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The Engineer's Notebook

The Engineer's Notebook is a shared blog for entries that don't fit into a specific CR4 blog. Topics may range from grammar to physics and could be research or or an individual's thoughts - like you'd jot down in a well-used notebook.

The Latest Tech for Sharkproofing Beaches

Posted June 20, 2016 11:04 AM by Jonathan Fuller
Pathfinder Tags: shark attacks sharks

Next month marks 100 years since the Jersey Shore shark attacks. A rogue shark (or multiple sharks, depending on which scientist you ask) killed four people and injured one during a two week span in early July 1916, at a time when a brutal heat wave and polio epidemic were driving thousands to resorts on the Atlantic coast. The attacks not only spurred panic and shark eradications on a national scale, they also immediately redefined the shark’s image from one of a timid sea creature to “the incarnation of ferocity.” Shark fever swept the nation, and soon newspaper cartoonists were using sharks to lampoon topics as diverse as German U-boats and prudish Victorian bathing suits.

Today, of course, ichthyologists know the truth about sharks and their behavior: they have lots of sharp teeth and occasionally attack without provocation. The popularity of films like Jaws and the annual sharkathon Shark Week, which kicks off June 25th this year, confirms that the mystique is still in vogue a century after the New Jersey incidents. While fatal shark attacks draw heavy media attention, they’re quite rare, with less than 100 total attacks reported each year. Still, those with a stake in beaches and resorts use a variety of technologies to prevent attacks.

A simple strategy for preventing attacks is to detect a shark’s presence and warn beachgoers to get the heck out of the water. In Cape Cod, Massachusetts, where a burgeoning seal population is drawing record numbers of great whites closer to shore, municipalities are posting traditional signage as well as large, dramatic billboards showing scary-looking sharks. For people whose heads are permanently looking down at their phones even at the beach, local group Atlantic Great White Conservancy is launching an app to allow visitors to track tagged great whites or quickly report seeing untagged ones. This year Cape Cod and other locales on the Eastern Seaboard may begin using drones to monitor shark populations close to shore. California and Australia already engage in drone monitoring, but the murky East Coast waters make visual sightings a challenge.

The other angle is to repel sharks from heavily populated beaches altogether. Traditionally, drum lines and shark nets were used for this purpose, but these methods endanger other non-harmful species, including non-aggressive sharks. South Africa’s KwaZulu Sharks Board is currently commercializing a shark-deterrent cable they tested in 2014. The cable features vertical “risers” that emit a low-frequency signal designed to confuse the shark’s sensory system. A shark’s nose contains an electroreceptive organ called the ampullae of Lorenzini that detects the potential difference between the voltage at the base of the electroreceptor and the voltage at the shark’s skin. The ampullae allow the shark to detect a far-off living creature’s heartbeat through the water, assisting with hunting and tracking. If successful the cable would be a huge improvement over shark nets: sharks have the greatest electrical sensitivity of any known animal, so the small electric fields won’t bother any other sea life or nearby humans. According to the Shark Board, the cable’s current is so small that a person accidentally contacting the cable would feel little more than a tingle.

Shark attacks are rare, but as evidenced by the recent Orlando alligator incident, most vacationers aren’t attuned to keeping their eyes peeled for local wildlife hazards. Development of sharkproof tech seems to benefit all involved, from the beachside communities who lose business at the first sign of a fin to the tourists who depend of them to stay safe.

Image credit: KwaZulu Natal Sharks Board

1 comments; last comment on 06/20/2016
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Coral Bleaching

Posted June 03, 2016 12:07 PM by BestInShow
Pathfinder Tags: bermuda coral bleaching sunscreen

Snorkeling along part of Bermuda's coral reef was one of the highlights of my recent trip to the island. Given the dire state of corals around the world, spending a little time amongst robustly healthy corals, and the resident fish, was a pleasure and a privilege. Why is Bermuda's reef in such good shape? Why are others, from the Great Barrier Reef to locations in the Florida Keys, dying? What, if anything, can we do to save what's left? Big questions, and articles abound that describe problems and potential solutions.

Rather than regurgitate a summary of the plethora of virtual ink dedicated to coral, I'll look at one less-obvious stressor of coral ecosystems. I'll also look at some ideas for coral restoration and ways to prevent further damage.

