Dynamic view of city created based on Foursquare check-in data

ScienceDaily (May 1, 2012) — The millions of "check-ins" generated by foursquare, the location-based social networking site, can be used to create a dynamic view of a city's workings and character, Carnegie Mellon University researchers say. In contrast to static neighborhood boundaries and dated census figures, these "Livehoods" reflect the ever-changing patterns of city life.

Researchers from the School of Computer Science (SCS) have developed an algorithm that takes the check-ins generated when foursquare members visit participating businesses or venues, and clusters them based on a combination of the location of the venues and the groups of people who most often visit them. This information is then mapped to reveal a city's Livehoods, a term coined by the SCS researchers.

Maps for New York, San Francisco and Pittsburgh are available on the project website, http://livehoods.org/. People can help choose the next city to map by voting on the Livehoods Facebook page.

"Our goal is to understand how cities work through the lens of social media," said Justin Cranshaw, a Ph.D. student in SCS's Institute for Software Research.

Part of the emerging field of Urban Computing, the Livehoods project takes advantage of the proliferation of smartphones and the location-based services they make possible. In this case, the researchers analyzed data from foursquare, but the same computational techniques could be applied to many location-based databases.

Livehoods thus provide a powerful new tool that could be used to address a wide variety of urban problems and opportunities. The researchers are exploring applications to city planning, transportation and real estate development. Livehoods also could be useful for businesses developing marketing campaigns or for public health officials tracking the spread of disease.

"In urban studies, researchers have always had to interview lots of people to get a sense of a community's character and, even then, they must extrapolate from only a small sample of the community," said Raz Schwartz, a Ph.D. student at Bar-Ilan University, Israel, and a visiting scholar at SCS's Human-Computer Interaction Institute. "Now, by using foursquare data, we're able to tap a large database that can be continually updated."

The Livehoods project is led by Norman Sadeh, professor and co-director of the Institute for Software Research's Ph.D. program in Computation, Organizations and Society, and Jason Hong, associate professor in the Human-Computer Interaction Institute. The team will present its findings June 5 at the International AAAI Conference on Weblogs and Social Media (ICWSM) in Dublin, Ireland.

All of the Livehoods analysis is based on foursquare check-ins that users have shared publicly via social networks such as Twitter. This dataset of 18 million check-ins includes user ID, time, latitude and longitude, and the name and category of the venue for each check-in.

In their study of the Pittsburgh metropolitan area, the researchers found that the Livehoods they identified sometimes spilled over existing neighborhood boundaries, or identified several communities within a neighborhood. The Pittsburgh analysis was based on 42,787 check-ins by 3,840 users at 5,349 venues.

For instance, they found that the upscale neighborhood of Shadyside actually had two demographically distinct Livehoods -- an older, staid community to the west and a younger, "indie" community to the east. Moreover, the younger Livehood spilled over into East Liberty, a neighborhood that long suffered from decay but recently has seen some upscale development.

"That makes sense to me," observed a 24-year-old resident of eastern Shadyside, one of 27 Pittsburgh residents who were interviewed by researchers to validate the findings. "I think at one point it was more walled off and this was poor (East Liberty) and this was wealthy (Shadyside) and now there are nice places in East Liberty and there's some more diversity in this area (eastern Shadyside)."

The researchers found that one Pittsburgh neighborhood, the South Side Flats, contained four distinct Livehoods, including one centered on bars popular with college students, another centered on a new shopping district dominated by chain stores and another that focused on a supermarket. Again, these Livehoods made sense to residents familiar with the area.

The study has limitations. Foursquare users tend to be young, urban professionals with smartphones. Consequently, areas of cities with older, poorer populations are nearly blank in the Livehoods maps. "You can literally see the digital divide," Schwartz said. Likewise, foursquare members don't check-in at all of their destinations -- hospitals, for instance. But the researchers contend that the limitations are those of the data, not the methodology.

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It's the network: Ever wonder why your friends have more friends than you or diamond is harder than graphite?

ScienceDaily (Apr. 19, 2012) — A new article by a Northwestern University complex networks expert discusses how networks governing processes in nature and society are becoming increasingly amenable to modeling, forecast and control.

The article establishes relationships between seemingly disparate topics such as the friendship paradox -- by which our friends have on average more friends than we do -- and why carbon can result in a hard diamond or the softer material graphite.

"Many broadly significant scientific questions, ranging from self-organization and information flow to systemic robustness, can now be properly formalized within the emerging theory of networks," said Adilson E. Motter, the Harold H. and Virginia Anderson Professor of Physics and Astronomy at Northwestern's Weinberg College of Arts and Sciences. "I was thus humbled to be invited to write such a timely piece."

