Phones, tablets, and PCs can play online video on a TV set using Google’s cheap Chromecast device.

Google launched a two-inch-long device costing $35 at an event in San Francisco today. The device is meant to bring the 200 billion videos watched online each month to regular TV sets. Called the Chromecast, the device resembles a regular USB thumb drive, but plugs into a television’s HDMI port and connects to a home Wi-Fi connection.

UMBC is pleased to announce the appointment of Dr. Zeev Rosenzweig as chair of the department of chemistry and biochemistry and professor of chemistry, effective January 1, 2014.

Rosenzweig will come to UMBC from the National Science Foundation, where he is presently a program director in the division of chemistry. He also carries the title of professor adjunct in the chemistry department of the University of New Orleans, where he was previously a professor. His research interests are in the synthesis of nanomaterials and their applications in biological and environmental systems.

“We are delighted to have Dr. Rosenzweig be a member of our campus. He is a gifted and talented researcher, experienced educator, and proven administrator,” said William LaCourse, dean of the college of natural and mathematical sciences.

In addition to his management and leadership experience, Rosenzweig has an outstanding record of scholarship. He received his B.Sc. in Chemistry in 1986 and Ph.D. in Physical Chemistry from The Hebrew University of Jerusalem in 1992. He also held postdoctoral research positions at the Ames Laboratory of Iowa State University (mentored by Dr. Edward S. Yeung) and the University of Michigan (mentored by Dr. Raoul Kopelman). He is the author of 57 refereed papers in a variety of prestigious journals, eight book chapters and one patent. Rosenzweig has presented numerous papers at national and international conferences. Rosenzweig’s leadership and excellence has been recognized with an NSF CAREER award, Hebrew University Visiting Scholar Award, and a number of service awards from NSF including the NSF Director’s Superior Accomplishment Award.

On accepting his appointment as the chemistry and biochemistry chair, Rosenzweig said, “I am honored to have been selected Chair of the Department of Chemistry and Biochemistry at UMBC. I thank Dean LaCourse and the search committee for their confidence in me to work with the faculty and lead the department to continued excellence in chemistry and biochemistry research, teaching, and service in the upcoming years. I am excited about the opportunity to redevelop my research program in the area of nanomaterials chemistry and to make significant contributions to solving sustainability and human health problems through the use of nanoscience and nanotechnology. I wish to thank NSF for providing me with the opportunity to serve the community as Program Director in the Division of Chemistry for the last eight years. I believe that lessons I learned from my NSF experience will prove invaluable as I assume my new role as Department Chair. Finally, I wish to thank the outgoing Department Chair Dr. Richard Karpel for his leadership over the past few years, which has allowed the UMBC Chemistry Department to maintain its tradition of excellence.”

Rosenzweig’s appointment as chair brings to a conclusion a successful national search for a leader who will build upon, and enhance, the outstanding reputation of UMBC’s department of chemistry and biochemistry in teaching, research, outreach and service.

Pagination over a constantly changing list is hard. Really hard. In fact it should be one of those computer science problems up there with naming and cache invalidation.

The issue especially surfaces in news sites, like Hacker News. The hierarchy of posts is constantly changing. By the time you click ‘next page’, page two has an entirely different set of posts. So how do you ensure that the next page contains what the user expects to see?

Paginating on offset is out, since the valid offset is constantly changing. Paginating on a post’s date is also out, since HN’s sort order is not determined by date, but rather by a dynamic score.

Well one one method is to store every possible sort order in memory. In fact, this is exactly what Hacker News does. When you click ‘next page’, HN knows what you’re expecting to see, because it has the particular sort order you’re looking at stored in a closure.

However this is a lot of data. And it only grows. This means that every so often the garbage collector comes through and expires old links. And old can mean a couple of minutes - far too quick for practical pagination in my opinion.

@fat came up with a neat solution for Medium, which he shared with me recently. In fact the solution is so simple that I nearly kicked myself.

Send the server the IDs of the posts you already have when paginating. Sort posts by score, limit to your pagination offset, and omit those supplied IDs from the returned collection.

In other words I send an array containing all the previously fetched post IDs as a parameter whenever I’m fetching more paginated posts. Then I make sure that any posts fetched from the DB aren’t referenced in those IDs.

That’s a pretty pragmatic solution, that in my opinion draws the right compromises. Since I’m paginating via infinite scrolling, rather than links, users won’t notice ugly post IDs in the URLs. And since I’m keeping the list current using a stream of realtime updates from the server, posts are unlikely to be out of order. All in all, I’m pretty happy with the approach.