Tag: 爱上海PY


first_imgTo trap and hold tiny microparticles, research engineers at Harvard have “put a ring on it,” using a silicon-based circular resonator to confine particles stably for up to several minutes.The advance, published recently in Nano Letters, could one day lead to the ability to direct, deliver, and store nanoparticles and biomolecules on all-optical chips.“We demonstrated the power of what we call resonant cavity trapping, where a particle is guided along a small waveguide and then pulled onto a micro-ring resonator,” explains Kenneth Crozier, an associate professor of electrical engineering at the Harvard School of Engineering and Applied Sciences (SEAS) who directed the research. “Once on the ring, optical forces prevent it from escaping, and cause it to revolve around it.”The process looks similar to what you see in liquid motion toys, where tiny beads of colored drops run along plastic tracks—but on much smaller scale and with different physical mechanisms. The rings have radii of a mere 5 to 10 micrometers and are built using electron beam lithography and reactive ion etching.Specifically, laser light is focused into a waveguide. Optical forces cause a particle to be drawn down toward the waveguide, and pushed along it. When the particle approaches a ring fabricated close to the waveguide, it is pulled from the waveguide to the ring by optical forces. The particle then circulates around the ring, propelled by optical forces at velocities of several hundred micrometers-per-second.While using planar ring resonators to trap particles is not new, Crozier and his colleagues offered a new and more thorough analysis of the technique. In particular, they showed that using the silicon ring results in optical force enhancement (5 to 8 times versus the straight waveguide).“Excitingly, particle-tracking measurements with a high speed camera reveal that the large transverse forces stably localize the particle so that the standard deviation in its trajectory, compared to a circle, is as small as 50 nm,” says Crozier. “This represents a very tight localization over a comparatively large distance.”The ultimate aim is to develop and demonstrate fully all-optical on chip manipulation that offers a way to guide, store, and deliver both biological and artificial particles.Crozier’s co-authors included Shiyun Lin, a graduate student, and Ethan Schonburn, a research associate, both at SEAS.The authors acknowledge funding from the Harvard Nanoscale Science and Engineering Center (NSEC) and the Center for Nanoscale Systems at Harvard, both supported by the National Science Foundation (NSF).last_img read more


first_imgHarvardX, the University-wide strategic initiative begun in 2012, has created a wealth of content in a broad portfolio of online courses, including videos, recorded lectures, illustrations, and text pages. To date, educational assets in a HarvardX course were only accessible after registering for and taking a course on edX, an independent online learning platform. But with the beta launch of the HarvardDART (Digital Assets for Reuse in Teaching) tool, all of those educational resources will be easily searchable and accessible to Harvard professors looking to embed HarvardX content in their classroom courses.HarvardX’s online learning content will now become part of a larger body of work, one that can be shared across the University’s Schools and disciplines. That will advance learning by giving professors access to a wealth of their colleagues’ teaching resources, thereby furthering connections and collaboration while driving education forward.“HarvardX has worked to ensure that its amazing educational content impacts learners across the globe and on Harvard’s campus,” said Peter K. Bol, Harvard’s vice provost for advances in learning (VPAL) and Charles H. Carswell Professor of East Asian Languages and Civilizations. “DART will make it far easier for our faculty to access and use HarvardX assets in Harvard classrooms.”Through HarvardDART… “users can see that we’re not just teaching a set of individual classes but providing a broad and integrated curriculum,” said Dustin Tingley (standing, second from left), faculty director of the VPAL-Research team. Also working on the project were Andrew Ang (standing, from left), VPAL-Research data engineer; Tingley; and HUIT’s technical lead Phil McGachey and software engineer Elliott Yates (seated, left); and Daniel Seaton, senior research scientist, VPAL-Research. Photo by Silvia MazzocchinDART has produced a notable collaboration in its own right, as the VPAL research team, Harvard University Information Technology (HUIT), and HarvardX worked together to create the tool.