Parents at an amusement park know the challenge of picking out their child’s voice, or even hearing their own hollering, in the noise of the crowd. Yelling won’t help much if the rest of the crowd is yelling also. Acoustic engineers know that raising the volume while playing back a noisy tape amplifies the noise as well as the signal. Cells have a novel way of meeting this challenge, as two Japanese mathematical biologists discuss in PNAS.1 Cells are continuously sending and receiving chemical messages, a process called signal transduction. Treating the cell signal transduction network like a physical system of receivers and amplifiers, the researchers noted that a cell, like an amusement park, is an intrinsically noisy place, yet some of the reactions are very sensitive. “How cells respond properly to noisy signals by using noisy molecular networks is an important problem in elucidating the underlying ‘design principle’ of cellular systems,” they say in the introduction. How do the sensitive reactions get their messages through all that noise? Because intracellular processes are inherently noisy, stochastic reactions process noisy signals in cellular signal transduction. One essential feature of biological signal transduction systems is the amplification of small changes in input signals. However, small random changes in the input signals could also be amplified, and the transduction reaction can also generate noise. Here, we show theoretically how the abrupt response of ultrasensitive signal-transduction reactions results in the generation of large inherent noise and the high amplification of input noise. The inherently generated noise propagates with amplification through intracellular molecular network. We discuss how the contribution of such transmitted noise can be shown experimentally. Our results imply that the switch-like behavior of signal transduction could be limited by noise; however, high amplification reaction could be advantageous to generate large noise, which would be essential to maintain behavioral variability.They categorized the noise as intrinsic, coming from the reaction itself, to extrinsic, coming from other reactions. This is somewhat like hearing your own voice vs. the yelling of those around you. The intrinsic noise has higher frequency than the extrinsic noise. As one source of noise becomes dominant, it reaches a crossover point where the other source is less dominant. This provides a kind of signal, or switch, which the cell can use to advantage:From our result, it can be further suggested that if the extrinsic noise dominates, the upstream reactions affect the fluctuation of the most downstream reaction, which determines the cellular behavior. As a result, the behavioral fluctuations are made up of the contributions of the fluctuations of several upstream reactions. On the other hand, if the intrinsic noise dominates, only the intrinsic noise of the most downstream reaction determines the behavioral fluctuations. As a result, the behavior could be simpler than the case in which extrinsic noise is dominant…. ….Consequently, the low-frequency modulations in the downstream reactions can be affected by the behaviors of upstream reactions, whereas the high-frequency modulations are expected to be independent of upstream reactions.As a result, a bacterium can respond to chemicals in the environment, the hemoglobin in your blood can respond to changing conditions in the capillaries, genes can respond correctly to requests for expression, and complex cascades of cellular reactions can respond to the signal from any reaction in the series, in the midst of all the noise. “Therefore,” they conclude, “the result implies that the extrinsic noise is essential to maintain the behavioral variability in wild-type bacteria.” Their experiments related to three relatively simple reactions, and their analysis considered primarily linear response. Many cellular reactions involve nonlinear behavior. “In these cases,” they admit, “the relation between the response and the fluctuations can be more complicated than the relations we studied.” The authors made no attempt to explain how these capabilities evolved.1Tatsuo Shibata and Koichi Fujimoto, “Noisy signal amplification in ultrasensitive signal transduction,” Proceedings of the National Academy of Sciences USA, 10.1073/pnas.0403350102, published online before print December 29, 2004.Evolutionists accuse the intelligent design movement of never publishing anything, and then cry foul when they do (see 09/08/2004 and 12/28/2004 headlines). Actually, there are thousands of ID papers, and they are published regularly, not in obscure outlets, but in the major, high-impact journals. They may not mention the buzzword “intelligent design” explicitly, but they do everything the ID movement advocates: explore the design of a phenomenon as if it has a purpose, follow the evidence where it leads, and leave the philosophical or religious implications to the reader. We regularly highlight such articles right here (see 11/10/2004, 10/27/2004, 10/27/2004, and 09/22/2004 headlines for a few recent examples). Notice how these authors used the phrase “design principle” but had no use for the evolutionary hypothesis. Very few papers try to explain in any detail how a complex feature evolved. Most, if they mention evolution at all, merely assume it in passing, as if fulfilling the obligatory pinch of incense to Father Charlie (see 11/18/2004 and 11/04/2004 and 10/01/2004 recent examples). If the criteria were rearranged with these considerations in mind, the ID movement could claim the vast majority of scientific papers as their own, and the Darwin Party would be left with a handful of just-so stories. Demand a recount.(Visited 9 times, 1 visits today)FacebookTwitterPinterestSave分享0
If creationism is so discredited as to not warrant any further discussion, some science writers are sure going out of their way to refute it. Some recent examples:Eye of the Hydra: Little sea creatures known as hydrae have light-sensitive molecules called opsins, reported Science Daily. Scientists think the opsin proteins, which exist all over the tiny animals but are concentrated near the gut, help the hydra find its prey. Todd Oakley, a notable anti-creationist involved in the study, used this as a barb against Darwin doubters:Oakley said that anti-evolutionists often argue that mutations, which are essential for evolution, can only eliminate traits and cannot produce new features. He goes on to say, “Our paper shows that such claims are simply wrong. We show very clearly that specific mutational changes in a particular duplicated gene (opsin) allowed the new genes to interact with different proteins in new ways. Today, these different interactions underlie the genetic machinery of vision, which is different in various animal groups.”Yet the story begs the question that mutational evolution produced the opsins or led to their function. A team member illustrated the circular thinking when he inferred, “because we don’t