Monday, December 22, 2008
This is expressed most clearly in Mr. Obama's own words:
"...the truth is that promoting science isn’t just about providing resources—it’s about protecting free and open inquiry. It’s about ensuring that facts and evidence are never twisted or obscured by politics or ideology. It’s about listening to what our scientists have to say, even when it’s inconvenient—especially when it’s inconvenient. Because the highest purpose of science is the search for knowledge, truth and a greater understanding of the world around us."
From the Science Team Rollout Radio Address
Listen to the NPR Story.
And to that I say, Amen.
Wednesday, December 10, 2008
LOE's Bruce Gellerman interviews John Mussa, a reporter with Internews in southern Sudan. Read the transcript or download the MP3 version, and you'll no longer take your local radio station for granted!
After War, Wind-Powered Radio
"Twenty-two years of civil war destroyed Sudan’s electrical infrastructure, so locals have turned to wind and solar energy to power their new radio station."
Friday, December 05, 2008
- Heifer International.
- NRDC Great Green Gift Guide.
- Oxfam America Unwrapped.
- Ten Thousand Villages. (some products are carried locally at Ben Franklin!)
- TreeHugger Holiday Gift Guide.
- World of Good from eBay.
- Yahoo Green Gift Guide.
If you know of other great sources for sustainable, fair trade, and/or locally produced gifts, don't hesitate to add your comments. Thanks!
Thursday, December 04, 2008
Entropy and evolution. American Journal of Physics, Volume 76, issue 11 (November 2008), p. 1031-1033
Author's abstract: Quantitative estimates of the entropy involved in biological evolution demonstrate that there is no conflict between evolution and the second law of thermodynamics. The calculations are elementary and could be used to enliven the thermodynamics portion of a high school or introductory college physics course.
The article is accessible to all OhioLINK affiliates at the OhioLINK Electronic Journal Center.
Interested in seeing current articles from other Oberlin science faculty? ISI Web of Science (also known as Science Citation Index) provides a quick way to search across all science disiciplines. Search "Oberlin Coll" as an address phrase, limit to 2008, and you'll find 40 papers in seconds.
Wednesday, December 03, 2008
Learn more about science education at Oberlin at the College Archives, beginning with the very worthy Dr. James Dascomb, village and college physician, chemistry, botany and physiology professor, and, briefly, college librarian. Dr. Dascomb also taught sacred music, rhetoric, mathematics and civil law, among other courses, according to the 1836 Catalogue. This photo, courtesy of the Oberlin College Archives, was taken in the 1850s. The Archives department is a wonderful place to research our past.
The Oberlin Alumni Magazine for December 1961 includes a nice history of science education at Oberlin. It's available in the Archives or in the periodical stacks on the 2nd floor of the Main Library.
Tuesday, December 02, 2008
Monday, December 01, 2008
One of the highlighted articles considers polar bears and climate change, a very timely topic given the Defenders of Wildlife new report on the urgent need to act now to protect wildlife from global warming.
Read your way through the Web site and you'll be wonderfully informed on the most pressing issues in bioscience today - and better prepared to appreciate the Year of Science, to be celebrated in 2009.
Wednesday, November 19, 2008
What's That Stuff? considers contact lens solutions this week. Have you stopped to wonder what's pooling around that contact lens as you tease it out of its lens case? Or given any thought to be benefits of the moisturizing agent polyvinyl pyrrolidone as opposed to, say, your own spit? No? You might want to find out!
Tuesday, November 18, 2008
- Mean and lowly things by Kate Jackson, is a naturalist's glaringly truthful account of snakes, science, and survival in the Congo.
- A Supremely bad idea by Luke Dempsey follows three mad birders and their quest to see it all through 8 states, 1 foreign country, 129 towns, 34 national parks and "too many alarming motel rooms" to chase the most beautiful and rarest birds the country offers. [Listen to Bruce Gellerman's interview with the author on Living on Earth, Sept. 12]
- David and Richard Garfinkle's Three steps to the universe offers a guided tour from the sun to black holes to the mystery of dark matter throughout the entire universe.
- What the nose knows (Avery Gilbert) explores the science of scent in everyday life. One could only wish for scratch and sniff cards to make it complete.
- Peter Pringle brings us the story of Stalin's persecution of one of the great scientists of the twentieth century, in The Murder of Nikolai Vavilov.
