Cells are like miniaturized cities, with elaborate transportation systems ferrying their cargo to and fro (see Feb. 25 headline). Just like a city may have railroads, busses, cars and monorails, the cell has multiple kinds of transport motors: dyneins, kinesins, and myosins. Scientists have learned that most of the roadways are like one-way monorails: actin filaments and microtubules, upon which the vehicles travel in one direction. But what if a passenger needs to jump from one system to another? ‘ No problem; the cell has mastered the art of ridesharing with its own park-and-ride system. In the Dec. 2 issue of Current Biology1, this is described by Marcus Maniak in a Dispatch entitled “A park-and-ride system for melanosomes.” Melanosomes are organelles (somes) that carry melanin, the pigment chemical that allows some organisms, including fish and amphibians, to change their skin color to match their surroundings. For this to work, the melanosomes need to hitch rides either to the exterior of the cell or the interior. He pulls together several recent findings to describe how this all works:Together these findings suggested how melanosomes might move on actin filaments and showed that this type of motility is required for the even distribution of melanosomes within the cell. From these main observations, it became clear that, during aggregation, a cytoplasmic dynein motor carries melanosomes on the radially arranged microtubules towards the cell center (Figure 1B), while during dispersion a kinesin transports the granules to the periphery (Figure 1C), where they engage via a myosin V molecule with short actin filaments to be distributed further (Figure 1D). This switching of transport systems is a kind of miniature edition of modern urban traffic, where millions of workers leave the city centers in the evening on trains and board their cars at park-and-ride stations to complete their daily journey within the green peripheral belt. (Emphasis added in all quotes.)As if that were not amazing enough, it appears that the drivers “talk” to each other with a communication system:Although the work of Rodionov et al. has moved the field a large step further, there are obviously several issues that remain to be investigated. Exciting new findings addressing the coupling of motor molecules to the melanosome surface in other experimental animals open the possibility to speculate how the motors may talk to each other on a molecular level. At least for Xenopus there is now clear evidence that both dynein and kinesin couple to melanosomes via the dynactin complex. Moreover, both motors compete for the same protein component; this could allow one motor to gain access to the microtubule while the other is prevented from engaging successfully.He describes how this “tug-of-war” competition is actually a kind of way for the motors to negotiate the right-of-way. Additional factors that attach to the vehicles or trackways may assist in making sure the rules of the road are obeyed. “Thus,” he concludes, “further exciting results are on the way to complete the picture of how melanosomes switch from one transport system to the other.”1Marcus Maniak, “Dispatch: Organelle Transport: A Park-and-Ride System for Melanosomes,” Current Biology Vol 13, R917-R919, 2 December 2003.Maniak uses the word motor 22 times in his article, which is replete with other urban metaphors: transport system (see 09/26/2002 headline), etc. Moreover, there is no mention of evolution, Darwin, or of any mechanism that might explain how this elaborate, coordinated, interconnected system could have originated. Surprised? Every muscle move you make, every breath you take, every beat of your heart, and every one of your senses are dependent on molecular machines. The study of biological motors and molecular machines is the “biology of the future” that Bruce Alberts, President of the National Academy of Sciences and editor of Molecular Biology of the Cell has stated more than once (see 01/09/2002 headline). It was also a biology the likes of which Charles Darwin and his followers could not have imagined. Had Darwin seen into the future at what Year 2003 biologists would be detecting in life’s fundamental unit, the cell, and even in the simplest micro-organisms, he well could have developed cold shudders (see 01/29/2002 headline) severe enough to have frozen his evolutionary speculations to death.(Visited 19 times, 1 visits today)FacebookTwitterPinterestSave分享0
29 October 2010South African astronomy is set to receive a major boost, in the form of R100-million, ultra-high speed broadband link between the remote Northern Cape sites of the Southern African Large Telescope and Square Kilometre Array and the SA National Research Network backbone in Cape Town.The Council for Scientific and Industrial Research (CSIR) has selected a Neotel/Broadband Infraco partnership to install the 10 gigabit per second fibre-optic link. The SA National Research Network (SANReN) backbone is an undertaking of the CSIR’s Meraka Institute.The ultra-high speed link will enable local and international researchers to process data from the Southern African Large Telescope and the Karoo Array Telescope in near real time, and significantly boost South Africa’s bid to host the Square Kilometre Array (SKA).SKA bid, MeerKAT telescopeAllied with eight other African countries, South Africa is