Motter is first author of the article "Networks in Motion," published last week as the cover story in Physics Today, the membership journal of the American Institute of Physics. His co-author is Réka Albert, professor of physics and biology at Penn State University.

The authors argue that, as network research matures, there will be increasing opportunities to exploit network concepts to also engineer new systems with desirable properties that may not be readily available in existing ones. Examples include emerging areas such as synthetic biology and microfluidics, which could be radically changed by rational circuit design, but also established areas such as traffic and materials research.

Motter and Albert consider the problem of network control, particularly in the context of biological networks as a promising new avenue for disease treatment. Cascading processes, in particular, in which successive elements in a complex network fail, are shown to be not as unstoppable as previously thought.

They also discuss at length how collective behavior may depend on properties of the underlying network, even when composed of the exact same nodes -- as in the case of radically different materials made of the same chemical element.

By and large, the recent study of complex systems has been centered on the identification and analysis of network features relevant to a particular phenomenon of interest, ultimately reducing complexity. But, the authors ask, with so many conceivable possibilities, what if one simply fails to look for the right features? Researchers have been thinking about this, too, and, as a result, exploratory methods are now being devised to identify patterns not anticipated by pre-conceptions.

One such method mentioned in the article aims at resolving the internal structure of complex networks by organizing the nodes into groups that share something in common, even if researchers do not know a priori what that thing is.

"This is, of course, only the very tip of the iceberg," Motter said. "A broader undertaking concerns the development of similar exploratory approaches that can also systematically account for network dynamics, which remains widely unexplored."

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The above story is reprinted from materials provided by Northwestern University. The original article was written by Megan Fellman.

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Journal Reference:

Adilson E. Motter, Re´ka Albert. Networks in motion. Physics Today, 2012; 65 (4): 43 DOI: 10.1063/PT.3.1518

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Internet usage patterns may signify depression

ScienceDaily (May 16, 2012) — In a new study analyzing Internet usage among college students, researchers at Missouri University of Science and Technology have found that students who show signs of depression tend to use the Internet differently than those who show no symptoms of depression.

Using actual Internet usage data collected from the university's network, the researchers identified nine fine-grained patterns of Internet usage that may indicate depression. For example, students showing signs of depression tend to use file-sharing services more than their counterparts, and also use the Internet in a more random manner, frequently switching among several applications.

The researchers' findings provide new insights on the association between Internet use and depression compared to existing studies, says Dr. Sriram Chellappan, an assistant professor of computer science at Missouri S&T and the lead researcher in the study.

"The study is believed to be the first that uses actual Internet data, collected unobtrusively and anonymously, to associate Internet usage with signs of depression," Chellappan says. Previous research on Internet usage has relied on surveys, which are "a far less accurate way" of assessing how people use the Internet, he says.

"This is because when students themselves reported their volume and type of Internet activity, the amount of Internet usage data is limited because people's memories fade with time," Chellappan says. "There may be errors and social desirability bias when students report their own Internet usage." Social desirability bias refers to the tendency of survey respondents to answer questions in a manner that will be viewed favorably by others.

Chellappan and his fellow researchers collected a month's worth of Internet data for 216 Missouri S&T undergraduate students. The data was collected anonymously and unobtrusively, and students involved in the study were assigned pseudonyms to keep their identities hidden from the researchers.

Before the researchers collected the usage data from the campus network, the students were tested to determine whether they showed signs of depression. The researchers then analyzed the usage data of the study participants. They found that students who showed signs of depression used the Internet much differently than the other study participants.

Chellappan and his colleagues found that depressed students tended to use file-sharing services, send email and chat online more than the other students. Depressed students also tended to use higher "packets per flow" applications, those high-bandwidth applications often associated with online videos and games, than their counterparts.

Students who showed signs of depression also tended to use the Internet in a more "random" manner -- frequently switching among applications, perhaps from chat rooms to games to email. Chellappan thinks that randomness may indicate trouble concentrating, a characteristic associated with depression.

The randomness stood out to Chellappan after his graduate student, Raghavendra Kotikalapudi, examined the "flow duration entropy" of students' online usage. Flow duration entropy refers to the consistency of Internet use during certain periods of time. The lower the flow duration entropy, the more consistent the Internet use.

"Students showing signs of depression had high flow duration entropy, which means that the duration of Internet flows of these students is highly inconsistent," Chellappan says.

At the beginning of the study, the 216 participating students were tested to determine whether they exhibited symptoms of depression. Based on the Center for Epidemiologic Studies-Depression (CES-D) scale, about 30 percent of the students in the study met the minimum criteria for depression. Nationally, previous studies show that between 10 percent and 40 percent of all American students suffer from depression.

