Hello everybody! This video will tell you how to create an image to restore the system on Windows 10, that is, to create a complete system image with all its settings, applications, users, etc. As a result, you receive the conditional Windows 10, which existed at the time of creating a backup copy. With the help of this function, you can always get your system back to the previously saved condition. In order to create a Windows 10 system recovery image, go to the Start menu and click on Control Panel. Select the View Option large icons, then look for File History. In the next window, click on System Image Backup and create a system image. Then choose the location where this backup copy should be saved. It can be an external hard disk, a DVD, or a network folder. I'd like to note that you can create a Windows 10 recovery image on a flash drive only when this drive is recognized as a hard disk. Click Next. Select the disks to be backed up. By default, they are the System Disk, Disk Siege, and EFI System Partition. Click on Start Backup and the process of creating a Windows 10 backup copy starts. Sometimes it can take up quite a long time. When it is over, you will be suggested to create a recovery drive. If you don't have it and you don't have a boot disk or flash drive and even don't have access to another PC, where you could create them quickly, then I recommend creating such drive. As I already have one, I will not create such recovery drive. In my case, I click No and we can see a message that backup was successful. That is, a Windows 10 recovery image was created. In order to recover Windows 10 from a recovery image, you need to enter the system recovery environment. You can do it right from the system. You should go to Start menu, Settings, Update and Security, Recovery, and click on Restart Now in the section Advanced Startup. If Windows 10 won't boot, you can get to the system recovery environment with the help of a boot disk or a flash drive, where, after selecting your keyboard layout, you should click on System Restore. Or you can do it with the help of a recovery drive. You can see how to create a recovery drive and use it to enter Windows 10 recovery environment in my video resetting Windows 10, 8, 7 if your computer won't boot. I will show it with the example of a boot flash drive with Windows 10. Go to Bias or UFI, usually by pressing Delete for most PCs or F2 for most laptops. Set Boot Priority to let the computer boot from the USB drive. In my case, it is EFI USB device and Press Enter. In the next window, select the language we need. By default, it is English. Click Next and then System Recovery. Now click on Troubleshoot, Advanced Options, System Image Recovery and choose Windows 10 as the target system. Select Use the last available system image and click Next. After that, the recovery process will start. If you only created an image for Disk C and have not changed your partition structure ever since, there is no need to worry about the safety of your data on Disk D or other disks. When the process is over, set the boot sequence in BIOS so that the hard disk comes first and boot Windows 10 in the same condition as it was saved to a backup copy. Thank you for your attention and good luck. If you liked this video, click the Like button below and subscribe to our channel.


Hello and welcome to News Greek. Today we have with us Professor Satyajit Rath and we're going to discuss the explosion and literally it's an explosion of number of cases that we are seeing. Now in the United States, we already had seen this earlier in UK and in certain countries in Europe, France for example. We also try, we're also seeing similar explosions starting still very early stage but definitely starting in the metropolitan cities in India. Satyajit, we now have fairly clear view of which way this pandemic, this particular variant is going to go because I think certain numbers are very clear that it is going to displace Delta, it's going to be the dominant variant and the wave is going to be bigger than what we have seen in the past. This is what we seem to see in all countries. Of course the United States has crossed a million but that's because of the backlog of the holidays, probably the seven-day rolling average of 500,000 is probably a clearer picture but all the earlier waves have been crossed and we are starting to see also collapse of the hospitals that we saw and that we are seeing in Berlin for example. So broad picture that as we have been saying the denominator going up means ultimately the pressure in the hospitals will be there and yes we are now at the start of the Omicron wave in India as well. Well, yes with few reservations. In the first place as we have pointed out consistently for the past two years, countries should not really talk about waves. What we should be looking at is local outbreaks and the trajectories of local outbreaks and the outward spreads from local outbreaks. As you pointed out in India, the local transmission and outbreaks have been in the metropolitan areas, Mumbai, Delhi, now Bangalore, Kolkata are growing very, very rapidly in terms of case numbers. The second issue is many of us will remember last year. This was quite frequently said by anti-science skeptics of the COVID response that oh it's pretty much like influenza, why are we getting so worked up about it? And there were two responses to that. In the first place the frequency of severe illness was still clearly higher for influenza. And in the second place, the fact that for two years has been brought home to us repeatedly that if infection numbers explode in one week as the denominator, then even if a relatively small fraction of infected people become severely ill, the denominator number being large means that the numerator, meaning the people who land up in hospitals who overload their critical healthcare system not simply for COVID but for all other illnesses that are handled by the hospitals becomes a massive public health problem. And this is what happened last year with the early strains of COVID. What is happening with Omicron is the so-called good part which everybody is referring to calling oh it's just another mild viral fever as the chief minister of a popular state in the country has characterized it. Is that true? Yes, it seems to be true that the frequency of severe illness by Omicron is a little lower. But on the other