Coral Bleaching: Symptom of Stress

This year's El Nino event sparked the biggest coral die-off since 1998's El Nino. Pictures of swaths of bleached Great Barrier reef coral - estimated at one-third of the entire reef - show up with dismaying frequency. A number of news outlets published stories as I was writing this post. This phenomenon occurs when stressed corals expel the algae, called zooxanthellae, that live symbiotically within coral tissues. The algae are the coral animal's major food source, as well as the source of its color. NOAA's infographic below demonstrates this process. Soft corals are particularly prone to bleaching.

Infographic: NOAA

Stressors: Obvious and Not-So-Obvious

Those of you who are reading this can undoubtedly list some obvious anthropogenic environmental stressors.

  • Global warming and increased ocean temperature
  • Changes in ocean water chemistry - salinity levels and acidity
  • Pollution from waste runoff
  • Heat pollution from power plant cooling water discharge
  • Overexposure to humans via recreational scuba diving
  • Overfishing and use of destructive fishing methods
  • Loss of fish which clean seaweed from reefs

An additional and more subtle culprit is the chemicals in most sunscreens. The oldest research I found in a cursory web search is an from Environmental Health Perspectives published in 2008, "Sunscreens Cause Coral Bleaching by Promoting Viral Infections." The role of sunscreen hasn't gotten much attention until this latest episode of massive bleach-outs, though. At the time of publication, the authors estimated that 4,000 to 6,000 metric tons of sunscreen washes off swimmers in oceans worldwide. The more swimmers and divers cluster around reefs, the higher the concentration of washed-off Coppertone. And even a vanishingly small amount of the bad stuff can wreak havoc. Ironic that the stuff that protects humans from sunburn and skin damage helps cause coral to lose color and die.

The sunscreen chemicals that cause damage are paraben, a preservative; cinnamate and a camphor derivative, UVB blockers; and benzophenone, a UVA blocker. These chemicals do their dirty work by causing dormant viruses in coral's symbiotic algae

to wake up and replicate, eventually causing the algae to explode. The explosion propels the viruses into surrounding seawater where they can infect other corals. There is also evidence that chemicals alter the DNA of juvenile coral polyps, causing deformities and unviability.

Sunscreens with non-chemical UV blockers don't harm coral - at least, as far as we know today. These non-chemical blockers are our old friends zinc oxide, the stuff lifeguards paint on their noses, and titanium dioxide. Together these provide broad spectrum protection. A lot of websites advertise reef-safe and reef-friendly sunscreens and sunblocks.

An Aside about European Sunscreens

Recently I'd read that European and Australian scientists have access to much more effective sunblocking chemicals that are unavailable to those of us in the US. The story of why they are unavailable, despite 20 years' worth of user data demonstrating their safety and effectiveness, is too long for this post. Suffice it to say that testing takes money, either from the FDA or the product manufacturer, and evidently no one's interested enough to pony up.

I wondered if these FDA-banned ingredients are safer for coral than the three UV blockers listed above. I was thinking hey, not only are US citizens unnecessarily deprived of more effective sunscreens, we're also killing coral. Sure enough, as far as we know, none of the ingredients listed below harm coral or humans, at least not European and Australian humans. To add a touch of irony, a factory in South Carolina manufactures sunscreen with banned ingredients and ships it all to Europe.

  • Tinosorb M (UVA blocker)
  • Mexoryl XL (UVA blocker; SX available in the US but less effective)
  • Uvinul T 150
  • Uvinul A Plus
  • Uvasorb HEB
  • Parsol SLX

Coral Preservation and Growth

Stressed coral dies quickly and in large quantities. However, coral reefs grow agonizingly slowly. Large corals, like brain corals, grow 0.3 to 2 centimeters per year; soft corals, up to 10 centimeters a year. At this rate, a reef takes 10,000 years to form. A large barrier reef or an atoll can take 100,000 to 30 million years to form. Given this timeframe, preservation efforts are far more important than attempts to create new reefs, although there are ongoing efforts to provide structures, like sunken ships, for coral polyps to latch onto. Mr. Best in Show and I saw coral starting to grow on a shipwreck on our snorkeling trip; Bermuda has plenty of wrecked ships, most or all of which ran afoul of the reef.

