System designed for household and neighborhood power generation
RICHLAND, Wash. – Individual homes and entire neighborhoods could be powered with a new, small-scale solid oxide fuel cell system that achieves up to 57 percent efficiency, significantly higher than the 30 to 50 percent efficiencies previously reported for other solid oxide fuel cell systems of its size, according to a study published in this month's issue of Journal of Power Sources.
The smaller system, developed at the Department of Energy's Pacific Northwest National Laboratory, uses methane, the primary component of natural gas, as its fuel. The entire system was streamlined to make it more efficient and scalable by using PNNL-developed microchannel technology in combination with processes called external steam reforming and fuel recycling. PNNL's system includes fuel cell stacks developed earlier with the support of DOE's Solid State Energy Conversion Alliance.
"Solid oxide fuels cells are a promising technology for providing clean, efficient energy. But, until now, most people have focused on larger systems that produce 1 megawatt of power or more and can replace traditional power plants," said Vincent Sprenkle, a co-author on the paper and chief engineer of PNNL's solid oxide fuel cell development program. "However, this research shows that smaller solid oxide fuel cells that generate between 1 and 100 kilowatts of power are a viable option for highly efficient, localized power generation."
Sprenkle and his co-authors had community-sized power generation in mind when they started working on their solid oxide fuel cell, also known as a SOFC. The pilot system they built generates about 2 kW of electricity, or how much power a typical American home consumes. The PNNL team designed its system so it can be scaled up to produce between 100 and 250 kW, which could provide power for about 50 to 100 American homes.
Goal: Small and efficient
Knowing the advantages of smaller SOFC systems (see the "What is an SOFC?" sidebar below for more information), the PNNL team wanted to design a small system that could be both more than 50 percent efficient and easily scaled up for distributed generation. To do this, the team first used a process called external steam reforming. In general, steam reforming mixes steam with the fuel, leading the two to react and create intermediate products. The intermediates, carbon monoxide and hydrogen, then react with oxygen at the fuel cell's anode. Just as described in the below sidebar, this reaction generates electricity, as well as the byproducts steam and carbon dioxide.
Steam reforming has been used with fuel cells before, but the approach requires heat that, when directly exposed to the fuel cell, causes uneven temperatures on the ceramic layers that can potentially weaken and break the fuel cell. So the PNNL team opted for external steam reforming, which completes the initial reactions between steam and the fuel outside of the fuel cell.
The external steam reforming process requires a device called a heat exchanger, where a wall made of a conductive material like metal separates two gases. On one side of the wall is the hot exhaust that is expelled as a byproduct of the reaction inside the fuel cell. On the other side is a cooler gas that is heading toward the fuel cell. Heat moves from the hot gas, through the wall and into the cool incoming gas, warming it to the temperatures needed for the reaction to take place inside the fuel cell.
Efficiency with micro technology
The key to the efficiency of this small SOFC system is the use of a PNNL-developed microchannel technology in the system's multiple heat exchangers. Instead of having just one wall that separates the two gases, PNNL's microchannel heat exchangers have multiple walls created by a series of tiny looping channels that are narrower than a paper clip. This increases the surface area, allowing more heat to be transferred and making the system more efficient. PNNL's microchannel heat exchanger was designed so that very little additional pressure is needed to move the gas through the turns and curves of the looping channels.
The second unique aspect of the system is that it recycles. Specifically, the system uses the exhaust, made up of steam and heat byproducts, coming from the anode to maintain the steam reforming process. This recycling means the system doesn't need an electric device that heats water to create steam. Reusing the steam, which is mixed with fuel, also means the system is able to use up some of the leftover fuel it wasn't able to consume when the fuel first moved through the fuel cell.
The combination of external steam reforming and steam recycling with the PNNL-developed microchannel heat exchangers made the team's small SOFC system extremely efficient. Together, these characteristics help the system use as little energy as possible and allows more net electricity to be produced in the end. Lab tests showed the system's net efficiency ranged from 48.2 percent at 2.2 kW to a high of 56.6 percent at 1.7 kW. The team calculates they could raise the system's efficiency to 60 percent with a few more adjustments.
The PNNL team would like to see their research translated into an SOFC power system that's used by individual homeowners or utilities.
"There still are significant efforts required to reduce the overall cost to a point where it is economical for distributed generation applications," Sprenkle explained. "However, this demonstration does provide an excellent blueprint on how to build a system that could increase electricity generation while reducing carbon emissions."