Thursday, November 13, 2008
On the weekend of November 15–16, 2008, the American Chemical Society Publications website will be unavailable as they deploy a dynamic new web delivery platform, hosting all 34 ACS Journals on a platform rich with new features and functionality. A flash-based demo showcasing many of the features and benefits of the new site is available at: http://pubs.acs.org/flashdemo
Download what you need before 8:30 a.m. Saturday!
Tuesday, October 21, 2008
For National Security, Get Off Oil
Former CIA director R. James Woolsey says America's oil dependence is a grave threat
By Stephen D. Solomon
"At R. James Woolsey’s farm in southern Maryland, solar panels on the roof of his house send electricity back to the utility grid when his family is not using much power. And he drives a Toyota Prius hybrid with a conversion kit that enables him to recharge the car’s battery pack using an extension cord and household current."
Read more at Scientific American online
SciAm.com > Special Editions > Energy > Automotive Technology
Interested in learning more about hybrid cars and other energy technologies, from a physics perspective? Here's a fascinating new book that has just been cataloged on OBIS: Physics of societal issues : calculations on national security, environment, and energy / David Hafemeister. New York : Springer, c2007
Available online to OhioLINK libraries at springerlink.com. Link there from OBIS.
Tuesday, October 14, 2008
JSTOR continues to expand in the number of journal titles archived and in the wonderful flexibility of its search features. It also provides an easy way to jump from the archive to more recent issues of any journal title, through links to publishers' web sites and the OhioLINK Electronic Journal Center when appropriate.
BROWSE BY DISCIPLINE is a quick way to see all of the content in a broadly defined subject area. The biological sciences are well-represented in JSTOR, but physical and chemical studies are plentiful in the General Science category. See, for example:
Philosophical Transactions: Mathematical, Physical and Engineering Sciences Vol. 358, No. 1766, Jan., 2000
Science into the Next Millenium: Young Scientists Give Their Visions of the Future: II: Chemistry and Biological Physics.
Science titles added to the JSTOR archives in the past few months include:
American Biology Teacher
Create a MyJSTOR account, and you can take advantage of some great new features, such as exporting saved citations directly to RefWorks.
Monday, October 13, 2008
Monday, September 08, 2008
- Encyclopedia of Scientific Principles, Laws, and Theories / Robert E. Krebs. 2 vols.
- The Senses: a Comprehensive Reference / Stuart Firestein, et al., editors. 6 vols.
The Senses is far more in-depth in its presentation, providing longer articles on very specific topics (Neurotransmitters in the taste pathway; Aquatic animal models in the study of chemoreception; and Genomics of invertebrate olfaction are just three articles out of 220 or so). Each article is supported by numerous references to primary literature, so this is a very good starting point for research. Good illustrations and photographs add to its usefulness.
There are many other enticing books on the new book shelf - stop by and enjoy looking at the book covers and reading blurbs, at least, in between class and lab.
Monday, September 01, 2008
Explore the basics of permaculture, a system of design that uses principles and processes found in nature to create food, fuel, and fiber for people, while caring for the earth and its inhabitants.
Focus on edible forest gardens; gardens which look and function like forests and provide food for people in urban and rural homes alike. From the design through planting and care, expert designers Josh Beniston of Habitats Landscaping and Brett Joseph of Conneaut Creek Farm will tell how to create such a garden anywhere.
$45 OEFFA members/ $60 non-members. Class size is limited so sign up early! Please bring your own brown bag lunch.
To register, send your check, along with your name, address, phone number and email to: OEFFA Workshops, 41 Croswell Road, Columbus OH 43214. Questions can be directed to firstname.lastname@example.org or 614-421-2022.
Cleveland Museum of Natural History, Classroom A
1 Wade Oval Drive, University Circle, Cleveland OH 44106-1767
Saturday, Sept 20 - 9am-5pm
Tuesday, August 26, 2008
Science library tours are Friday afternoon @ 1:00, 1:30, 2:00 and 2:30. Only 20 minutes in length! You'll get to practice using the movable, compact shelving, find the current issue of Nature, check out a good study carrel to claim for the semester, and take a post-tour nap in a window seat, if you're so inclined. Nappers always welcome. See you Friday!