To ensure that participants were not identified during the study, each participant was assigned a pseudonym. The campus information technology department then provided the on-campus Internet usage data for each participant from the month of February 2011.

The researchers' analysis of the month's worth of data led Chellappan and his colleagues to conclude that students who were identified as exhibiting symptoms of depression used the Internet differently than the other students in the study.

Chellappan's research has been accepted for publication in a forthcoming issue of IEEE Technology and Society Magazine.

The chief author of the paper is Kotikalapudi, who received his master of science degree in computer science from Missouri S&T in December 2011. His co-authors are Chellappan; Dr. Frances Montgomery, Curators' Teaching Professor of psychological science; Dr. Donald C. Wunsch, the M.K. Finley Missouri Distinguished Professor of Computer Engineering; and Karl F. Lutzen, information security officer for Missouri S&T's IT department.

Chellappan is now interested in using these findings to develop software that could be installed on home computers to help individuals determine whether their Internet usage patterns may indicate depression. The software would unobtrusively monitor Internet usage and alert individuals if their usage patterns indicate symptoms of depression.

"The software would be a cost-effective and an in-home tool that could proactively prompt users to seek medical help if their Internet usage patterns indicate possible depression," Chellappan says. "The software could also be installed on campus networks to notify counselors of students whose Internet usage patterns are indicative of depressive behavior."

Chellappan also believes the method used to connect Internet use and depression could also help diagnose other mental disorders like anorexia, bulimia, attention deficit hyperactivity disorder or schizophrenia.

"We could also investigate associations between other Internet features like visits to social networking sites, late night Internet use and randomness in time of Internet use with depressive symptoms," he says. "Applications of this study to diagnose and treat mental disorders for other vulnerable groups like the elderly and military veterans are also significant."

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Journal Reference:

Raghavendra Kotikalapudi, Sriram Chellappan, Frances Montgomery, Donald Wunsch and Karl Lutzen. Associating Depressive Symptoms in College Students with Internet Usage Using Real Internet Data. IEEE Technology and Society Magazine, 2012

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Not all today's students are 'tech-savvy'

ScienceDaily (Apr. 22, 2012) — A small minority of today's university students don't use email and others are confused by the array of technologies available at universities. Yet many students couldn't bear to be without their mobile phones and find themselves distracted by social networking sites during study.

These are the some of the findings from research funded by the Economic and Social Research Council (ESRC) into how today's generation of students use technology. The research, led by Dr Christopher Jones of the Open University, surveyed and interviewed over two thousand first year students at five English universities.

"Our research shows that the argument that there is a generational break between today's generation of young people who are immersed in new technologies and older generations who are less familiar with technology is flawed," says Dr Jones. "The diverse ways that young people use technology today shows the argument is too simplistic and that a new single generation, often called the 'net generation', with high skill levels in technology does not exist."

There was little difference in the reported IT skill levels between the sexes, except male students were more confident than female students in their use of spreadsheets, graphics, audio/video, computer maintenance and security. But university staff noted that while students had a wide exposure to technology, they often lacked an in-depth knowledge of specialised pieces of software.

The research findings included that almost all (97.8 per cent) had a mobile phone, just over three quarters (77.4 per cent) owned a laptop and over a third (38.1 per cent) owned a desktop computer. Over two thirds (70.1 per cent) felt their access to computers was sufficient to meet their computing needs, and the mobile phone was chosen by 83.2 per cent as the device students would miss most if they did not have access to it.

However, the surveys also revealed a small minority of students who either didn't use email or have access to mobile phones. For example, students who were 20 years old or younger reported being more engaged in instant messaging, texting, participating in social networks, downloading or streaming TV or video and uploading images than students who were aged 25 years or more.

In another example, only 4.3 per cent of those aged 20 or younger never used social networking websites compared to 78.5 per cent of those aged 35 years or older. The younger students also used information and communication technologies for social life and leisure more often while older students were more likely to use them for study purposes.

In their studies, students used these new technologies more than they were required to by their course. This was particularly marked for instant messaging and social networks. However, certain new technologies were only used by a minority of students regardless of their age: contributing to blogs (21.5 per cent) and wikis (12.1 per cent) or using a virtual world (2 per cent).

Despite mobile devices and broadband enabling students to study anywhere, they still inhabit the same kinds of learning spaces they used ten years ago. They continue to study in their bedrooms, the university library or other dedicated study spaces.

