![]() What is the difference between the behavior of sound waves and light waves in this case? The answer is that light has very short wavelengths and acts like a ray. ![]() When sound passes through a door, we expect to hear it everywhere in the room and, thus, expect that sound spreads out when passing through such an opening (see Figure 27.8). What happens when a wave passes through an opening, such as light shining through an open door into a dark room? For light, we expect to see a sharp shadow of the doorway on the floor of the room, and we expect no light to bend around corners into other parts of the room. The ray bends toward the perpendicular, since the wavelets have a lower speed in the second medium. Snell’s law can be derived from the geometry in Figure 27.7, but this is left as an exercise for ambitious readers.įigure 27.7 Huygens’s principle applied to a straight wavefront traveling from one medium to another where its speed is less. This explains why a ray changes direction to become closer to the perpendicular when light slows down. Since the speed of light is smaller in the second medium, the waves do not travel as far in a given time, and the new wavefront changes direction as shown. Each wavelet in the figure was emitted when the wavefront crossed the interface between the media. The law of refraction can be explained by applying Huygens’s principle to a wavefront passing from one medium to another (see Figure 27.7). The direction of propagation is perpendicular to the wavefront, as shown by the downward-pointing arrows. The tangent to these wavelets shows that the new wavefront has been reflected at an angle equal to the incident angle. The wavelets shown were emitted as each point on the wavefront struck the mirror. In addition, we will see that Huygens’s principle tells us how and where light rays interfere.įigure 27.6 Huygens’s principle applied to a straight wavefront striking a mirror. We will find it useful not only in describing how light waves propagate, but also in explaining the laws of reflection and refraction. Huygens’s principle works for all types of waves, including water waves, sound waves, and light waves. The new wavefront is a line tangent to the wavelets and is where we would expect the wave to be a time t t later. These are drawn at a time t t later, so that they have moved a distance s = vt s = vt. Each point on the wavefront emits a semicircular wave that moves at the propagation speed v v. A wavefront is the long edge that moves, for example, the crest or the trough. ![]() The new wavefront is a line tangent to all of the wavelets.įigure 27.5 shows how Huygens’s principle is applied. Starting from some known position, Huygens’s principle states that:Įvery point on a wavefront is a source of wavelets that spread out in the forward direction at the same speed as the wave itself. The Dutch scientist Christiaan Huygens (1629–1695) developed a useful technique for determining in detail how and where waves propagate. The direction of propagation is perpendicular to the wavefronts (or wave crests) and is represented by an arrow like a ray. Figure 27.4 A transverse wave, such as an electromagnetic wave like light, as viewed from above and from the side.
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![]() Enrollment Back side of the physical Apple Card showing the Goldman Sachs and Mastercard logos Instant issuance The Wall Street Journal reported in June 2023 that Goldman Sachs had entered into discussions with American Express to explore the possibility that American Express might take over the partnership, replacing Goldman. On April 17, 2023, Apple began offering a high-yield savings account backed by Goldman Sachs to Apple Card users. In January 2023, Bloomberg reported that Goldman Sachs suffered $1 billion in losses because of the card. Up to five individuals may be additional cardholders or co-owners. Individuals 18 years and older can be co-owners of the account, while individuals 13 years and older can be additional cardholders. These features have been introduced under the brand Apple Card Family. On April 20, 2021, Apple announced that it would be introducing joint accounts and additional cardholders. Other services announced at the event include Apple TV+, Apple News+, and Apple Arcade. Unlike previous special events which have historically served as platforms to announce upcoming hardware, this event focused on new internet software and services. ![]() Goldman Sachs defended the terms of the deal saying they were "thrilled" with the partnership and seeking "to disrupt consumer finance by putting the customer first." Īpple Card was announced at an Apple Special Event on March 25, 2019. These features are seen as being risky for a bank to take on, and led other banks with established consumer credit card operations including Apple's long time partner Barclays, along with Citigroup, JPMorgan Chase and Synchrony, to turn down Apple's proposal. The card features a number of consumer-friendly features including no fees, software that encourages users to avoid debt or pay it down quickly, the industry’s lowest interest rate range for comparable cards, and a mandate to approve as many iPhone users as possible. Additional cardholders and joint accounts were not supported at its launch. It was released in the United States on August 20, 2019. On August 6, 2019, invitations to an early preview started being sent to randomly selected users who had previously signed up for email notifications ahead of Apple Card's official launch. Currently, it is available only in the United States, with 6.7 million American cardholders in early 2022. and issued by Goldman Sachs, designed primarily to be used with Apple Pay on an Apple device such as an iPhone, iPad, Apple Watch, or Mac. Apple Card is a credit card created by Apple Inc. Not much longer after that, televisions started coming with DVD or VCR players built directly into the base. After some time, the combination DVD and VCR player became an option. The combination of two different pieces of equipment is nothing new for technology and has long been the natural progression of equipment.