Friday, August 15, 2008
Tuesday, July 29, 2008
I came across this photo while sorting through a drawer recently, and felt nostalgic at the sight of so many print journal issues! Just look at all those lovely things. The biology section of the current journals area is practically overflowing. This was taken early in the summer of 2002, after our first academic year in the new Science Center, and we were apparently gathering journals for binding (note the stacks of issues lying on top of the low shelving). Within just a few months more than 70 of these print titles were cancelled, in favor of online-only access at the OhioLINK Electronic Journal Center, and we have continued to reduce the print collection since then. How quickly things can change!
Tuesday, July 22, 2008
S. A. FitzGerald, K. Allen, P. Landerman, J. Hopkins, J. Matters, R. Myers, and J. L. C. Rowsell, "Quantum Dynamics of Adsorbed H2 in the Microporous Framework MOF-5 Analyzed using Diffuse Reflectance Infrared Spectroscopy"
Physical Review B 77, 224301 (2008).
Thanks to Jesse Rowsell for providing this information: "Employing hydrogen as an energy carrier continues to be a lofty goal, with significant technological challenges remaining unmet. Storing the supercritical gas, both safely and efficiently, is a particularly difficult endeavour for vehicular power generation, i.e. using fuel cells. To improve hydrogen storage densities, several classes of sorbent materials have been identified. Only a handful of analytical tools are currently available to assist scientists in understanding the interaction between H2 and these materials, some requiring very expensive instrumentation and limited resources, such as nuclear reactors.
"Our work involves the use of a compact infrared spectrometer equipped with a sample chamber that can be pressurized with hydrogen gas and cooled to temperatures approaching 10 K (-263°C). Under these conditions, hydrogen molecules stick to the surface of the sorbent material and their rotational and vibrational motion--which is quantum mechanical--can be analyzed. Ultimately, the spectral data provide information on the strength of the H2 binding at discrete sites on the material's surface, allowing an assessment of its performance. As we analyze a wider array of sorbents, correlations between their structures and properties should emerge, providing some direction for enhancing their hydrogen storage efficiencies."
Jesse Hopkis 2009
Patrick Landreman 2008
John Matters 2008
Kelty Allen 2007
Ross Myers 2007
Wednesday, July 16, 2008
Farm Fuel Inc. is also involved in developing biodiesel for transit buses. Scott Doggett, a contributor to Green Car Advisor, tells more in his post "This Biodiesel Plan's a Spicy One!"
Thursday, July 03, 2008
The July issue of GSA Today, published for members of the Geological Society of America (GSA), includes an indepth study of the geological and geophysical factors of the recent deadly earthquake in China.
Given the world-wide interest in this devastating event, the GSA has made the article available for open access.
Tuesday, June 24, 2008
Monday, June 23, 2008
The Mystery of the Missing Antimatter "is at once a history of ideas and an exploration of modern science and the frontiers of human knowledge" [from the publisher, Princeton Univ. Press].
There are dozens more on the new book list! Selected keywords from the list will whet your appetite for good reading: Archimedes, Hiroshima, stem cell ethics, feminist science, DNA & evolution, nanosilicon, death in the Cretaceous, seashells, parasitoids, sexual behavior, synergy, biomass combustion, hydrogen future, neuroeconomics, Amazon, stream ecology...
stop in and check out a few. Heard of a good book we should order? Tell us! email aricker at oberlin.edu. Thanks.
Friday, May 30, 2008
As reported by Andrew C. Revkin in the New York Times (May 28, 2008, p. A14), "The rise in concentrations of carbon dioxide in the atmosphere from human activities is influencing climate patterns and vegetation across the United States and will significantly disrupt water supplies, agriculture, forestry and ecosystems for decades." Among the more sobering conclusions of the report are the predictions of wide-spread water shortages in the western U.S., with dire consequences for populations and agriculture, and the migration of invasive species adversely impacting ecosystems throughout North America.
Healthy biodiversity, essential for ecosystem maintenance, is predicted to suffer as species struggle to adapt to rising temperatures, and conditions that encourage parasitic-induced disease as well as competition for resources and suitable reproductive habitats. From the Executive Summary: "The resilience of many ecosystems is likely to be exceeded this century by an unprecedented combination of climate change, associated disturbances (e.g., flooding, drought, wildfire, insects, ocean acidification), and other global change drivers (e.g., land use change, pollution)." Read the Summary and Findings.