competing against Australia (allied with New Zealand) to host the €1.5-billion SKA, a 3 000-dish radio imaging telescope massively more powerful than any such instrument ever built.As part of its SKA bid, South Africa is currently building the 80-dish Karoo Array Telescope, or MeerKAT, in a radio astronomy reserve near Carnarvon in the Northern Cape.The MeerKAT, due to be commissioned in 2014/15, will be a powerful scientific instrument in its own right – SKA South Africa recently announced that more than 43 000 hours of observation time had been allocated to radio astronomers from Africa and around the world to do research using the telescope.When the new high-speed link goes live in six to 10 months’ time, researchers will be able to get real-time access to data already being yielded by the MeerKAT’s precursor, the seven-dish KAT-7 demonstrator radio telescope.Southern African Large TelescopeThe Southern African Large Telescope (SALT), also situated in the remote Karoo region of the Northern Cape, at the site of the South African Astronomical Observatory in Sutherland, will likewise benefit from the new link.Inaugurated in November 2005, SALT – the largest single optical telescope in the southern hemisphere – has been hamstrung by both imaging problems and data communication issues.While SALT’s imaging problems have recently been sorted out, it still has to make do with a miserly four megabit per second Telkom line to Cape Town. The new link will put it in a different league altogether.‘Demonstrates our ability to invest’The installation of the new link will demonstrate “that South Africa can provide the bandwidth needed to fulfil the requirements of the full SKA, and will serve as a significant boost to the South African SKA bid,” Department of Science and Technology chief director Daniel Adams said this week.National Research Foundation CEO Albert van Jaarsveld said the development paved the way for international collaborators to actively make use of the facilities that will be provided by the two telescope sites.With the recent successful installation of seven dishes at the SKA site, the 10 Gbps link could not have come at a better time, he said, adding that researchers were eager to get access to the data being produced at the two sites.“The broadband link will enable not only South African but also international researchere to have near real-time access to the data,” he said. “Furthermore, the broadband link demonstrates our ability to invest heavily in scientific infrastructure in support of our desire to win the SKA bid.”SAinfo reporterWould you like to use this article in your publication or on your website? See: Using SAinfo material
Professor Straube mentioned that he’s been talking with HVAC equipment manufacturers about this for about a decade, and they just don’t get it. Carrier and Trane, he said, have told him they don’t sell low capacity equipment because no one’s buying it. They failed to see that if the equipment is not available, no one can buy it so of course they’re not buying it because it’s not available. Evidently those discussions haven’t turned the corner yet.Specifying low-capacity equipment won’t save you any moneyStraube covered a lot of ground in his presentation. After introducing the need for low-capacity mechanical systems and the lack of conventional equipment, he dove into the details of the different systems available, how they work, what some of the limitations are, and how difficult it is to do it right.One of the big obstacles is cost. “We’re beyond talking about saving money on equipment for low-load houses,” he said, because you won’t. If you’re a spray foam contractor, for example, trying to get builders to bite on the higher cost of foam because of savings they’ll see from smaller mechanical systems, it’s not gonna happen.You can get a 46 kBTU/hr 95 AFUE furnace for $697. If you want something with less capacity, you could go for a boiler, tankless water heater, or minisplit heat pump, all of which are significantly higher in cost.The same is true of air conditioners. When you go from a 2-ton system to a 1.5-ton system, it costs more and is less efficient, too. So if you want a low-load building to have a low-capacity mechanical system, get used to higher cost.Returning water temperature affects efficiencyIn the first half of the day, Straube went through some of the basics of efficiency ratings (SEER, EER, and COP), details about condensing boilers and furnaces, and combo systems (using one system to provide heat and domestic hot water). He talked about some of the problems with condensing systems and the temperature of the entering water or air.If you think you have a boiler that’s 95% efficient, for example, you may not be getting that if the water returning in the hydronic distribution system comes back too warm. Condensing boilers and furnaces work by extracting the latent heat from the water vapor in the exhaust gases. They’re able to do so as long as the heat exchanger is below the dew point. If the returning water (or air in an air distribution system) is above the dew point, the water vapor doesn’t condense, the boiler/furnace doesn’t extract as much heat, and the efficiency goes down. The graph of condensation efficiency shows how the efficiency changes with returning water temperature.Desuperheaters? Thumbs downAfter lunch, the discussion