Wheezing is a high-pitched whistling sound during breathing. It occurs when air moves through narrowed breathing tubes.
Wheezing is a sign that a person may be having breathing problems. The sound of wheezing is most obvious when breathing out (exhaling), but may be heard when taking a breath (inhaling).
Wheezing most often comes from the small breathing tubes (bronchial tubes) deep in the chest, but it may be due to a blockage in larger airways or in persons with certain vocal cord problems.
Click to download
Always take all of your medications as directed.
Sitting in an area where there is moist, heated air may help relieve some symptoms. This can be done by running a hot shower or using a vaporizer.
Call your health care provider if
Call your health care provider if:
If wheezing is severe or occurs with severe shortness of breath, you may have to go directly to the nearest emergency department.
What to expect at your health care provider's office
The doctor or nurse will perform a physical examination and ask questions about your medical history and symptoms, including:
- When did the wheezing begin?
- How long does it last?
- When and how often does it occur?
- Is it worse at night or in the early morning?
- What does the wheezing sound like?
- Does it make breathing difficult?
- What seems to cause it?
- Eating certain foods?
- Taking certain medications?
- Do any of the following things make it worse?
- Being around pollens, insects, dust, chemicals (perfumes, cosmetics)
- Being in cold air
- Sickness (such as a cold or the flu)
- Does it go away without treatment?
- What helps relieve it?
- Medications such as bronchodilators?
- Do you have any other symptoms, such as:
- Did you have an episode of choking
- Did you have an insect bite?
- Do you have a history of asthma
- What medications do you take?
- Have you been around tobacco smoke?
- Have you recently been sick?
The physical examination may include listening to the lung sounds (auscultation
). If your child is the one with symptoms, the doctor will make sure he or she did not swallow a foreign object.
Tests that may be done include:
- Blood work, possibly including arterial blood gases
- Chest x-ray
- Lung function tests
A hospital stay may be needed if:
Breathing is particularly difficult
Medicines need to be given through a vein (IV)
Supplemental oxygen is required
The person needs to be closely watched by medical personnel
Schatz M. Asthma in adolescents and adults. In: Bope ET, Rakel RE, Kellerman R, eds. Conn’s Current Therapy 2012. 2nd ed. Philadelphia, Pa: Saunders Elsevier; 2012:section 6.
Szefler SJ. Advances in pediatric asthma in 2009: gaining control of childhood asthma. J Allergy Clin Immunol. 2010 Jan;125(1):69-78.
Neil K. Kaneshiro, MD, MHA, Clinical Assistant Professor of Pediatrics, University of Washington School of Medicine. Also reviewed by David Zieve, MD, MHA, Medical Director, A.D.A.M. Health Solutions, Ebix, Inc.


It may be the site of the town of Hilfa, which is mentioned in the Talmud. The foundations of an ancient synagogue were discovered near there in 1929 by explorations done on behalf of the Hebrew University. The synagogue, measuring 46 x 92 feet, included a courtyard, hall, two side aisles and a women's gallery. It faced south toward Jerusalem. A small cavity in the floor probably served as a genizah; above it was an Ark for scrolls of the Law. The whole floor of the building is paved with mosaics.
Two inscriptions were found at the entrance to the hall. One, in Aramaic, states that the mosaics were made during the reign of Emperor Justin (518--527). The other, in Greek, gives the names of those who made the mosaics, Marianos and his son Hanina. There are three mosaic panels in the center of the hall. The first shows the Akedah, the binding of Isaac on the altar. The second mosaic represents the signs of the Zodiac. The third depicts a synagogue ark with a gabled roof and an "eternal light" suspended from its top. On either side is a lion with a seven-branched menorah. Above the menorah and between the lions are pictured ritual items such as lulavim (palm branches), etrogim (citrons), and incense holders. Curtains adorned it on either side. The designs are simple and strong. In these mosaics, the artists took great care to make each scene expressive. The mosaics of Bet Alfa are striking in their coloring and style, and are among the finest examples of Jewish art in the Byzantine period.
Kibbutz Bet Alfa was founded at in 1922.
A scene at one of the children's houses
Making up the daily work schedule (August 1946)
A Man with his cow (August 1930)


Literary Research Paper
Simple Ways To Write A Literary Research Paper
Unlike most other research papers, a literary research paper generally requires an argumentative style of writing rather than a descriptive style. Loads of support content would be available to support an opinion, but knowing how to present it is a totally different ball game.
The topics in these research papers may vary from character analysis of a fictitious character to analyzing the change in writing styles of different authors. Different alternative endings may have to be suggested for a plot. For instance, the assignment could be to write a critical commentary on a Shakespearian tragedy or Joyce’s writing. Attempting such varied topics is not easy. It is absolutely essential that research is conducted the right way to come up with a decent paper.
Guidelines To Adapt While Writing A Literary Research Paper
- Read the whole works several times. Literature is interesting, and reading it often makes you an expert on the piece. Ideas develop in your mind, which then become part of the review process.
- Have a fair idea of your own opinion on the topic. Personal opinions carry great weight, because readers are more interested in what is written about the storyline .They may or may not actually know the story in detail.
- Learn to come up with your own original content after you have read the piece of literature. Attempt writing each paragraph and try to rewrite it with your own ideas in place. This is a practical way to improve writing skills.
- Develop the right research skills. For instance, to write a review of William Shakespeare’s style of writing, check other works by the same author. It would offer you further insight.
ResearchPaperWriter.net specializes in providing you with your own blueprint for the essay. Experienced writers are at hand to guide you along the way. The dedicated writer would most certainly assist in putting your thoughts together in your literary research paper. A draft of the essay is reviewed at every step, and we can even assist you in choosing the style and format to best suit the nature of your essay. When the right metaphor or quotation eludes you, rely on us to supply you with the appropriate alternative.
Be it the pre-classical poems of Byron and Shelley or the cold, morbid nature of a Dostovievskian character, we have expert writers on our panel to ease your workload. To help you make a decision, we have provided research paper samples to suit various levels of writing.
ResearchPaperWriter.net has achieved excellence in the field of academic writing, and caters to a wide range of students and researchers. We leave no stone unturned in ensuring that our clientele get the best custom writing services. Our authors use the latest anti-plagiarism software to ensure that all research papers are original.
Correspondence with our clients is always strictly confidential. For a very nominal amount, you can choose to avail of our services. We guarantee that your order for a literary research paper will be well received and appreciated.