“Making it easier for faculty and students to teach and learn is central to HUIT’s mission,” said Alan Wolf, managing director for HUIT’s academic technology services. “We were pleased to collaborate with the vice provost for advances in learning research team and HarvardX to create the DART tool, which will work seamlessly with existing University technology.”As part of a beta launch, search and preview of HarvardX resources within the DART application are now available to the Harvard community on campus or through VPN.Later this year, Harvard professors will be able to integrate these assets directly in Harvard’s learning management system, Canvas, so their students can use them.According to Robert A. Lue, HarvardX faculty director and professor of the practice of molecular and cellular biology, DART will make a significant stockpile of material available for residential classes. “It applies to everything — all topics, all courses — and will provide a One Harvard experience,” he said. “It’s a key way for every Harvard faculty member to know what’s available for every topic area from HarvardX and plug it into the Canvas learning management system, to make all of HarvardX’s content usable and pluggable.”Lue said the need for a tool like DART was recognized when HarvardX was launched. “As HarvardX was building up a repository of content, we wanted ways you could select it for use in different bite sizes — whole courses, videos, or portions of courses. When you have lots of compelling material, you need a mechanism to allow an audience to find and reuse what they need. At first we didn’t have the critical mass of content to test if such a thing would work well, but now we have enough content across enough different fields. So DART could not be a more welcome step in the process of making HarvardX materials more available.”“DART allows you to explore common themes and connections between different contexts,” said Dustin Tingley, faculty director of the VPAL research team and professor of government. “Users can see that we’re not just teaching a set of individual classes but providing a broad and integrated curriculum. If you wanted to, you could go on the edX site and enroll in different classes, but you’d never get to search through the individual assets that are part of the courses. For instance, I may not want to take the class on U.S. national security. But if I can find [Harvard Kennedy School’s Douglas Dillon Professor of Government] Graham Allison talking about the Cuban Missile Crisis, that’s an incredible piece of content.”Aside from the practical use, DART will offer faculty members greater insight into each other’s courses. “We think that gradually Harvard faculty will discover what some of their colleagues have been saying, as well as find some of the assessments, simulations, animations, and visualizations, useful in their own classes,” said Bol. “Providing our faculty more access to their peers’ instructional materials should inspire deeper conversations on teaching and learning.”Once DART assets are available for Canvas integration for the fall semester, professors will be able to add HarvardX resources to their residential courses in just a few clicks. The database is searchable by keywords. Users who search the word “moon,” for instance, will find any lunar-themed content within a HarvardX course, whether it be scientific astronomy lectures or a recitation of a Chinese poem about the moon. The preview function allows the viewer to watch or access any HarvardX asset that’s available. By later this year, it will only take another click to add the material to faculty course assets.“Faculty will have great flexibility in how they approach blending their courses with HarvardX material,” said VPAL senior research scientist Daniel Seaton, who helped develop DART. He expects that much of the content will be well suited to existing residential courses. “Massive Open Online Course [MOOC] content generally has really high production values. Faculty have some guarantee that the content was curated and generated for broad audiences.”Phil McGachey, HUIT technical lead and architect, confirmed that the technical feat of indexing HarvardX resources for search and reuse should have a lasting impact on how institutions make use of their existing and future MOOC content.“Prior to DART, one could only search minute-and-a-half preview videos for HarvardX courses. DART allows search and preview of individual videos, problems, and text pages. In the future, the task of embedding HarvardX content in residential courses — a task that previously required substantial technical overhead — will take place with a click of a button.” McGachey said.“VPAL-Research’s collaboration with HUIT to produce DART will open up many opportunities for use of this technology,” added Tingley.Ultimately, every Harvard course will have access to a wider range of material, and HarvardX resources will be shared across disciplines, allowing poets and astronomers who study the moon to learn from each other.“Does this mean that all Harvard courses are going to merge into one gigantic thing? I don’t think that will be the case,” Lue said. “But there will be groupings of courses that share the material very freely. And I think that increasingly we’ll see faculty sharing what they’re doing and being inspired by each other.”This also suggests that courses will become less self-contained. “Very few courses are self-contained as it is,” Lue said. “You always incorporate issues, graphics, and ideas from other courses. But DART will facilitate sharing of the top-level digital content that we’ve created. It will make courses better. They’ll have a richer array of things to utilize.”last_img read more