hand, if transmissibility of Omicron is as high as it is showing every sign of being, then within a week, for example, case total infection numbers are so high that even a very small percentage of those landing up in hospitals is going to overload hospital systems. And that's what we are beginning to see steadily in the places that you point out and in many other places across the world. This is why again and again and again it is brought home to us that COVID-19 is not so much an individual risk where each one of us is an atomized terror for our lives as a collective risk that demands a societal, inclusive, collective, mutually supportive response. It's very important that you bring this out because in Maryland, for instance, we see the collapsed hospital system in Maryland may appear something that we don't know what the hell it is in the United States. It's actually in the region of New York, Washington DC, in that region in between the two is very much a part of the U.S. Capitol region densely populated, quite metropolitan as you would put it and therefore the hospital systems collapsing there and which is what we are seeing is also the consequence of the fact that number of patients come in but it's also the time when the public health people manning the public health system also forming. So you get the dual crisis that happens and they don't seem to have even drivers who can man the vehicles to bring patients to the hospital. So you really seeing a crisis of a dimension which we have seen earlier with the Delta variant and we thought that with Omicron being numbers being higher but cases being much lower, serious cases being much lower, we would not face the same crisis but this is untrue as Satyit points out that if the numbers explode as the way they are with Omicron then of course these numbers will also go up. So that's what we are beginning to see and I must remember that Professor Vijay Raghavan, Prime Minister's advisor had appeared when the public health system had got a bad name underestimating the second wave thinking they had won a victory being unprepared for what happened lack of oxygen and so on. He had been fielded to do some face saving and the midst of which he had talked about the inevitability of a third way after that we didn't hear him again. Maybe the government thought that was too frightening picture that he was painting but his prediction has really come true and that's something that we have always been thinking that yes whatever happens we are likely to get repeated waves. Of course Satyit doesn't like the word waves but rising now sharp rising numbers as he says spreading from cluster to cluster which the less informed will call waves. Now Satyit one other issue that that seems to be there is that the people who are not vaccinated and this is again what is coming from the hospital system in the US. The non-vaccinated and US you have this unfortunate picture of a large number of people who believe that vaccines are bad therefore they should not take it and they're not vaccinated out of not because of the lack of availability unlike say Africa parts of other parts of the world but simply because they do not believe that vaccines are good for them and apparently the numbers of those who are not vaccinated in the hospitals and particularly in serious cases has been multiple in fact one figure was 17 times that often the vaccinated people. Now I'm not going to take the 17 times as something within a very hard numerical figure but it does seem to indicate that those who are vaccinated tend to have much lower numbers of serious cases as a proportion as opposed to those who are not vaccinated. So the non-vaccinated figures for Delta Omicron may not be as significantly different as people think. Well is it is it true that the people who in the current rising number situation are landing up in hospitals are far more often the unvaccinated absolutely yes as you point out that has been seen in various places in the US but even in the United Kingdom amongst epidemiologist circles there seems to be a number being cited now I'm not I haven't seen the data so I'm sort of quoting a quote from Nick Ferguson but the number is 15% of people currently in hospital are vaccinated you have to see this on the background that in the UK 70% of people at large in the community are fully vaccinated and yet only 15% of people in hospitals are vaccinated. So you know you you actually begin to approach the 17 fold the number that you cited I agree entirely we shouldn't put too much of hard credence in these precise numbers but the evidence is quite consistent that just regular ordinary vaccination is providing significant protection against severe illness even from Omicron whether it provides 90% protection or whether it provides 70% protection is a separate issue but is it providing significant substantive protection yes it is and that is all the more reason for us to be provide to be taking vaccines to be demanding basic vaccinations and to be providing as states as governments as local authorities to be providing vaccination. Important issue here that in India for example we have vaccinated much better than lots of countries which are poor countries so in that sense we have done better but yet a significant part of the target population still remains unvaccinated not fully vaccinated not unvaccinated but not fully vaccinated and the people who are not vaccinated at all vaccinated at all are still not an insignificant number if you take India's population science that means we would still if just the unvaccinated people become seriously ill it could still collapse the hospital. Now given all this we should therefore think that we should really focus how the public health system can be geared up to cover those people who are not vaccinated target them and target the ones who have not received their second dose but even now what we see is talk about the children being vaccinated 15 to 18 booster doses being provided again the nine months gap is probably half the wave will be over before those who have had the second dose are even early second doses will even be eligible for booster doses but we don't seem to have the drive required to cover those who are not vaccinated or have not received the second dose. Well two issues here firstly whether we have the drive or not is almost rendered irrelevant by the apparent fact that