turned to heat pumps, both conventional, ground source, and minisplits. He blasted the idea of using desuperheaters on ground-source heat pumps to get hot water because they’re usually not cost-effective and don’t give you much hot water. Ground-source heat pumps work well in school-sized buildings, he said, but not so well for low-load buildings or really big buildings. He also said that he has not seen any third party data on GSHP efficiency showing a COP higher than about 3. Since the industry doesn’t include pump or blower energy in their COP calculations, Straube said, their COP numbers are higher but don’t give the complete picture.The topic was mechanical systems, so there was also talk about water heating. Combo systems give you both heat and hot water, and some people use water heaters just for space heating, too. Straube mentioned that HVAC and DHW need to come together.Looking back over my notes now, I still can’t believe how much material he covered. It really was a tsunami of information. He also spoke briefly about using CO2 as a refrigerant in air-to-water heat pumps, which allows true hot water production because they can get higher temperatures than the standard refrigerants; electric resistance heat, which is OK in some cases for low-load buildings; Legionnaire’s disease, which can be a problem if the DHW temperature is too low; heat pump water heaters; distribution of thermal energy (air, water, radiant); and more.The wit of Professor StraubeAs I mentioned at the beginning, Professor Straube is not only incredibly knowledgeable, he’s also a walking quote machine. Here are a few of the many witticisms we were treated to yesterday:Caveat emptor is Latin for “you’re gonna get screwed.”Cats are IAQ problems and you’d have to pass them through the HRV to solve that problem. But they’re not really a cat anymore after that.Recirculating range hoods don’t solve the IAQ problem. It’s like a recirculating toilet. The stuff just goes round and round and never leaves.In San Francisco, it never gets really hot or really cold. Buildings are there mainly to keep people away from your stuff.It’s taken America 10 years to realize that tankless water heaters work better with tanks.If you ever get a chance to go to one of his talks, I guarantee you won’t have any trouble staying awake and engaged.A great reason to be a GBA Pro!Not everyone can take the time to go off to New England for two days to attend a session like this. The good news is that many people watched the whole thing from their home or office because Green Building Advisor ran a livecast of the sessions.Anyone could have signed up through Building Science Corporation for the regular fee of $395 per day. GBA Pro members, however, got access to the livecast as part of their membership. What a deal! GBA Pro members will also get to watch some of the recorded videos from the Building Science Experts’ Session once they’re posted. Stay tuned!Allison Bailes of Decatur, Georgia, is a speaker, writer, energy consultant, RESNET-certified trainer, and the author of the Energy Vanguard Blog. You can follow him on Twitter at @EnergyVanguard. RELATED ARTICLESChoosing HVAC Equipment for an Energy-Efficient HomePodcast: The Green Architects Chat With John StraubeHeating a Tight, Well-Insulated HouseJust Two Minisplits Heat and Cool the Whole House Will Minisplits Replace Forced-Air Heating and Cooling Systems?Goodbye Radiant FloorQ&A: Heating and ventilating a very small spaceARTICLES BY JOHN STRAUBEComparing Passivhaus Standard Homes to Other Low-Energy HomesThe History Of InsulationHow Air Affects a House (1)How Air Affects a House (2)How Heat Moves Through BuildingsWhy Does Green Building Matter? (1) Why Does Green Building Matter? (2) Professor John Straube spoke for a whole day at the Building Science Corporation’s Experts’ Session earlier this month. His topic, a good one for GBA readers, was mechanical systems for low-load buildings.You know that expression about how the information comes at you so fast in some classes that it’s like drinking from a firehose? With Professor Straube, it’s like trying to drink from a tsunami! The guy has not only a phenomenal knowledge but he’s also a fantastic teacher and incredibly witty.Giving you a good overview of everything Straube talked about would be quite a challenge (and result in an article longer than anything Martin Holladay has written here!), because he really covered the whole gamut of this topic. So, I’ll throw out a few highlights of the day here and encourage you to attend one of his workshops if you ever get the chance.You may also get the opportunity some day to buy his book on this topic. As we were talking on the last night, Joe Lstiburek and others strongly encouraged Straube to get this knowledge into a book, and I hope he does.It’s hard to find a furnace rated at less than 40,000 Btu/hBuilding enclosures have improved dramatically in the past two decades. We have more insulation, better windows, and sealed air barriers. Many homes have peak heating loads of 15 to 30 thousand BTU per hour (kBTU/hr) — even in cold climates. This applies to large houses and buildings, too, because high performance enclosures result in zones with low loads. The problem is that most conventional heating equipment available doesn’t go that low in capacity. About the smallest furnace you can get is 40 kBTU/hr.
