyo and incinerates the rubble with his bad breath. Then super-sized spiders from another dimension terrorize northern Wisconsin only to be reduced to sludge by clever scientists. Later, gigantic ants run amok in New Mexico destroying property and people until the US Air Force, Navy, AND the Army are called in to destroy them. And now on top of all that, there are reports that large numbers of giant snails are terrorizing south Florida. When will this madness end?!

Of course the first three examples are pure fiction. Godzilla never really existed, spiders from another dimension can’t enter ours through wormholes, and the idea of gigantic ants is just stupid. But unfortunately the giant African snails infesting south Florida are all too real. And as you can see by the accompanying photo these suckers are huge. Some can grow up to 15 inches in length and weigh two pounds! Think of the slime trail!

These giant African land snails (Achatina fulica) are illegal in many countries including the US, but it appears some have gotten in. The snails are sometimes used in a traditional African religious ceremony where practitioners ingest their slimy gastropod juices (goodness gracious!) and word is that a woman from Africa may have smuggled them through customs under her dress in 2010. Okay.

Like many invertebrates, giant snails are hermaphroditic, possessing both male and female reproductive organs. After mating each partner can produce offspring, as many as 200 at a time, and up to 1200 a year! These things are worse than rabbits… and as big as rabbits, too.

Look at the photo again. Whoa!

Two sisters in a residential neighborhood in Miami-Dade County discovered some of the snails in their yard and showed one to a fruit fly inspector who then alerted officials at Florida’s Department of Agriculture. The agency didn’t want to bother the armed forces so they canvassed about a square mile surrounding the sisters’ house on their own and hand removed all the giant African land snails they could find. A few days later they scoured the area again and found even more.

The problem with this particular species of giant snail is that it likes to eat about 500 different types of plants, and can sometimes carry a strain of non-fatal meningitis that’s contagious to humans through contact with the gastropod (like drinking its juices – duh), so eradication of A. fulica is deemed a high priority.

This isn’t the first time Florida has been invaded by giant African land snails. In 1966, the state spent about a million bucks getting rid of 18,000 of them.

SOURCES and LINKS
Story on abcnews.com
Miami Herald story
Online News website story
More photos of giant snails
More about giant African land snails

Aug
22
2011

Happy, happy, joy, joy!: A new study touts the positive effects of Personal Activity Interventions (PAIs).
Happy, happy, joy, joy!: A new study touts the positive effects of Personal Activity Interventions (PAIs).Courtesy Mark Ryan

"Got no checkbooks, got no banks,
Still, I'd like to express my thanks.
I've got the sun in the morning
And the moon at night.“

Words and music by Irving Berlin

The simple sentiments found in the lyrics of Irving Berlin’s “I’ve Got the Sun in the Morning and the Moon at Night” are at the core of a self-administered therapy technique that has proven helpful for folks who suffer from depression.

Researchers from the University of California-Riverside and Duke University in North Carolina recently reviewed medical literature regarding a technique known as Personal Activity Interventions (PAIs). PAIs involve using simple, self-administered techniques such as counting your blessings, acting kindly towards others, showing gratitude (i.e. writing thank you notes), and meditating positive feelings about others, among other things, and according to the study, showed significant positive results for people suffering from depression. The affliction can be disabilitating, and there are a lot of sufferers out there, something like 100 million people worldwide.

Depression, according the study, is “a heterogeneous condition with molecular and biochemical origins that are still not fully understood.” It goes on to say that the World Health Organization (WHO) estimates that less than 10 percent of those who do suffer get treated for it. The reasons for lack of proper treatment range from economic distress to stigma to the lack of medical resources and providers. When resources are at hand, conventional treatments usually involve patients talking with a therapist or taking pharmaceuticals, or both. But the authors note that the current drug therapy is not quite up to par.

"Response rates to a single antidepressant are generally considered to be 60%–70%, with over 80% of the drug effect accounted for by placebo effects. Even with this relatively high percentage of ‘‘responders’’ to drug treatment, initial pharmacotherapy produces remission in only 30%– 40% of the depressed population.“

Harnessing the Power of Positive Thoughts and Emotions to Treat Depression

This brings to mind how some new television commercials are touting taking an additional drug that may be helpful if your regular anti-depressant isn’t quite doing its job. They urge you to ask your doctor if the advertised drug is right for you. So, essentially what the drug companies are saying is if one of our drugs isn’t doing it for you, just take more. What happens when the new drug doesn’t work? I think you’re asking for trouble going down that road.

But I like this idea of using PAIs. The study claims the improvement rate from their use is remarkable and longer lasting than traditional talk and drug therapies. What’s particularly interesting is that PAIs carry almost none of the obstacles involved with conventional treatment methods. Often when a patient is in the depths of depression it can be difficult for them to find the motivation to seek out traditional therapies. The steps involved in finding a therapist, setting up an appointment, getting themselves to the therapist’s office, can appear daunting when struggling with depression. Many current anti-depressants can take weeks to become effective, or can produce unwanted side effects, or even carry a stigma of embarrassment for some patients. As mentioned before, the lack of economic resources or treatment accessibility can also block a patient from getting treatment. But doing Personal Activity Interventions involve none of those obstacles, and since PAIs are self-administered, any successful results can empower a user and bolster his or hers self-esteem. The method can also give an additional sense of accomplishment because the therapy doesn’t involve the aid of outside factors such as therapists and drugs. The resulting elevated mood can raise productivity and creativity levels, and enhance personal relationships.

So, empirically, PAIs seem to be effective in reversing a downward mood spiral. I figure anything that proves helpful in battling depression can’t be bad, and that includes traditional talk and drug therapies. It’s interesting to note that besides in Irving Berlin’s song some of the techniques found in the PAIs method such as expressing gratitude, wishing others well, and meditating can also be found in many 12-step recovery programs, such as Alcoholics Anonymous.

The review appeared in the Journal of Alternative and Complementary Medicine and is available free online to download here.

Eurekalert
More about depression