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Giga Moravac

Nemam gde da  pitam pa cu da pitam ovde. Radi se o stepenu srodstva.

 

Dakle, da li sam sa rodjenom sestrom u blizem, daljem ili istom stepenu srodstva ili sa roditeljima?

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Delija67

daljem

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Zverilla

da, ali samo za dlaku daljem (ako se ignorise x hromozom i mitohondrijalna dnk, onda je genetska slicnost 1/2 u oba slucaja).

tako da zavisi malo i od definicije stepena srodstva ;)

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bigvlada

 

VR helps surgeons to 'see through' tissue and reconnect blood vessels
by Staff Writers
London UK (SPX) Feb 05, 2018

augmented-reality-surgery-hg.jpg
This is the surgeon's view. Image courtesy 'Philip Pratt, et al. Eur Radiol Exp, 2018'

Using augmented reality in the operating theatre could help surgeons to improve the outcome of reconstructive surgery for patients. In a series of procedures carried out by a team at Imperial College London at St Mary's Hospital, researchers have shown for the first time how surgeons can use Microsoft HoloLens headsets while operating on patients undergoing reconstructive lower limb surgery.

The HoloLens is a self-contained computer headset that immerses the wearer in 'mixed reality', enabling them to interact with 'holograms' - computer-generated objects made visible through the visor. In the UK, headsets are currently only available for developers.

The Imperial team used the technology to overlay images of CT scans - including the position of bones and key blood vessels - onto each patient's leg, in effect enabling the surgeon to 'see through' the limb during surgery.

According to the team trialling the technology, the approach can help surgeons locate and reconnect key blood vessels during reconstructive surgery, which could improve outcomes for patients.

"We are one of the first groups in the world to use the HoloLens successfully in the operating theatre," said Dr Philip Pratt, a Research Fellow in the Department of Surgery and Cancer and lead author of the study, published in European Radiology Experimental.

"Through this initial series of patient cases we have shown that the technology is practical, and that it can provide a benefit to the surgical team. With the HoloLens, you look at the leg and essentially see inside of it. You see the bones, the course of the blood vessels, and can identify exactly where the targets are located."

Following a car accident or severe trauma, patients may have tissue damage or open wounds that require reconstructive surgery using fasciocutaneous flaps. These flaps of tissue, which are taken from elsewhere on the body and include the skin and blood vessels, are used to cover the wound and enable it to close and heal properly.

A vital step in the process is connecting the blood vessels of the 'new' tissue with those at the site of the wound, so oxygenated blood can reach the new tissue and keep it alive.

The standard approach for this element of reconstructive surgery has been the use of a handheld scanner which uses ultrasound to identify blood vessels under the skin by detecting the movement of blood pulsing through them, enabling the surgeon to approximate where the vessels are and their course through the tissue.

"Augmented reality offers a new way to find these blood vessels under the skin accurately and quickly by overlaying scan images onto the patient during the operation," explained Dr Pratt.

Making The Model
In the procedures used to trial the technology, five patients requiring reconstructive surgery on their legs underwent CT scans to map the structure of the limb, including the position of bones and the location and course of blood vessels.

Images from the scans were then segmented into bone, muscle, fatty tissue and blood vessels by Dr Dimitri Amiras, a consultant radiologist at Imperial College Healthcare NHS Trust (ICHNT), and loaded into intermediary software to create 3D models of the leg.

These models were then fed into specially designed software that renders the images for the HoloLens headset, which in turn overlays the model onto what the surgeon can see in the operating theatre. Clinical staff are able to manipulate these AR images through hand gestures to make any fine adjustments and correctly line up the model with surgical landmarks on the patient's limbs, such as the knee joint or ankle bone.

Dr Amiras said: "St Mary's Hospital is a major trauma centre, giving us the opportunity to try and improve the pre-operative planning for reconstructive flaps. Over time, the scanning protocol has been optimised to give excellent images of the anatomy, however, at first we had to rely on rough measurements of anatomical landmarks taken from 3D CT reconstructions to guide surgery.