we don't seem to have a special focused set of policies to address the problem of the unvaccinated all of us should remember that the unvaccinated are not simply random individuals distributed in communities the unvaccinated tend to cluster as communities as communities of the marginalized as communities of the underprivileged in places like the United States the communities of the irrational conservatives the irrational conservative radicals whatever you call them and all of these are communities in which the in which virus populations can grow enormously both in terms of rapidity as well as in terms of generating potential virus variants for future selection and so on and so forth so focusing on the unvaccinated and completing their second dose vaccination and where necessary first and second dose vaccination is going to take specifically designed policies whether you we have the drive or not we don't seem to have developed policies or at least they're not heard of in the public domain this is one major issue that I think across the world and particularly in India we are deficient the second issue connects to this point about communities remaining unvaccinated and when communities remain unvaccinated what we are doing by allowing communities on the one hand to remain unvaccinated and on the other hand creating hyperimmune communities these living cheek by job with booster doses is allowing a growing virus population with all the potential variants included in it to be repeatedly tested against the hyperimmune population so that future true immune escape variants acquire the likelihood of emerging in all these things however in all these terms therefore inclusive approaches are absolutely essential and what that means in vaccine terms is that we should not be in a situation where we are thinking about vaccinating on the ratings vaccinating with additional doses those at high risk such as healthcare professionals and completing the basic vaccination should not be either or situations our vaccine manufacture our vaccine supply our vaccine distribution and our vaccination implementation systems need to be geared to deliver all of these simultaneously it's worth asking if we are doing that that's I think the most important point that if we do not vaccinate everybody we are likely to see pockets of infections which will also create pertain ground for new variants to emerge which will be also what is called that will have vaccine escape and that is what Omicron is or has been that is also what we are likely to see if you have a picture of the world in which for instance Africa which has probably about six to eight percent of its people who have received two shots large parts of its population have not received even a single shot including the healthcare professions this is a context where it's important to underline Cuba everybody talks about not having enough vaccines not having enough resources not having this not having that Cuba has fully vaccinated more than 80% of its population including children with homegrown vaccines and the major major distinction is not that vaccines were invented or designed in public sector research organizations that is true the world over the major differences that Cuba provided public sector manufacturing seamlessly connected to vaccine development to make deliver and implement vaccination campaigns on scale this part of the lessons they've also shared this technology with other companies particularly in Latin America where other other players are now taking that up hopefully in other parts of the world as well I think that's a very important point that it is not simply a question of technology it's a really a question of will to do certain things and at the moment shortage of vaccines is not the issue shortage of will to really deliver vaccines to the people across the world this is the real real shortfall that we have which is creating again and again the chances of the pandemic lasting much longer we'll also talk about this and other issues particularly about what is being talked about endemicity what does endemic when the pandemic because becomes endemic what it means but that's for the next time thank you Satyit for being with us and discussing this and other issues with us and also sharing with our viewers what the pandemic is all about and what the likely scenario is going to be in the next few weeks is all the time we have for this click today do keep watching this click and do visit our website


Hello and welcome to the lecture on optical source laser learning outcomes by the end of the session student will be able to illustrate laser basic concept pause the video here and enlist the different optical sources three main optical light sources available are first is wideband continuous spectra sources that is incandescent lamp second is monochromatic incoherent source that is LED light emitting diodes and third is monochromatic coherent sources that is laser in this lecture we are going to concentrate on the basic concept of the third optical source that is laser what does laser stands for the optical source is often considered to be the active component in an optical fiber communication system its fundamental function is to convert electrical energy in the form of current into optical energy that is in the light energy in an efficient manner which allows the light output to be effectively launched or coupled into the optical fiber strictly speaking laser is a active device which amplifies light hence the derivation of the term laser as an acronym for light amplification by stimulated emission of radiations the operation of the device may be described by the formation of an electromagnetic standing wave within an optical cavity or resonator which provides an output of monochromatic highly coherent radiation which means laser is a narrow light beam of a single wavelength that is monochromatic in which each wave is in phase that is coherent with other waves laser is a device which produce an intense concentrated and highly parallel beam of coherent light to gain an understanding of light generating mechanism within the laser it is necessary to consider both the fundamentals of atomic concepts and the device structure is necessary atom consist of nucleus and electron if an interacting photon is energetic enough it may be absorbed by an atom rising to an excited state in 1917 it was pointed