Friday, May 16, 2008
"Fitness effects of mutation accumulation in a natural outbred population of wild radish (Raphanus raphanistrum): comparison of field and greenhouse environments."
vol. 62 (May): 1066-1075.
This issue was not yet accessible on either the BioOne or OhioLINK EJC servers at the time of this posting, but it will be very soon. In the meantime, you can read the print issue in the library.
Wednesday, May 14, 2008
Despite listing polar bear as a species requiring protection under the Endangered Species Act, the first such listing attributed to loss of habitat due to global warming, Interior Secretary Dirk Kempthorne said it would be "inappropriate" to use the listing as an impetus to address global warming generally or reduction of greenhouse gases specifically. Learn more at Defenders of Wildlife.
Friday, May 09, 2008
"Frogs, salamanders and other amphibians are on a slippery path to extinction. Habitat loss, disease, global warming and other factors are taking their toll. Worldwide, a third of these key players in the web of life are considered threatened -- making amphibians the most vulnerable group of animals in the world.
"This month, Defenders Magazine profiles the plight of these slick critters -- and takes a look at what people are doing to save them."
Learn more about amphibians in this recent book in our reference collection:
The ecology & behavior of amphibians / Kentwood D. Wells
Tuesday, May 06, 2008
Please read our revised lending policy for the laptop loaners, available to students, faculty and staff with current and valid OCID.
Highlights: iBook G4s may go out overnight - but must be back by 10am the next day (Mon-Fri) or by 1pm the next day if borrowed on Friday or Saturday afternoon. There is now a penalty fee of $20 (ouch!) for unauthorized overnight use, so PLEASE pay attention to the due time and our closing times!
Monday, May 05, 2008
Visit the site:
Global Warming: It’s All About Carbon, Cartoon Series Main Page
Friday, May 02, 2008
Tune into NPR.org for yesterday's story on Oberlin's Fearless campaign. It's interesting listening, and Dan Bobkoff of member station WCPN in Cleveland does a good job of presenting different points of view.
All Things Considered, May 1, 2008 · A top-notch Ohio college's two-year-old marketing campaign — "We Are Oberlin: Fearless" — is the subject of internal mockery from Oberlin students.
Thanks to Kolleen for sharing this.
Wednesday, April 30, 2008
The Guardian (April 7, 2008) reported on Hansen's latest paper, co-published with eight others in arXiv, on appropriate targets for levels of atmospheric carbon.
Books on animal societies and behavior are also well-represented in this latest shipment: rhesus monkeys, gorillas, turtles, rodents, hornbills, eagles, ants and lizards - oh my! There are plenty of titles to entice those of you reading chemistry, geology, physics and other aspects of biology as well.
Friday, April 25, 2008
*How similar are we to those other species? I'm glad you asked! Here's the answer I received to that question on genome.gov:
Mary Schueler, Ph.D. : Generally, human DNA is most similar to more closely related species like the great apes - chimp, gorilla, and orangutan. These are more closely related to us in evolutionary time. Species that have been separated from us for longer periods of time share less similarity. As you compare with species farther away from us on the evolutionary tree, we observe that DNA sequences that code for proteins are conserved while other sequence is not. This is thought to be due to the necessary function of the proteins in the life of the cell. If the sequence changes, the cell can't survive. We are less than 90% similar to most other species. Even within the primate lineage, as compared to old world monkeys, protein coding sequences can vary by as much as 15% (be 85% similar). As you move further away to mice and flies and yeast, the percentage similarity falls off quite a bit.
Tuesday, April 22, 2008
Lie on the grass.
Breathe in the scent of magnolias.
Love the earth.
Take a book out with you!
A few suggestions:
- Beyond Earth Day. Main Library GE195.N45 2002
- Earth: the sequel. Science Library TJ163.4.U6 K78 2008
- Humanity's Footprint. Main Library GF75.D65 2008
Friday, April 18, 2008
- The technology that will save humanity "The solar energy you haven't heard of is the one best suited to generate clean electricity for generations to come." By Joseph Romm. Salon.com April 13, 2008
- A Renewed Push for Ethanol, Without the Coal. New York Times, April 17, 2007
- Cellulosic Ethanol - Renewable Fuels Association
- Wind Industry and Projects for Ohio Richard Stuebi, BP Fellow for Energy and Environmental Advancement
- Midwest Regional Carbon Sequestration Partnership (on DOE Web site) and MRCSP.org
- The Wedge Stabilization model - supported by Dow Chemical, as outlined by Princeton Professors Socolow and Pacala in their article, "A Plan to Keep Carbon in Check", which appeared in the September 2006 issue of Scientific American.