"Now, using the HoloLens, we can identify where the blood vessels are in 3D space and use virtual 3D arrows to guide the surgeon. Currently, data preparation is a time consuming process, but in the future much of this could be automated, with the consultant radiologist checking the accuracy of the model against the original scan. I think this is a great example of what can be achieved in an Academic Health Science Centre."

The Surgeon's View
Mr Jon Simmons, a plastic and reconstructive surgeon at ICHNT, led the team who carried out the procedures using the HoloLens headset and augmented reality models. The cases ranged from a 41-year-old man who had sustained leg injuries during a car accident, to an 85-year-old woman with a compound fractured ankle. The surgical teams reported the HoloLens to be a powerful tool in the theatre, with the approach being more reliable and less time-consuming than the ultrasound method of locating blood vessels.

"The application of AR technology in the operating theatre has some really exciting possibilities," said Mr Simmons. "It could help to simplify and improve the accuracy of some elements of reconstructive procedures. While the technology can't replace the skill and experience of the clinical team, it could potentially help to reduce the time a patient spends under anaesthetic and reduce the margin for error. We hope that it will allow us to provide more tailored surgical solutions for individual patients."

The group highlights a few limitations with the technology, which could include errors during the modelling stages as well as the potential for the overlaid model to be misaligned. In addition, the case studies so far have been based on the leg, which has a number of clearly visible surgical 'landmarks', such as the ankle or knee. Areas without these rigid landmarks, such as abdomen, may be more complicated with a greater potential for movement of blood vessels.

However, the researchers are confident that, once refined, the approach could be applied to other areas of reconstructive surgery requiring tissue flaps, such as breast reconstruction following mastectomy. The next steps include trialling the technology in a larger set of patients, with procedures carried out by teams at multiple centres.

Dr Pratt added: "In future we hope to automate the process further. We can use software to improve the alignment and will attach markers to the patient when they have the scan, with the same markers present during the operation to use as additional points of reference. There are a number of areas we would like to explore, and further improvements are needed, but the small case series has shown that for reconstructive surgery, this seems to be a valuable tool in the operating theatre."

Research Report: 'Through the HoloLens looking glass: augmented reality for extremity reconstruction surgery using 3D vascular models with perforating vessels' by Philip Pratt et al. is published in the journal European Radiology Experimental.

http://www.spacedaily.com/reports/Augmented_Reality_helps_surgeons_to_see_through_tissue_and_reconnect_blood_vessels_999.html

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bigvlada

hmm, hajde ovo ovde. Menjaju konačno i kilogram.

 

The kilogram gets a makeover

January 26, 2018, National Research Foundation

 

In Sèvres, a small commune on the outskirts of Paris, lies a gleaming lump of metal the size of a palm. Le Grand K, or Big K as they call the platinum and iridium alloy, sits underground in a high-security vault. It is held under three glass bell jars, and can only be retrieved using three separate keys, each held by different individuals.

 

Contrary to appearances, tampering and theft isn't the utmost concern for those who guard Big K. Instead, the artifact's custodians have spent recent years worrying that the alloy isn't quite living up to the reputation that it's held for the past century—that it's no longer exactly one kilogram in mass, but micrograms lighter.

 

Being off by roughly the weight of a grain of sand might seem trivial, but Big K is the International Prototype of the Kilogram. In other words, it's the gold standard by which all other kilograms in the world are measured against. The tiniest discrepancy in Big K's accuracy impacts fields such as medicine, electronics and engineering, sectors where precise measurements are paramount. But a fluctuating kilogram also has rippling effects on other phenomena—such as force, energy and luminous intensity—that use it as the building block for measurements.

 

Because of the wide-reaching consequences an imprecise Big K holds, scientists are now searching for a more reliable and stable standard for the kilogram—one that doesn't centre on a single piece of metal. Their aim: to redefine the kilogram using a new physical standard by the end of 2018.

 

"We are about to witness a revolutionary change in the way the kilogram is defined," said physicist Klaus von Klitzing while speaking at CERN last October. Von Klitzing, who won the 1985 Nobel Prize in Physics, is one of the scientists involved in the kilogram's makeover.