Individuals can help keep coral healthy by using the right sunscreen and by refraining from touching coral when snorkeling or SCUBA-ing. Creating marine preserves where harmful activities are banned and human access is regulated is mandatory. Bermuda's government has passed laws to protect the island's reefs since the 1600s; this protection is one key factor in Bermuda reef health. Each of the factors leading to reef death can be addressed if enough political and ecological interest exist. For example, restoring populations of reef-cleaning fish directly improves reef health. Diligent monitoring programs, such as those managed by the Bermuda Reef Ecosystem Analysis and Monitoring (BREAM), discover potential threats and can avert significant damage - at least, that's what we hope. Global warming and carbon dioxide levels have already killed irreplaceable swaths of coral world-wide; what the future holds, we can't know.


Image credits



4 comments; last comment on 06/08/2016
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Are You A Workaholic?

Posted June 01, 2016 12:00 AM by Chelsey H

Are you a workaholic? Do you brag about it? Or are you trying to stop?

A study of 16,426 working adults in Norway studied the association between workaholism and psychiatric disorders, specifically ADHD, OCD, anxiety, and depression. Image credit

The study defined seven criteria when identifying addictive behavior. They are:

  • You think of how you can free up more time to work.
  • You spend much more time working than initially intended.
  • You work in order to reduce feelings of guilt, anxiety, helplessness or depression.
  • You have been told by others to cut down on work without listening to them.
  • You become stressed if you are prohibited from working.
  • You deprioritize hobbies, leisure activities, and/or exercise because of your work.
  • You work so much that it has negatively influenced your health.

Participants scoring 4 (often) or 5 (always) on four or more criteria identify a workaholic.

Researcher and clinical psychologist Specialist Cecilie Schou Andreassen, at the University of Bergen (UiB), and visiting scholar at the UCLA Semel Institute for Neuroscience and Human Behavior, said that "workaholics scored higher on all the psychiatric symptoms than non-workaholics."

  • 32.7 per cent met ADHD criteria (12.7 per cent among non-workaholics).
  • 25.6 per cent OCD criteria (8.7 per cent among non-workaholics).
  • 33.8 per cent met anxiety criteria (11.9 per cent among non-workaholics).
  • 8.9 per cent met depression criteria (2.6 per cent among non-workaholics).

People who work to the extreme may have deeper psychological or emotional issues. But whether the disorder leads to workaholism, or workaholism causes discorders it still unclear.

To be safe, make sure you relax this weekend!

To see the full study, visit here.

33 comments; last comment on 06/08/2016
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The Ziggurat Roofs of Bermuda

Posted May 27, 2016 8:00 AM by BestInShow

You're an island in the subtropical North Atlantic, with no freshwater lakes or streams. Nothing but salt water all around you. How do you provide fresh water for a population of 60,000 residents and more than 200,000 visitors a year? Your residents use technology that's nearly 400 years old. This technology not only catches and stores rainwater, it also helps keep buildings cool in hot weather and firmly on the ground during hurricanes. Despite changes in materials of construction, the Bermuda Roof - required by the island's building code -- graces the tops of houses all over Bermuda. The design makes so much sense it's used in other countries as well.

Bermuda Roof. Image source: Wikimedia Commons

Some history

The first English colonists arrived on Bermuda in 1609, rather by accident. The Sea Venture, a ship taking passengers to the Jamestown colony in Virginia, foundered on the surrounding coral reef during a hurricane. The passengers elected to remain on the island even after completing a replacement ship some months later. The lack of fresh water was readily apparent; although some water filters through the island's coral surface to underground lenses, the original settlers weren't prepared to locate and drill for it. So the new residents started harvesting rainwater.

The ingenious method Bermudians devised to collect rainwater is to create stepped roofs - hence, the ziggurat - that guide rainwater to a slanted gutter. The gutter connects via pipes to an underground cistern or holding tank, where water is stored until needed. Current building codes require Bermudians to make at least 80 percent of a roof's square footage a rainwater catchment area. With an average annual rainfall of 55 inches, that's a lot of water to catch and save.