- Solar Design Associates
Wednesday, April 16, 2008
Also check out A Science Fair for a Better Planet: "A contest to show Discover—and the rest of the humans—how to help Mother Earth". You can enter your own ideas in what is being billed as the World's biggest Show and Tell.
Tuesday, April 15, 2008
Tuesday, April 08, 2008
"Shall not geology, which is the first science in affording scope for the imagination, be brought into favor with the Muses, and afford themes for the Poet?"
—Edward Hitchcock, Jr., 1849
You would surely enjoy the The Biochemist's Songbook (take to your next fireside sing-along and amaze your friends with references to complex biochemical pathways).
FirstScience.com offers an entire section on poetry.
The poetry collection in the main library is brimming with science-themed compositions - go explore books with call numbers that begin PS3551, for starters. You can spend a life-time there.
Submit your own science poetry here! Just leave a comment with your creative lines. We'll post your submissions in the science library at the end of April. An award (very modest, possibly edible) might be in the offing!
Wednesday, April 02, 2008
From the EBSCO press release:
GreenFILE offers a unique perspective on the positive and negative ways humans affect the ecology. The initial release will include abstracting and indexing for more than 600 titles, including comprehensive coverage – from to volume 1, issue 1 to present – for Bioscience (back to 1964), Conservation Biology (back to 1987), Journal of Ecology (back to 1913) and Journal of Environmental Planning & Management (back to 1948). The total number of records is approximately 295,000, and full text is provided for more than 4,600 records from open access titles.
See the list of DVDs owned by the Science Library [pdf].
Monday, March 31, 2008
Stop by the library for a look at some related reading now on display in the front window. Although this book and other closely related titles are currently checked out from Oberlin's library, you can find other copies available through OhioLINK.
Downtown bookstores offer copies of Zatorre's work, along with two other fascinating books for the general reader : Daniel Levitin's This is Your Brain on Music and Musicophilia: tales of music and the brain, by Oliver Sacks.
Read a chapter or two, even if you think you don't have time - it's good for the brain! Possibly even better if you take a break and sing or play an instrument in between chapters...
Thursday, March 20, 2008
Tuesday, March 18, 2008
Read reviews of published volumes from various journals archived in the OhioLINK Electronic Journal Center. Wikipedia provides a very nice overview of the set, complete with all contents of volumes published to date. The most recently received volumes are on display with the new books, others are in the reference section.
Image taken from the jacket cover of vol. 8: Broadbills to Tapaculos, illustrated by Frances Jutglar. Black-and-red Broadbill (Cymbirhynchus macrorhynchos).
Friday, March 14, 2008
Thursday, March 13, 2008
Thanks to Dr. John C. Abbot, Curator of Entomology, Texas Natural Science Center of University of Texas, Austin, for making such a fine and reliable source of information openly accessible, and to all contributors of OdonataCentral for building the database. John Abbott is author of Dragonflies and Damselflies of Texas and South-Central United States, which you can borrow through OhioLINK.
Monday, February 18, 2008
Under a Green Sky - Global Warming, Mass Extinctions of the Past and What They Can Tell Us About the Future.
Here is a snippet from the Booklist review:
"Paleontologist and science writer Ward combines tales of his own punishing fieldwork with a piquant history of the controversies that have dogged scientists seeking the cause of the "mother of all extinctions" in the Permian period. This provides the foundation for a stunning discovery: evidence of past greenhouse extinctions. As Ward carefully parses the data and its implications, he observes, 'the key to climate change seems to be both the level and the rate at which carbon dioxide rises in the atmosphere,' no matter its source."
The library owns several other books by Ward, equally useful for understanding the relationship between global climate and biodiversity.
Thursday, February 14, 2008
Jackie Savitz, Pollution Campaign Director, Senior Scientist, Oceana
Carl Safina, founder of the Blue Ocean Institute, adjunct professor at the School of Marine and Atmospheric Sciences at Stony Brook University, and author of "Voyage of the Sea Turtle," "Song for the Blue Ocean," and other books [search OhioLINK catalog by author].