 

The change, many argue, is long overdue. The kilogram is one of seven base units that comprise the International System of Units (SI), the most widely used measurement system in the world today. Originally both the kilogram and the metre were defined by prototypes and the time was fixed by the earth rotation, however in the meantime more and more base units are connected to physical quantities of nature that remain the same regardless of time or location.

 

One second, for example, is defined as the time it takes for the cesium-133 atom to complete 9,192,631,770 periods of radiation for a specified transition. One metre used to be represented by a metal bar stored alongside Big K in France, but is now defined by how far light travels in a vacuum during 1/299,792,458 of a second.

 

The kilogram remains the only SI unit represented by an unstable artifact. So in 2014, members of the General Conference on Weights and Measures, the international body which oversees the SI system, voted to redefine the kilogram in terms of Planck's constant, a fundamental constant of quantum mechanics.

 

The redefinition is a big deal, says John Pratt of the National Institute of Standards and Technology (NIST), the body responsible for the standardisation of weights and measures in the United States. The new definition means we can switch from "a 19th century definition of mass to a more 21st or 22nd-century definition of mass," Pratt said. "We could get it based on an idea more than an object."

 

When the gold standard is unstable, as Big K has proved, it's a "huge inconvenience," said Pratt. Big K's unaccounted weight loss means its sister cylinders—cast from Big K and shipped around the world for calibration—are no longer identical to the gold standard. NIST's copies, for example, differ from Big K by roughly 45 micrograms, the weight of an eyelash. That wreaked havoc several years ago, leading to NIST re-issuing certificates for its kilograms, and companies producing weights based on NIST's standards having to manufacture new ones.

 

Re-defining the kilogram according to Planck's constant will help avoid such problems altogether. However, physicists need to first get a good enough measure of Planck's constant, the quantum-mechanical number that relates how a particle's energy is related to its frequency and, through E=mc2, to its mass. Once scientists assign an exact fixed value to Planck's constant, they'll be able to derive a new definition for the kilogram.

 

Two types of experiments are currently underway, both seeking to measure Planck's constant with extraordinary precision. The first is the Avogadro Project, led by an international team of scientists. It involves counting the number of atoms in two spheres of silicon that each weigh the same as Big K. With this number—the precise number of atoms comprising a particular substance—researchers can calculate Avogadro's constant, convert it into a value for Planck's constant and thus relate the kilogram to atomic mass.

 

The second method uses a device called a watt, or Kibble, balance. It's a scale of sorts that produces a value for Planck's constant by measuring a one-kilogram test mass, calibrated using Big K, against an electromagnetic forces. Planck's constant is proportional to the amount of electromagnetic energy required to balance the mass.

 

In order to calculate the current and voltage that make up the electromagnetic force, physicists at NIST, who are leading the project, use two different universal constants. One is the Josephson constant, while the other is the von Klitzing constant. It was the discovery of latter, part of the Quantum Hall Effect, that earned von Klitzing the 1985 Nobel Prize in Physics.

 

Five years earlier, von Klitzing, from the Max Planck Institute for Solid State Research in Germany, conducted experiments to observe the effect of magnetic fields applied to semiconductors that had been cooled to extremely low temperatures. He discovered that in his experiments the electrical resistance rose in a stepwise manner—an integer fraction of a specific number, 25,812.807 ohms, which is now called the von Klitzing constant.

 

The Quantum Hall Effect, as the phenomenon is called, is now used globally to calibrate electrical resistances. Scientists can use the von Klitzing constant to measure current in a watt balance.

 

"With the help of fundamental constants, we have the possibility of establishing units that necessarily retain their significance for all cultures, even unearthly and human ones," was a visionary statement of Max Planck more than 100 years ago and today we have the chance to realize this vision. The Quantum Hall Effect triggered this realization.

 

Von Klitzing will be in Singapore later this month to take part in the annual Global Young Scientists Summit. The five-day event, organised by the National Research Foundation Singapore, aims to facilitate interactions of bright, young international researchers with eminent scientists to discuss key areas of science and research, technology innovation and society, and solutions to global challenges.

 

Among the topics up for discussion is the kilogram's makeover. In November, members of the General Conference on Weights and Measures will gather in Versailles, France, to vote on the new definition for the kilogram, alongside that of the ampere, kelvin and mole. If approved, the updated and fixed values will come into effect from May 20, 2019, on World Metrology Day.