The system

The rainwater-collection system incorporates more than just the gutter-to-cistern path. Several critical components lead to this system's success. These roofs, whether old or brand new, are nearly hurricane-proof; the Bermuda building code requires that roofs weigh 66 pounds per square foot (that's what the scuba boat pilot told Mr. Best in Show and me).

Roof composition: The original roofs were made of limestone "shingles," oblong slices of the island's native limestone mortared down over a hip-roof frame made of Bermuda cedar. The finished roof is then mortared over to fill in joints. Since the island can no longer supply limestone and cedar, contemporary roof slates are made of modern materials, such as expanded polystyrene (EPS), laid on a cement substrate.

Roof coating: Original roofs sported bright-white coatings of lime - essentially whitewash. This bright coating reflected the sun's glare, helping keep buildings cooler, and helped sanitize the rainwater. Today's roofers use white elastomeric paint. Although this material lasts longer than whitewash, homeowners still have to repaint every two or three years. This coating, like whitewash, helps prevent mildew and mold.

Gutters: Unlike conventional roof gutters, Bermuda roof gutters run slantwise across the slates, starting about two-thirds of the way down the roof, carrying rainwater through a pipe to the underground storage cistern. The gutters themselves are fashioned from cement.

Roof gutter on Bermuda Roof. Image credit: The A Position

Cistern: Rainwater passes through a filtration system as it funnels into below-ground cisterns. The cistern stores water, pumping it into a pressurized tank for distribution through the plumbing system.

Maintenance: Homeowners have to clean their roofs periodically to remove bird droppings and other foreign materials. As mentioned above, roof coatings last two or three years, necessitating re-coating at regular intervals. Public health experts recommend regular tank cleaning to ensure potable water.

Side benefits of the Bermuda Roof

A white-painted roof reflects sunlight back into the atmosphere, helping to keep the building it shelters cool. Something I didn't know is that, according to Lawrence Berkeley National Laboratory 1000 square feet of white roof has the equivalent effect of cutting 10 tons of carbon dioxide emissions. Multiply that by all of the white roofs in Bermuda, and the CO2 equivalent reduction is noticeable.

As mentioned above, the heavy roof prevents Bermudian homes from becoming airborne during hurricanes. The roof shingles, much less the entire roof, don't blow

off in high winds. Thanks to the mortar and roof sealant, these roofs are watertight, as well.

Aesthetically, the consistent use of this style of roof, coupled with the pastel paint used on Bermuda buildings large and small, contribute greatly to the charm of this British Overseas Territory. Bermudian indigenous architecture is considered by some to be the island's greatest artistic heritage.

The downside

Recent studies indicate that general cistern water quality isn't necessarily as good as one expects from a traditional municipal water supply or private well. Two years ago, a Canadian public health specialist from UniversiteĀ“ Laval in Quebec alarmed Bermudians when he claimed that cistern water contains too much fecal matter to be safe to drink. Dr. Eric Dewailly based his statement on research completed in 2013. He proposed that bird droppings are the most likely source of fecal-matter bacteria, highlighting the need to clean roofs regularly. Dr. Dewailly encouraged residents to incorporate an ultraviolet treatment system to kill bacteria.

A study of the mineral composition of cistern water produced more equivocal results. Sediments that accumulate in cisterns can contain elevated levels of nasty stuff like arsenic, but the levels vary from tank to tank. The authors called for more research to clarify the picture.


Image credit:

Bermuda roof on building on Corfu. Corfu Blues Blog.

7 comments; last comment on 06/10/2016
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Grow Plants in Rocks! Innovative Horticultural Substrates

Posted May 20, 2016 8:00 AM by BestInShow

When I was researching my previous post, on living walls, I discovered that an inorganic substance, stone wool, is used as a growing substrate for some wall systems. Stone wool? I'd never heard of such a thing. The more I looked into this topic, the more interesting substrates I found. These all represent advances in the horticultural use of existing materials, some of them organic like coconut coir, some, like rock wool, inorganic. Improvements in substrate materials have no doubt contributed to the increase in living walls; the same improvements are a boon to horticulture in general.

What's a substrate?