Dr. Dariush Mozaffarian, cardiologist and epidemiologist at the Harvard School of Public Health.
Tuesday, February 12, 2008
CHARLES ROBERT DARWINDarwin Day Celebration is an "international recognition of science and humanity." On this 199th anniversary of Darwin's birth, take a few moments to marvel over the amazing interactions of genetics, habitat, adaptation, predation, mutation, and exploration that led, over millennia, to the satisfying specimen of biological achievement that is you.
February 12, 1809 to April 19, 1882
We have a gazillion books and journal articles to help you learn more! Even a video or two.
Find genetics related videos from the OhioLINK Digital Video Collection by searching Genetics as a subject heading, limited to material type Videos. Genetics & Evolution, from Films for the Humanities & Sciences, summarizes the theory of natural selection and describes the process of trait inheritance.
Wonderful books about Charles Darwin await your reading pleasure in the library. Browse just a few of them now on display at the science library circulation desk, along with selected other titles on evolution, biological diversity, and genetics.
An online course on Evolution, Creationism, and the Nature of Science,
Online Course: Evolution, Creationism and the Nature of Science
Monday, February 11, 2008
The bottom left corner of C&EN's home page offers a number of special features, including C&EN blogs, Critter Chemistry, Green Chemistry, and Climate Change. The last three are collections of articles and news specific to those subjects. Enjoy reading this weekly news magazine from ACS.
Tuesday, February 05, 2008
Monday, February 04, 2008
The transmission over NASA's Deep Space Network will commemorate the 40th anniversary of the day The Beatles recorded the song, as well as the 50th anniversary of NASA's founding and the group's beginnings. Two other anniversaries also are being honored: The launch 50 years ago this week of Explorer 1, the first U.S. satellite, and the founding 45 years ago of the Deep Space Network, an international network of antennas that supports missions to explore the universe.
As part of the celebration, the public around the world has been invited to participate in the event by simultaneously playing the song at the same time it is transmitted by NASA. Many of the senior NASA scientists and engineers involved in the effort are among the group's biggest fans.
Wednesday, January 16, 2008
From the Ohio fact sheet: "Rising temperatures and drops in lake levels in the state will likely change the makeup of entire ecosystems, forcing wildlife to shift their ranges or adapt." Each fact sheet includes solutions for global warming that are specific for the state or region.
Thursday, January 10, 2008
Philica is an online, open-access journal accepting manuscripts in any discipline. It describes itself as "instant academic publishing with transparent peer-review" and currently features 121 articles and observations. Submitted papers span the humanities, social sciences and natural sciences, with greater numbers of articles in astronomy, physics, biology and chemistry. Music, philosophy, political studies, anthropology, and history are just some of the other disciplines represented, so it is truly multidisciplinary.
Learn more at the Philica site, taking special note of the essay "What's the problem with academic publishing?" and the list of articles needing review. You may find a paper that you are uniquely qualified to review, and are invited to do so. To write a review, simply click the link at the bottom of the article or observation.
Wednesday, January 09, 2008
In "Cryptochromes Define a Novel Circadian Clock Mechanism in Monarch Butterflies That May Underlie Sun Compass Navigation," published in PLoS Biology, Steven Reppert and colleagues reveal that the circadian clock of the monarch uses a novel molecular mechanism, heretofore not found in any other insect or mammal."
Read the story by the Associated Press in Google news as well as Walton's blog entry and papers in PLoS.
Friday, January 04, 2008
The Science news article illustrates Barack's support for science policy and research based on factual, peer-reviewed evidence:
"Deborah Burnet, a pediatrician at the University of Chicago who studies the connection between obesity and diabetes, says Obama displayed the same evidence-based philosophy whenever she invited the Harvard Law School grad and community organizer to lecture her class on racial disparities in health. The 30-something Obama would urge her students to think about "how to use scientific inquiry to make intelligent public policy," says Burnet."
Read the full story (DOI: 10.1126/science.319.5859.28a). For on-campus users or your Oberlin login required.
Wednesday, January 02, 2008
Check out the entire list, from antibiotic resistant infections, California wildfires and James Watson to the disappearance of the Yangtze River Dolphin.
Sign up for Scientific American e-newsletters.