In a bid to give fillip to health services in poverty-stricken KBK region of Odisha, the State government has proposed to establish 19 hospitals in 18 districts on public-private partnership mode.The Empowered Committee on Infrastructure, which met under the chairmanship of Chief Secretary Aditya Prasad Padhi here on Monday, decided to set up new quality care hospitals mostly in KBK (Kalahandi Balangir and Koraput) and KBK+ districts like Boudh, Kandhamal and Gajapati.“It was proposed to establish 19 hospitals in 18 districts chosen on the parameters of backwardness in health indicators. These hospitals would be of two categories. One type would be 100-bedded and another type would be 200-bedded,” said State Health Secretary P.K. Meherda.Sops galore“The government would provide land at concessional rate and other infrastructural facilities and the tariff of treatment in these hospitals would be decided by the government. The private parties would make necessary investments for setting up the hospitals and they would bring in more specialists and clinical professionals,” the Health Secretary informed. The State government organised an investors’ conference to get inputs from interested parties regarding the feasibility of the project and the methods of its operation. Around 71 organisations participated in the event and expressed interest to invest in the project.Sources in the Health Department said the project would create direct employment opportunity for 9,500 people while total private sector investment would be around ₹1,150 crore.
Don’t miss out on the latest news and information. Grace Poe files bill to protect govt teachers from malicious accusations Private companies step in to help SEA Games hosting Jayson Castro. Photo by Tristan Tamayo/INQUIRER.netJayson Castro knew he had to take matters into his own hands after TNT opened the season with two straight losses.And with Castro showing the way, the KaTropa have strung up a couple of wins.ADVERTISEMENT Oil plant explodes in Pampanga town LATEST STORIES US judge bars Trump’s health insurance rule for immigrants MOST READ View comments Oil plant explodes in Pampanga town SEA Games hosting troubles anger Duterte Sports Related Videospowered by AdSparcRead Next Lacson backs proposal to elect president and vice president in tandem ‘We are too hospitable,’ says Sotto amid SEA Games woes Mighty Sports faces Magnolia in tuneup ahead of Dubai tilt Castro was at his best on Sunday in a showdown against reigning four-time Philippine Cup champion San Miguel Beer.The 32-year-old Castro put up 24 points, 11 assists, five rebounds and four steals to lead the KaTropa past the Beermen, 104-93.FEATURED STORIESSPORTSPrivate companies step in to help SEA Games hostingSPORTSUrgent reply from Philippine football chiefSPORTSWin or don’t eat: the Philippines’ poverty-driven, world-beating pool starsHe averaged 16.5 points, 4.0 rebounds, 6.5 assists and 2.5 steals in TNT’s last two games to nab the PBA Press Corps Player of the Week citation.Castro bested his teammate Troy Rosario and Ryan Reyes, Rain or Shine’s Gabe Norwood and Mark Borboran, along with Phoenix forward Calvin Abueva, Jason Perkins and Matthew Wright for the weekly honor. PH underwater hockey team aims to make waves in SEA Games PLAY LIST 02:42PH underwater hockey team aims to make waves in SEA Games01:44Philippines marks anniversary of massacre with calls for justice01:19Fire erupts in Barangay Tatalon in Quezon City01:07Trump talks impeachment while meeting NCAA athletes02:49World-class track facilities installed at NCC for SEA Games02:11Trump awards medals to Jon Voight, Alison Krauss