Simply put, a horticultural substrate is a substance in which a plant's roots grow. Garden soil is a substrate. Vermiculite is a substrate. Plants do not need potting soil, or even organic matter, for growth. They do need something that holds roots firmly enough to enable the plant to grow up and that allows water and nutrients to reach the roots.

Why look for different substrates?

In the 1960s, a couple of factors impelled the commercial horticulture industry to seek out new types of plant growth substrates. The growing environmental movement awakened concerns about increasingly intensive use of farmland, which exhausts the land. These concerns led, among other actions, to the banning of methyl bromide, a soil disinfectant commonly used to prepare soil for planting. Finding new methods for crop culture would take pressure off of existing resources.

Stone wool

I'd never heard of stone wool, and I was baffled that something made out of basalt would be an acceptable plant substrate. Although mineral wool insulation has been around for a long time, a mistake - a bad batch of insulation - led to its use as a plant growth substrate. A Danish insulation manufacturer, the ROCKWOOL group, tossed the defective stone wool out on factory property. Lo and behold, sometime later staff noted that small plants were growing in the insulation batts.

The company worked with university researchers to perfect this stone wool for

use in horticulture. A subsidiary of ROCKWOOL, GRODAN, manufactures the horticultural version of RockwoolĀ©. Plant propagators use cubes of the material for starting seeds or rooting cuttings. It offers several advantages for green walls and more general plant-growing applications:

  • The medium is consistent in makeup from batch to batch, and it's easily sterilized.
  • Stone wool is hydrophilic, which enables efficient circulation and recirculation water and nutrients, but it does not rot like organic substances.
  • Plant roots have plenty of room to grow between fibers.
  • Since stone wool substrate does not lock up or release any substances, growers can provide precise amounts of water and nutrients.
  • Stone wool is lightweight.

Coconut coir

Coconut or coco coir is the fibrous material found between the hard interior shell and the outer coat of a coconut. We're familiar with many of the products made of coir, whose production goes back as far as the 11th century AD: doormats, ropes, sacking, twine, among

others. During the 1990s, coir's advantages as a horticultural substrate attracted commercial growers, and it's popular today, particularly for hydroponics and mushroom cultivation. At least one company sandwiches coir mats into panels for vertical gardening. In addition to sheets and loose chopped fibers, horticultural-use coir is formed into bricks and cubes.

Coir offers several advantages as a growth substrate, not least of which is the attractive natural tan-to-brown color of coir sheets and bricks. Other advantages include that

  • Coir can hold up to five times its weight in water and release it slowly, yet it drains well and prevents water pooling and rot.
  • Coir is very slightly acidic, with good pH for plant growth.
  • Roots move easily into the pores between coir fibers.
  • Depending on its origin, coir can contain usable amounts of plant nutrients, such as phosphorus.
  • Coir has some anti-fungal properties and inhibits some other pathogens.
  • This medium is long-lasting and can be reused for three to four years.
  • Coir is a 100 percent renewable resource.

A problem recently noted with some coir products is the potential for inadvertent importation of exotic weed species. Ironically, gardeners can use coir mats to inhibit weed growth.

Felt systems

Patrick Blanc, the genius behind contemporary vertical gardens, started out using synthetic felt, irrigating plants with nutrient-laden water. Fast-forward to the 21st century for the introduction of an improved type of felt for vertical gardening. This new felt is made from 100 percent recycled plastic bottles, so it's environmentally friendly and durable.

At least two companies market pockets made from recycled-plastic felt, with two slightly-different pocket designs and configurations. Both designs make use of the felt's capacity to wick water throughout the pocket. Both designs also incorporate at least a minimum amount of another growth substrate, typically a soil-less mixture. Plant roots can penetrate the felt.

Florafelt Vertical Garden Planter Woollypocket Planter

These pockets make small-scale vertical gardening easy, indoors or outside. They can be hung on drywall without causing water damage, and gardeners can swap out and rearrange plants easily. Home gardeners that lack access to a plot of ground can use these pouches to grow vegetables and herbs - perhaps not squashes, but definitely lettuce and other smallish plants -- indoors or on a deck or patio.


Photo credits: Rockwool/Wikimedia Commons;; Florafelt; Woollypocket

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