How does an hourglass measure time?
The sand timer hourglass is sometimes referred to as a sand clock or a sandglass. Like other timepieces, it needs to be carefully calibrated. The hourglass maker must test the instrument and fine tune it to measure the correct length of time.
There are many factors that contribute to the ability of an hourglass to accurately measure time. The type and quality of sand is key. It must have a rate of flow that does not fluctuate. Sand that is too coarse will wear away the glass, eventually making the neck too large. Most important is the ratio of the neck (the hole, or tube) width to the diameter of the sand particles.
Here are the other factors that affect the accuracy of an hourglass:
The amount or volume of sand used
The size and angle of the glass bulbs
The quality of the sand or granular material. It must be fine, dry and consistently formed so it can flow smoothly. (Some substances used in the past were fine grain sand, powdered eggshells, and powdered marble.)
The width of the neck
A tight seal so no moisture can get into the chambers. Moisture can add weight to the sand or clog up the neck.
A flat and level surface on which to rest the hourglass
Like a foam roller, a massage ball can also be used to help release tension in our achy muscles after long hours spent in the office or after a workout. One of the differences being that it can get to those hard to reach areas such as the upper back, buttocks and feet. “Knots” or “trigger points” can be massive sources of pain in our bodies and using self-massage techniques can be very satisfying. Before diving in, there are a few important things to know which will help you achieve the best results.
Why a massage ball
Massage balls are affordable and small and therefore they can easily fit into a suitcase or handbag to use wherever you go. They also promote self-sufficiency so there is no need to rely on anyone else. Notwithstanding, it does not always give the same results as a traditional massage delivered by an experienced therapist
Find the right ball
There are many different types of massage balls ranging from very smooth and firm like a lacrosse ball to small and soft like a squash ball. Other balls include a tennis ball and the trusty spikey massage ball. To each his own but if you’re new to using a massage ball, perhaps start with a spikey ball or a tennis ball.
Where and when
Since they are so conveniently easy to use, you can use them almost anywhere for example against a wall, the back of a chair, on the floor or use your hands. Some office workers keep them at their desks as a reminder to use them during the day to help with releasing built-up muscle tension from poor posture or stress.
Start with only a few knots at a time, the most painful area being first. The idea is to trap the knot in the muscle with the ball and apply gently to medium pressure until the painful sensation has faded. Once you have the correct spot (and you will know when), hold it there and try to relax until only about 80% of the ache remains. When pressing too firmly, the sensation can be too painful for you to relax which defeats the purpose of using the massage ball in the first place, it could also potentially irritate the area. You are looking for a “good pain”.Roll the ball around to look for more tender spots or just enjoy gently going back and forth over the tight muscle. If you feel the muscle needs it, you can repeat it twice a day. After releasing the knot, follow it up with gentle stretches to the same muscle. It’s okay to lightly exercise the muscle afterward but avoid fatiguing it for 24 hours.
“The Crown Jewels for Collectors” — that’s what Paul Hollister wrote about fine glass paperweights. He was one of the foremost scholars of 17th to 19th century glass studies, glass paperweights, and contemporary studio art glass. Paperweights are considered the most collectable of 19th century glass items, and also the most challenging of the glass arts to make. Fine glass paperweights are, indeed, rare treasures.
Most antique paperweights of quality were made by one of three French factories, as a sideline, for just 10-15 years in the mid-1800s. It’s estimated that only about 25,000-30,000 remain today, with many tightly held in museum collections. Fine contemporary paperweights are made by a limited number of studio artists and are sold either by the artist, or by a small group of specialty dealers.
The mid-to-late 1800s were sentimental and romantic times, heralded by an emerging middle class, resulting from the matured Industrial Revolution. Letter writing became a fad, and paperweights were sold in stationery stores as an attractive accessory to desk-sets of pens, inkwells, blotters, and fine stationery. The first glass paperweight was made in 1845 by Venetian glassmakers in response to the letter-writing fad. They could have been made 300 years earlier because the techniques were known, but paper was then a rare commodity and there was no need for a paperweight. They are the perfect example of form following function.
American made paperweights followed from 1851 into the late1880s, by the Boston and Sandwich Glass Company, and the New England Glass Company — and more rarely by makers including Dorflinger, Mount Washington, Gillinder, and Whithall Tatum companies. Their glassmakers were mainly European immigrants already skilled in the craft, which explains why American weights are somewhat imitative of the European. What American weights may have lacked in quality, they more than made up for in creativity and ingenuity, which makes them even more charming to their collectors.
What does iCloud Keychain do?
When you enter a new password in Safari, you’ve probably seen iCloud Keychain ask if you would like it to save it for use across all your devices. So long as you are running iOS 7.0.3 or later or OS X Mavericks 10.9 or later, iCloud Keychain will store the following items securely in iCloud. Once secured in iCloud Keychain, you will be able to access all these items securely from any Apple system logged into your Apple ID.
Safari website usernames and passwords
Credit card information
Wi-Fi network information
Ensure Mail, Contacts, Calendar and Messages are synced across all your devices
Protect, access and deploy your LinkedIn, Twitter and other Internet account logins and passwords.
How does iCloud Keychain work?
iCloud Keychain must be enabled on each device. Devices that are not enabled for the service will not be able to access the information it holds, so you’ll need to enter your passwords and other details manually.
How do I use iCloud Keychain in Safari?
When registering for a new website or service you will be asked to enter your information in the site’s registration fields. iCloud will populate these fields with things such as your name and telephone number. You will also be asked to create a password by entering your new password in the password field and the password confirmation field. When you tap your cursor in the first of these fields you will see a small item appear, tap this to use an iCloud supplied password. In practice, if you use your own password or one supplied by iCloud, it should be stored for later use by your iCloud Keychain.
How do I add credit card details to iCloud Keychain?
You can also add your credit card details to iCloud Keychain. You can choose to follow on-screen prompts to do so automatically as and when they appear, or enter these details manually as follows:
On a Mac: Open Safari’s AutoFill item in Preferences. Look for the Credit Cards item and tap Edit. In the next screen, you will be able to add and delete new cards. Tap Done.
On iOS: In Settings, open Safari>Autofill. Here you can choose to enable or disable Autofill of names and passwords, and as well as control what credit card information is held. Tap Saved Credit Cards, and you will be able to add or delete your stored credit card information. Tap Done.
The fabrication of the early spherical shells was limited to free forming of small hemispheres from thin acrylic sheets by compressed air. But even with all the limitations, the ocean engineering community saw the advantages acrylic offered to panoramic visibility.
Actual diving systems with the all-acrylic pressure hulls which demonstrated this potential were HIKINO, KUMUKAHI, and NUCOTE.
HIKINO was conceived in 1962 by the late Dr. William McLean and engineered by D.K. Moore of NOTS, China Lake. The two-person vehicle had the shape of a catamaran with the acrylic sphere suspended between the two hulls. The acrylic sphere itself was assembled from two free-formed hemispheres mated at the equator to a metallic joint ring.
The vehicle successfully demonstrated the design concept of panoramic visibility but because it was free formed from thin commercially available sheets, the design depth was only 20 feet. As a result of this severe limitation, it was subsequently used only as a concept demonstrator in a shallow swimming pool.
KUMUKAHI was conceived in 1967 by T.A. Pryor, engineered by Will Forman, fabricated by Fortin Plastics, and delivered to Oceanic Institute in Hawaii in September 1969. The submersible was configured as a self-propelled diving bell with the batteries and a variable displacement tank contained in a pod suspended directly under the sphere.
- Creado: 22-02-22
- Última sesión: 22-02-22