out by Einstein that an excited atom can return to a lowest state via two distinctive mechanisms those mechanisms are first is spontaneous emission and second is stimulated emission figure number one illustrate two energy level atomic system where an atom is initially in lower energy state when a photon with enough energy that is band gap energy is incident on an atom it may be excited into higher energy state through the absorption of the photon this process is sometime referred to as stimulated absorption alternately when an atom is initially in the higher energy state it can make a transition to the lower energy state providing the emission of a photon this emission process can occur in two waves by spontaneous emission or by stimulated emission we will see the spontaneous emission first the spontaneous emission process is illustrated in the figure number two which shows an electron in excited state an excited state electron releasing photon during transition from higher state to the lower state in spontaneous emission the atom returns to the lower energy state from higher energy state or excited state in an entirely random manner this random nature of spontaneous emission process where light is emitted by electromagnetic by electronic transitions from a large number of atoms giving incoherent radiation that is each wave has a different phase with the other waves each similar emission process in semiconductor provides the basic mechanism for light generation within the LED which is also an optical source stimulated emission in stimulated emission when a photon having an energy equal to the energy difference between the stood state interacts with the atom in the upper energy state causing it to return to the lower state with the creation of a second photon which is shown in figure number three the photon produced by stimulated emission is generally an identical energy to the one which caused it and hence the light associated with them is of the same frequency the light associated with the stimulating and stimulated photon is in phase and has same polarization therefore in contrast to the spontaneous emission coherent radiation is obtained furthermore this means that when an atom is stimulated to the light energy emission by an incident wave the liberated energy can add to the wave in a constructive manner providing amplification population inversion under the condition of thermal equilibrium the lower energy level of the two level atomic system contains more atoms in than the upper energy level this situation which is normal for structures at room temperature however to achieve optical amplification it is necessary to create a non-equilibrium distribution of atoms such that the population of the upper energy level is greater than that of the lower energy level this condition is known as population inversion this process is achieved using an external energy source and that energy source is referred as pump in order to achieve population inversion it is necessary to extract atoms into the upper energy level and hence obtain a non-equilibrium distribution the two level system discussed above does not lend itself to a suitable population inversion the population inversion however may be obtained in a systems with three or four energy levels the three energy level diagrams for such systems is shown in figure number four to aid attainment of the population inversion system display a central metastable state in which the atoms spend an unusually long time in orders of millisecond to seconds the three level system shown in figure number four consists of a ground level even a metastable level e2 and a third level above the metastable level is e3 which suitable pumping the electrons in some of the atoms may be excited from the ground level even into the higher level e3 since e3 is a normal level the electrons will rapidly decay by non-radiative process to either e2 or directly to the even level the metastable level even exhibits a much longer lifetime than level e3 which allows a large number of atoms to accumulate at level even over a period the density of the atoms in the metastable state increases above those in the ground state and a population inversion is obtained between these two levels stimulated emission and hence lasing can then occur creating a radiative electron transition between levels e2 and even to generate laser beam three conditions must be satisfied that is first stage population inversion stimulated emission and third is pumping of atoms from lower energy state to higher energy level the light amplification in laser occurs when a photon colliding with an atom in the excited energy state causes the stimulated emission of second photon and then both these photons release two more continuation of this process effectively creates creates avalanche multiplication and when the electromagnetic waves associated with these photons are in phase amplified coherent emission is obtained to achieve laser action it is necessary to contain photons within the laser beam and maintain the condition for coherence this is accomplished by placing plane or curved mirrors at either end of the amplifying medium as shown in figure number five the optical cavity formed is more analogous to an oscillator than an amplifier as it provides positive feedback of the photons by reflection at the mirrors hence the optical signal is fed back many times while receiving amplification as it passes through the medium the structure acts as a fabric aerotraisonator although the amplification of the signal from a single pass through the medium is quite small but after multiple passes the net gain can be large and lasing takes place the types of pumping source the optical pumping source this pumping method is suitable for liquid and solid laser because they have wide absorption bands the second is electric pumping this pumping method is suitable for gas laser because they have narrow absorption band and the third is pumping through chemical reaction these pumping sources are used to achieve population inversion the types of laser laser classification is based on the type of laser active medium the three types are solid liquid and gas in solid laser ruby is an example and aluminum granite in liquid laser dyes are there in gas lasers helium neon organ or carbon dioxide these are the some of the examples of laser materials these are the references thank you