first_imgAnd more broadly, 72 percent of exoneration cases in which the defendant was sentenced to death involved misconduct by police and prosecutors.”Misconduct is generally more common the more extreme the violence,” the study says.The report comes from a joint project of University of California-Irvine, the University of Michigan law school, and Michigan State University law school.It cites a broad range of police and prosecutor misconduct that contributes to unjust convictions: using questionable techniques to force false confessions, encouraging or coercing witnesses to provide evidence against a defendant; fabricating evidence; and prosecutors skirting the law. Around 2,500 people have been exonerated of serious crimes after being falsely convicted over the past 30 years in the United States.According to a new study out Tuesday, in around half their cases, police and prosecutors withheld evidence that would have exculpated them.The study by the National Registry of Exoneration found that evidence that would have cleared the defendant was withheld in 61 percent of erroneous murder convictions. African Americans were slightly more likely than whites to be victims of misconduct leading to false convictions.But in some types of crime, blacks were far more often falsely convicted. In drug cases, blacks were 12 times more likely than whites to be falsely convicted.Yet whites were also frequent victims, especially in so-called white-collar crimes involving corruption and fraud.In such cases, the police were not the problem, but instead zealous federal prosecutors likely seeking to prove themselves with a conviction.The consequences of injustice can be heavy: the average time spent in jail by a person convicted for murder and later cleared of the crime was 13.9 years, according to the study.An example is the case of Michael Morton, convicted of murder in Texas in 1987.The report said county prosecutor Ken Anderson “concealed potent exculpatory evidence that could have cleared Morton and led to the real killer – who killed another woman in 1988.”Sentence to life in prison, Morton was exonerated by DNA in 2012.Addressing the problem is difficult, the study admits.There is a deep, hard-to-change culture in police departments that is focused on getting convictions and resisting criticism, and includes pervasive practices that permit or reward bad behavior, it said.And prosecutors have unreviewable power on who to charge and for what, and can push the sentences they want.Topics :last_img read more


first_imgThere will be plenty of tension on the pitch in Sunday’s eagerly anticipated fixture.Barca will be keen to further cement their domestic hegemony over Madrid and extend their gap over them to 18 points, which would be the biggest gap they have ever held over their rivals.Zinedine Zidane’s side can avenge December’s humiliating 3-0 home defeat by Barca by snapping the Catalans’ Liga record of 42 games without defeat.Zidane has already angered Barca by declaring his side will not give the newly crowned champions a guard of honour before kickoff, a gesture the Catalans did carry out in 2008 when Madrid had won the title.Sunday’s game is also the first ‘Clasico’ since 2008 to take place after the title race has been decided.Real have had a disappointing Liga campaign and could finish third for the first time in four years. But their domestic woes has not stopped them from storming into the Champions League final with a 4-3 aggregate win over Bayern Munich. In contrast Barca crashed out of Europe to AS Roma in the quarterfinals.Madrid will play Liverpool in the final in Kiev on May 26, when they will be targeting a record-extending 13th European Cup. They will also be looking to become the first team since Bayern Munich in 1976 to win the trophy three years in a row.Madrid captain Sergio Ramos believes winning Europe’s top prize again could trump Barca’s achievements on the domestic front.“Barca have had a great year, they have won two trophies and they deserve credit for that but winning the Champions League is equivalent to those two or even more,” Ramos said.He also confirmed his side would follow Zidane’s orders to deny their rivals a guard of honour.