 

https://phys.org/news/2018-01-kilogram-makeover.html#nRlv

 

Ovo je pre dodavanja sedme i osme cifre Bolcmanu. 

 

WG22dQ0.jpg

 

"There are no dramatic changes. The Boltzmann constant is very consistent with earlier values," said Mohr. "The temperature experts requested eight digits for the constant and the last digit happened to be 0," he recounted—an amusing situation for metrologists since they can obtain the precision of eight significant digits by only having to use seven. :)

Read more at: https://phys.org/news/2017-10-scientists-key-fundamental-constants.html#jCp

Edited by bigvlada

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halloween

http://mentalfloss.com/article/50409/tycho-brahe-astronomer-drunken-moose

 

Quote

But perhaps the oddest aspect of Brahe's private life was his taste in pets. In 1591, Brahe's frequent correspondent Lantgrave Wilhelm asked about a mysterious animal he'd recently heard of called a "rix.” According to word of mouth, the creature was faster than a deer, but wielded shorter horns (or antlers).

In Brahe's response, he asked if Wilhelm had ever seen a live moose, for the astronomer just so happened to have once owned a tame one.

The hoofed critter would trot alongside Brahe's carriage like a loyal dog and lived inside his castle. But, unfortunately, it also appears to have developed a regrettable taste for Danish beer. Naturally, Brahe couldn't resist showing off such a bizarre young animal to his various associates and, soon enough, a nearby nobleman had asked him to send the moose to his castle to entertain the guests at a party.

As the dinner wore on, the creature grew increasingly tipsy until it eventually wound up roaring drunk. According to Brahe's biographer Pierre Gassendi, shortly thereafter, “the moose had ascended the castle stairs and drunk of the beer in such amounts that it had fallen down [them]” to its eventual demise.

 

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chandra
20 hours ago, Tsai said:

 

Zamisli da imas bilijarske kugle. Ako znas pocetne polozaje i pocetne brzine i mozes da izracunas polozaje i brzine u svakom sledecem trenutku. U klasicnoj mehanici nista te ne sprecava da obrnes strelu vremena: ako znas krajnje polozaje i brzine, mozes unazad da rekonstruises pocetni polozaj. Prosto gde god se vreme pojavi u jednacinama, ubacis minus ispred. 

 

E sad u dinamici fluida ili kompleksnih sistema to nije tako. Ako imas veliki broj kuglica (na primer, molekula) koje se sudaraju, posle nekog vremena njihove brzine i polozaji ce postici nekakvu ravnoteznu raspodelu cije srednje vrednosti karakterisu fluid. Iako bi u principu mogao da vratis svaku cesticu nazad njenom putanjom u pocetnu poziciju, taj proces je nemoguc je bi narusio drugi zakon termodinamike da entropija zatvorenog sistema uvek raste. To je prividno paradoks izmedju mikroskopske slike sveta (cestice) i makroskopske slike (fluid sastavljen od tih cestica). Objasnjenje paradoksa ne mogu lako da ti iznesem bez pripadajuce matematicke formulacije. 

 

To su procesi koji se mogu replicirati u kompjuterskim simulacijama. Ali i u simulacijama entropija takodje uvek raste jer imas razne difuzne procese koji su ireverzibilni. Ako ja dobro razumem, ovi likovi su uspeli da nekakvim algoritmom vrate simulirani sistem (sa mnogo "kuglica") unazad, tj. da iz krajnjeg resenja izracunaju pocetno. Mogu da zamislim razne primene takvog algoritma. Ono sto je bezveze to je taj pompezni naslov "obrnuli su strelu vremena", sto naravno niti su uradili, niti im je bila namera. 

 

 

 

 

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Bujodrag

Zla entropija

gadna kao škorpija.

I još gora.

Kosmička noćna mora.

Ona je neprijatelj jedini pravi

Sve nas postepeno muči i davi.

 

 

Smrt entropiji! uzvikivao bih snažno.

Al' džaba, smeje se. Ono što vičemo nije joj važno

:dry: 

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