find them in earlier evolving animals like sponges, we can put a date on the evolution of light sensitivity in animals.” Another problem with the idea that evolution produced it is that it pushes the origin of light sensitivity further back in the evolutionary time frame to 600 million years ago. See also Live Science.Skull of the St. Bernard: In a surprising display of misunderstanding of the issues, a University of Manchester press release claimed that artificial selection in St. Bernard dogs refutes creationism. The skull shape in St. Bernards has changed a little in 120 years since the breed standard was defined. These changes “evolved purely through the selective considerations of breeders.” But this is, of course, artificial selection – not natural selection. The press release continues,“Creationism is the belief that all living organisms were created according to Genesis in six days by ‘intelligent design’ and rejects the scientific theories of natural selection and evolution. “But this research once again demonstrates how selection – whether natural or, in this case, artificially influenced by man – is the fundamental driving force behind the evolution of life on the planet.”A quick check of creationist literature would have shown that not even the most literal Biblical creationist believes God created St. Bernards directly. Creationist books and lectures often include diagrams of all the various dog breeds, from St. Bernards to poodles to Dobermans, as descended from an original dog kind that was probably like a wolf. Many would include all the wolves, coyotes, dingoes and foxes in the original dog kind. In addition, most creationists would admit an extensive amount of natural and artificial selection in the sorting out of traits in dog populations since the creation. Even in this press release, the dogs started and ended as St. Bernards – one variety within one species – so there was no “origin of species” or variation on the scale Darwin envisaged. EurekAlert, a news service of the American Association for the Advancement of Science, reproduced this press release without alteration; so did Science Daily.Brain of the Behe: Science (Oct. 20) gave Michael Behe 200 words to clarify a point, but then let Sean Carroll have 500 words to trash it. A complete account is given at Access Research Network by David Tyler. The lopsided exchange omitted the fact that Behe has written extensive responses to Carroll on his Amazon blog, as noted by Anika Smith at Evolution News, and to many of his other critics, as noted by Robert Crowther on Evolution News. Science, by picking and choosing a small portion of Behe’s writing, gave the distinct impression that he was conceding a major point of Darwinism, when in fact Behe proceeded beyond the quoted part to explain why it was irrelevant to evolutionary theory. Carroll, nonetheless, accused Behe of a “complete disregard of a massive literature surrounding protein interactions crucial to Behe’s entirely unfounded conclusion.” Carroll did not cite any examples of such literature.It is appalling to see the low level of intellectual rigor in the typical science press release these days when they deal with matters of creation vs evolution, and the deliberate anti-creationist bias in the journals. In the typical popular science report, creationism, when mentioned at all, is made into a caricature, a straw man to ridicule and shoot down. Don’t they realize that refuting an accurate presentation of an opponent’s view is more likely to succeed in the long run? Maybe they know they cannot. They use the only weak munitions they have: the pop-guns and spitballs of propaganda. We hope our readers appreciate the detail and fairness in these pages. Links to all the original sources are provided so you can check whether what is represented here is in fact what the evolutionists are claiming. Much of our reporting comes straight from the original science journals. While we try to present the news in ways that are thought-provoking and occasionally entertaining, we do not pander to ignorance or bias. We do not regurgitate the party-line talking points. We invite the reader to investigate the evidence and evaluate the logic on both sides. After decades of Darwin-only propaganda in the news media, we hope you find this liberating. (Visited 12 times, 1 visits today)FacebookTwitterPinterestSave分享0
Relatives of passengers presumed dead on Malaysia Airlines flight 370, which disappeared off the WA coast in 2014, have pleaded with Australia not to abandon the search for the aircraft.Family members of MH370 victims met Australian investigators leading the A$180 million search for the Boeing 777 in Perth on Wednesday.They told The West Australian newspaper of their anguish and frustration that their loved ones remain lost 2 1/2 years after the plane disappeared.Jennifer Chong, whose husband Chong Ling Tan was on the doomed flight, appealed to the Australian, Chinese and Malaysian governments to continue the search.“Please don’t give up on searching for MH370, for our loved ones, for us and for the flying public,” the Victorian mother said.MH370 disappeared on March 8, 2014, after communications were cut during what was to be a routine flight from Kuala Lumpur to Beijing.The search is due to be suspended in December when Dutch search company Fugro completes the current 120,000sqkm search zone.The Australian, Malaysian and Chinese governments agreed on the suspension in July in the absence of “credible new evidence” pointing to the plane’s location.Ms Chong was among a group of Australian, Chinese, Malaysian and Indonesian relatives of MH370 victims who were in Perth to meet the crew of theFugro Equator ship, which was in Fremantle for a crew change yesterday for its search in the remote southern Indian Ocean.Malaysian Grace Nathan, whose mother Anne Daisy was on MH370, appealed for help to find evidence before the search ended in December.“It is our understanding that if they dismantle the whole search, it will take a very long time to remobilise it because they will have to have the assets come back to the location and that will take time,” she said. “It’s everyone’s best interests that something comes up sooner rather than later.”Ms Nathan, a lawyer, said she would raise the issue when the group meets Australian Transport Safety Bureau officials in Canberra on Monday.The group praised the Australian Government, which has contributed A$60 million to the search. But they were disappointed with the Malaysian Government’s handling of the tragedy.Ms Nathan said the Malaysian officials leading the investigation into the plane’s disappearance had refused to meet victims’ relatives despite repeated requests. “We don’t understand why they never want to see us, speak to us. We struggle to come to terms with this,” she said.The relatives met US lawyer and investigator Blaine Gibson, who has found 10 pieces of debris, some confirmed to be from MH370. They praised his efforts and believe it is credible evidence to continue the search.