įor example, televisions used to require a separate DVD player or VCR in order to play videos. For the sake of convenience, it’s becoming more common for people to use gateways instead of using a router and a modem separately. In fact, it’s so common that they actually have a term for it: gateway. When considering a router, you shouldn’t overlook this highly important feature.Īlthough they are performing two different functions, it’s fairly common for a modem and router to be bundled together into one piece of equipment. Most routers will come with a firewall or some degree of basic protection, but there are a few security features that truly excel at keeping your information safe. The modem generally only acts as commanded, downloading and uploading data based upon the prompts and requests that your devices make.Īs a result, there can often be viruses, malware, and other cyber-related threats that sneak their way into your network. ![]() Another often underrated responsibility of the router is to act as the first line of defense against cyber attacks. When your device connects to the router, it will then be able to upload and download data information from the internet through the modem. Instead, they connect to the modem and rely on that connection to reach the internet.Ī router is responsible for creating a Wi-Fi personal network that connects to all of your various devices. Contrary to popular belief, routers do not connect directly to the internet. However, you won’t be able to use Wi-Fi and will most likely only be able to use one device online at a time. Technically, you don’t need a router in order to connect to the internet. Since modems can usually only connect to one other device at a time, this is where the router will enter into the process. One of the ports will connect to the internet via a coaxial cable or other similar wire while the other will use an ethernet cable to connect directly to a computer or the router. Most modems will only have two ports with two different purposes. They are responsible for taking these complex electrical signals and breaking them down into universal analog signals that can easily be read by your personal computer, phone, television, tablet, or whatever other device you are using. Modems get their name from their ability to “modulate” and “demodulate” the electrical signals that make up the internet. The role of a modem is to connect directly to the internet by using the cables provided by your internet service provider. ![]() Before you make any decisions on which path to go down, you should first learn a little bit about what each piece of equipment does. While these pieces of hardware are typically sold separately and with plenty of incredible features available, they are sometimes packaged together into one unit. ![]() Unless you already have the necessary equipment, you will need to acquire a modem and a router. After you have made your choice, there are still some decisions left to be made. ![]() There are plenty of decisions that you will have to make in terms of which internet service provider to use and the best overall subscription package for your needs. It can be quite a long process whenever you are trying to set up an internet connection in your home. 4 3 Although HHV-6A is rare in the general population, HHV-6A and HHV-6B are encountered in approximately one-third and two-thirds of individuals with CIHHV-6, respectively. ![]() Chromosomally integrated human herpesvirus 6Īs well as the almost universal postnatal acquisition of HHV-6B, in approximately 1% of humans the complete genome of HHV-6A or HHV-6B is integrated into a chromosomal telomere in every nucleated cell in the body and is transmitted through Mendelian inheritance. In contrast, HHV-6B primary infection is ubiquitous in the first two years of life sometimes causing exanthema subitum subsequent viral latency gives the potential for reactivation and disease. 2 No disease has been causally linked to HHV-6A, and its natural history is unknown. The two species of HHV-6, HHV-6A and HHV-6B infect and establish latency in different cell types including CD4 positive T lymphocytes, monocytes, and other epithelial, fibroblastic and neuronal cells. Human herpesvirus 6A and human herpesvirus 6B European Society of Clinical Microbiology and Infectious Diseases (ESCMID) grading system. (A list of ECIL meeting participants is provided in the Online Supplementary Appendix.) A final slide set was posted on the ECIL website ( on Octoand made available for open consultation. Those guidelines specifically applying to treatment were graded according to pre-ordained criteria ( Table 1) for level of evidence and strength of recommendation participants were hematologists, microbiologists and infectious disease specialists with expertise on infectious complications in hematology. ![]() Revised European Conference on Infections in Leukemia (ECIL) HHV-6 guidelines were prepared after a literature review by a group of experts, and discussed at a plenary session on Septemuntil consensus. Over the past ten years, it has been recognized that human herpesvirus 6A (HHV-6A) and HHV-6B are distinct species, 1 HHV-6B not HHV-6A is the most frequent cause of encephalitis post-hematopoietic stem cell transplant (HSCT) and that chromosomally integrated HHV-6 (CIHHV-6) is clinically significant. Revised guidelines prepared at the 2017 European Conference on Infections in Leukaemia covering diagnosis, preventative strategies and management of HHV-6 disease are now presented. Guidelines for the management of HHV-6 infections in patients with hematologic malignancies or post-transplant were prepared a decade ago but there have been no other guidelines since then despite significant advances in the understanding of HHV-6 encephalitis, its therapy, and other aspects of HHV-6 disease in this patient population. Notes: The current error page you are seeing can be replaced by a custom error page by modifying the "defaultRedirect" attribute of the application's configuration tag to point to a custom error page URL.Of the two human herpesvirus 6 (HHV-6) species, human herpesvirus 6B (HHV-6B) encephalitis is an important cause of morbidity and mortality after allogeneic hematopoietic stem cell transplant. This tag should then have its "mode" attribute set to "Off". It could, however, be viewed by browsers running on the local server machine.