“What Zidane says is gospel. We’re making too much fuss out of all this. Barca have the title, which is what they wanted, but there will be no guard of honour, full stop,” he said.Elsewhere, Valencia can seal their return to the Champions League by clinching fourth spot if they win at local rivals Villarreal on Saturday.Getafe, Sevilla, Girona and Real Sociedad will continue to fight for seventh spot and a place in next season’s Europa League, with three points separating the four teams.Malaga, Las Palmas and Deportivo La Coruna have already been relegated.Share this:FacebookRedditTwitterPrintPinterestEmailWhatsAppSkypeLinkedInTumblrPocketTelegram La Liga and King’s Cup champions Barcelona will be flying high when they host Real Madrid on Sunday in the ‘Clasico’ but their arch rivals will be feeling equally smug after reaching the Champions League final for a third year in a row.After clinching a seventh league title in 10 years last Sunday, Barcelona’s only incentive is to finish the La Liga season without losing a game.Third-placed Real’s motivation, however, is to leapfrog Atletico Madrid, who hold a four-point advantage but have played one more game.last_img read more


first_imgGuests pictured at the launch of ‘A brush with the Wild Atlantic,’ a collection of new works by artist Sharon McDaid and ‘Select,’ an exhibition of pieces from the Donegal Designer MakersTwo exceptional new art and design collections have been going down a storm in Inishowen this week, following their launch in Carndonagh’s Silver Birch Gallery.‘A brush with the Wild Atlantic,’ is a collection of new works by artist Sharon McDaid while ‘Select’ is an exhibition of various pieces from the Donegal Designer Makers who are enjoying their first-ever exhibition in Inishowen.“We had a terrific turn out at last week’s launch and I’m delighted to say that there has been an amazing response to both collections since then,” Sharon McDaid, owner of the Silver Birch Gallery said.Sharon, who is a member of the Donegal Designer Makers, explained that their collection is one of new pieces, made specifically for the exhibition. “We have an exhibition every year and members make pieces that would be totally different to what they might do normally, based on the theme of the exhibition.This year the theme was ‘Select,’ encouraging people to select to design, to choose and to make. The collection was shown first in Ardara where the Donegal Designer Makers have a base before coming here to Carndonagh.”The visit to the peninsula, says Sharon, is the first time the Donegal Designer Makers Annual Exhibition has come to Inishowen, and she says the response has been terrific.Of course last Thursday was a night of double excitement for Sharon who also launched her own new collection. “All of the paintings in ‘A brush with the Wild Atlantic Way’ are inspired by Inishowen, the first stop on the Wild Atlantic Way. Thankfully there has been a brilliant response to that too and many of the pieces were even on reserve before they went on display,” she added.Meanwhile Ursula Donnelly of Donegal Local Enterprise Office who performed the official launch of both collections, said, with the new Creative Strategy now in place in Donegal, it is an exciting time for those involved in the creative industries.“Donegal Local Enterprise Office is delighted to have worked with both Sharon individually and Donegal Designer Makers as a group and we recognise that there is great energy among the talented people already co-creating and collaborating in Donegal. Our focus at the Local Enterprise Office within the strategy is to work with the sector to develop viable and sustainable businesses and we would actively encourage anyone in the creative industries in the county to get involved with the roll out of the strategy.”The dual collections launched last week are currently on display at the Silver Birch Gallery in Carndonagh and both exhibitions will continue to run until the end of August.If you would like a copy of the Creative Strategy for Donegal you can download it here http://bit.ly/1NnCW5r or alternatively make contact with Donegal Local Enterprise Office on 0749160735. Donegal Designer Makers can be found here http://donegaldesignermakers.com/ and the Silver Birch Studio here http://www.sharonmcdaid.com/TWO EXCITING ART COLLECTIONS LAUNCHED IN INISHOWEN was last modified: August 18th, 2015 by StephenShare this:Click to share on Facebook (Opens in new window)Click to share on Twitter (Opens in new window)Click to share on LinkedIn (Opens in new window)Click to share on Reddit (Opens in new window)Click to share on Pocket (Opens in new window)Click to share on Telegram (Opens in new window)Click to share on WhatsApp (Opens in new window)Click to share on Skype (Opens in new window)Click to print (Opens in new window)last_img read more

Recent Comments