The distracting nature of technologies was commonly cited in the interviews but also happily accepted. Most students had developed ways to cope with the distractions while studying. These ranged from switching off the sources of distraction to taking breaks for social networking.

There was little evidence that today's students enter university with demands for new technologies that teachers and universities cannot meet. Several students reported initial surprise or confusion at the array of technologies that were available at their university, but few thought that this led to long-term difficulties. Teachers who are prepared to develop their own skills with these new technologies and integrate them carefully into their courses are unlikely to be held back by a preceding generation.

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Thwarting the cleverest attackers: Even most secure-seeming computer is shockingly vulnerable to attack

ScienceDaily (May 1, 2012) — Savvy hackers can steal a computer's secrets by timing its data storage transactions or measuring its power use. New research shows how to stop them.

In the last 10 years, cryptography researchers have demonstrated that even the most secure-seeming computer is shockingly vulnerable to attack. The time it takes a computer to store data in memory, fluctuations in its power consumption and even the noises it emits can betray information to a savvy assailant.

Attacks that use such indirect sources of information are called side-channel attacks, and the increasing popularity of cloud computing makes them an even greater threat. An attacker would have to be pretty motivated to install a device in your wall to measure your computer's power consumption. But it's comparatively easy to load a bit of code on a server in the cloud and eavesdrop on other applications it's running.

Fortunately, even as they've been researching side-channel attacks, cryptographers have also been investigating ways of stopping them. Shafi Goldwasser, the RSA Professor of Electrical Engineering and Computer Science at MIT, and her former student Guy Rothblum, who's now a researcher at Microsoft Research, recently posted a long report

on the website of the Electronic Colloquium on Computational Complexity, describing a general approach to mitigating side-channel attacks. At the Association for Computing Machinery's Symposium on Theory of Computing (STOC) in May, Goldwasser and colleagues will present a paper demonstrating how the technique she developed with Rothblum can be adapted to protect information processed on web servers.

In addition to preventing attacks on private information, Goldwasser says, the technique could also protect devices that use proprietary algorithms so that they can't be reverse-engineered by pirates or market competitors -- an application that she, Rothblum and others described at last year's AsiaCrypt conference.

Today, when a personal computer is in use, it's usually running multiple programs -- say, a word processor, a browser, a PDF viewer, maybe an email program or a spreadsheet program. All the programs are storing data in memory, but the laptop's operating system won't let any program look at the data stored by any other. The operating systems running on servers in the cloud are no different, but a malicious program could launch a side-channel attack simply by sending its own data to memory over and over again. From the time the data storage and retrieval takes, it can infer what the other programs are doing with remarkable accuracy.

Goldwasser and Rothblum's technique obscures the computational details of a program, whether it's running on a laptop or a server. Their system converts a given computation into a sequence of smaller computational modules. Data fed into the first module is encrypted, and at no point during the module's execution is it decrypted. The still-encrypted output of the first module is fed into the second module, which encrypts it in yet a different way, and so on.

The encryption schemes and the modules are devised so that the output of the final module is exactly the output of the original computation. But the operations performed by the individual modules are entirely different. A side-channel attacker could extract information about how the data in any given module is encrypted, but that won't let him deduce what the sequence of modules do as a whole. "The adversary can take measurements of each module," Goldwasser says, "but they can't learn anything more than they could from a black box."

The report by Goldwasser and Rothblum describes a type of compiler, a program that takes code written in a form intelligible to humans and converts it into the low-level instruction intelligible to a computer. There, the computational modules are an abstraction: The instruction that inaugurates a new module looks no different from the instruction that concluded the last one. But in the STOC paper, the modules are executed on different servers on a network.

According to Nigel Smart, a professor of cryptology in the computer science department at the University of Bristol in England, the danger of side-channel attacks "has been known since the late '90s."

"There's a lot of engineering that was done to try to prevent this from being a problem," Smart says, "a huge amount of engineering work. This is a megabucks industry." Much of that work, however, has relied on trial and error, Smart says. Goldwasser and Rothblum's study, on the other hand, "is a much more foundational study, looking at really foundational, deep questions about what is possible."

Moreover, Smart says, previous work on side-channel attacks tended to focus on the threat posed to handheld devices, such as cellphones and smart cards. "It would seem to me that the stuff that is more likely to take off in the long run is the stuff that's talking about servers," Smart says. "I don't know anyone else outside MIT who's looking at that."

Smart cautions, however, that the work of Goldwasser and her colleagues is unlikely to yield practical applications in the near future. "In security, and especially cryptography, it takes a long time to go from an academic idea to something that's actually used in the real world," Smart says. "They're looking at what could be possible in 10, 20 years' time."

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