ĭetails: To enable the details of this specific error message to be viewable on remote machines, please create a tag within a "web.config" configuration file located in the root directory of the current web application. ![]() The current custom error settings for this application prevent the details of the application error from being viewed remotely (for security reasons). Runtime Error Description: An application error occurred on the server. Runtime Error Server Error in '/' Application. ![]() ![]() Source: British data from Great Britain, General Report. (Fatality rates per Thousand Workers per Year) Years 5īritish and American Mine Safety, 1890 -1904 For such reasons, American methods yielded more coal per worker than did European techniques, but they were far more dangerous, and toward the end of the nineteenth century, the dangers worsened (see Table 1). Miners themselves were by no means blameless most were paid by the ton, and when safety interfered with production, safety often took a back seat. Since miners worked in separate rooms, labor supervision was difficult and much blasting was required to bring down the coal. Such methods used coal pillars and timber to hold up the roof, because timber and coal were cheap. American coal deposits by contrast, were both vast and near the surface they could be tapped cheaply using techniques known as “room and pillar” mining. British methods also concentrated the working, making supervision easy, and required little blasting. As a result, British mines used mining methods that recovered nearly all of the coal because they used waste rock to hold up the roof. In Britain, coal seams were deep and coal expensive. Nowhere was the American system more dangerous than in early mining. Because accidents were so cheap, American industrial methods developed with little reference to their safety. A number or surveys taken about 1900 showed that only about half of all workers fatally injured recovered anything and their average compensation only amounted to about half a year’s pay. Where employers could show that the worker had assumed the risk, or had been injured by the actions of a fellow employee, or had himself been partly at fault, courts would usually deny liability. ![]() While workers injured on the job or their heirs might sue employers for damages, winning proved difficult. As a result, Americans developed production methods that were both highly productive and often very dangerous. These developments occurred within a legal and regulatory climate that diminished employer’s interest in safety. Reflecting the high wages and vast natural resources of a new continent, this American system encouraged use of labor saving machines and processes. US Was Unusually DangerousĪmericans modified the path of industrialization that had been pioneered in Britain to fit the particular geographic and economic circumstances of the American continent. What is clear is that nowhere was the new work associated with the industrial revolution more dangerous than in America. But whether these new technologies generally worsened the dangers of work is unclear. Industrialization substituted steam engines for animals, machines for hand tools, and elevators for ladders. Pre-industrial laborers faced risks from animals and hand tools, ladders and stairs. As a result, only fragmentary information exists prior to the 1880s. 2 The Nineteenth Centuryīefore the late nineteenth century we know little about the safety of American workplaces because contemporaries cared little about it. A century ago in 1900 about three hundred out of every one hundred thousand miners were killed on the job each year. ![]() Its annual fatality rate is about nine for every one hundred thousand miners employed. To take but one example, mining today remains a comparatively risky activity. But even the dangerous trades are now far safer than they were in 1900. In part this has been the result of the gradual shift of jobs from relatively dangerous goods production such as farming, fishing, logging, mining, and manufacturing into such comparatively safe work as retail trade and services. 1 Over the past century such measures reveal a striking improvement in the safety of work in all the advanced countries. The dangers of work are usually measured by the number of injuries or fatalities occurring to a group of workers, usually over a period of one year. History of Workplace Safety in the United States, 1880-1970 ![]() Iron contributes to normal formation of red blood cells and haemoglobin and normal oxygen transport in the body.With specific nutrients which contribute to: Reduction of Tiredness & Fatigue (folate) Normal Formation of Red Blood Cells & Haemoglobin (Iron)įor allergens, including Cereals containing Gluten, see ingredients in bold. Feroglobin's specific blood building nutrients may be of particular benefit for athletes, and for women during the monthly cycle and throughout pregnancy. This special formula also contains vitamin C which increases iron absorption, vitamins B6 & B12 which contribute to normal energy release, plus iron and folate which contribute to the reduction of tiredness and fatigue. ![]() ![]() Feroglobin® Liquid is a unique gentle liquid iron formula with nutrients to help maintain health and vitality. Vegetarian Society Approved.Gentle iron natural source* Gentle iron to help support your haemoglobin and red blood cells *The form of iron used in Feroglobin Liquid is produced from a natural source of iron. Delicious taste with natural orange extract, honey and Swiss Alpine malt. Suitable for both adults & children over 3 years. Feroglobin liquid is not tested on animals. Plus contributes to normal formation of haemoglobin & red blood cells. Iron contributes to reduction of tiredness & fatigue. Liquid food supplement with iron, zinc & B vitamins in a blend of malt and honey 14 minerals & nutrients. |
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