Type of Culminating Activity
Graduate Student Project
As world-wide energy consumption continues to increase, so does the demand for the use of alternative energy sources, such as Nuclear Energy. Nuclear Power Plants currently supply over 370 gigawatts of electricity, and more than 60 new nuclear reactors have been commissioned by 15 different countries. The primary concern for Nuclear Power Plant operation and lisencing has been safety. The safety of the operation of Nuclear Power Plants is no simple matter- it involves the training of operators, design of the reactor, as well as equipment and design upgrades throughout the lifetime of the reactor, etc. To safely design, operate, and understand nuclear power plants, industry and government alike have relied upon the use of best-estimate simulation codes, which allow for an accurate model of any given plant to be created with welldefined margins of safety. The most widely used of these best-estimate simulation codes in the Nuclear Power industry is RELAP5-3D. Our project focused on improving the modeling capabilities of RELAP5-3D by developing uncertainty estimates for its calculations. This work involved analyzing high, medium, and low ranked phenomena from an INL PIRT on a small break Loss-Of-Coolant Accident as well as an analysis of a large break Loss-Of-Coolant Accident. Statistical analyses were performed using correlation coefficients. To perform the studies, computer programs were written that modify a template RELAP5-3D input deck to produce one deck for each combination of key input parameters. Python scripting enabled the running of the generated input files with RELAP5-3D on INL’s massively parallel cluster system. Data from the studies was collected and analyzed with SAS. Summaries of the results of our studies are presented.
Gertman, Alexandra E. and Mesina, George L., "Uncertainty Analysis of RELAP5-3D©" (2012). Mathematics Graduate Projects and Theses. Paper 1.


Charles Robert Darwin (18091882). Origin of Species. The Harvard Classics. 190914.
XI. On the Geological Succession of Organic Beings
On the Forms of Life Changing Almost Simultaneously throughout the World
SCARCELY any palæontological discovery is more striking than the fact that the forms of life change almost simultaneously throughout the world. Thus our European Chalk formation can be recognised in many distant regions, under the most different climates, where not a fragment of the mineral chalk itself can be found; namely in North America, in equatorial South America, in Tierra del Fuego, at the Cape of Good Hope, and in the peninsula of India. For at these distant points, the organic remains in certain beds present an unmistakable resemblance to those of the Chalk. It is not that the same species are met with; for in some cases not one species is identically the same, but they belong to the same families, genera, and sections of genera, and sometimes are similarly characterised in such trifling points as mere superficial sculpture. Moreover, other forms, which are not found in the Chalk of Europe, but which occur in the formations either above or below, occur in the same order at these distant points of the world. In the several successive palæozoic formations of Russia, Western Europe, and North America, a similar parallelism in the forms of life has been observed by several authors; so it is, according to Lyell, with the European and North American tertiary deposits. Even if the few fossil species which are common to the Old and New Worlds were kept wholly out of view, the general parallelism in the successive forms of life, in the palæozoic and tertiary stages, would still be manifest, and the several formations could be easily correlated.
These observations, however, relate to the marine inhabitants of the world: we have not sufficient data to judge whether the productions of the land and of fresh water at distant points change in the same parallel manner. We may doubt whether they have thus changed: if the Megatherium, Mylodon, Macrauchenia, and Toxodon had been brought to Europe from La Plata, without any information in regard to their geological position, no one would have suspected that they had co-existed with seashells all still living; but as these anomalous monsters co-existed with the mastodon and horse, it might at least have been inferred that they had lived during one of the later tertiary stages.
When the marine forms of life are spoken of as having changed simultaneously throughout the world, it must not be supposed that this expression relates to the same year, or to the same century, or even that it has a very strict geological sense; for if all the marine animals now living in Europe, and all those that lived in Europe during the pleistocene period (a very remote period as measured by years, including the whole glacial epoch) were compared with those now existing in South America or in Australia, the most skilful naturalist would hardly be able to say whether the present or the pleistocene inhabitants of Europe resembled most closely those of the southern hemisphere. So, again, several highly competent observers maintain that the existing productions of the United States are more closely related to those which lived in Europe during certain late tertiary stages, than to the present inhabitants of Europe; and if this be so, it is evident that fossiliferous beds now deposited on the shores of North America would hereafter be liable to be classed with somewhat older European beds. Nevertheless, looking to a remotely future epoch, there can be little doubt that all the more modern marine formations, namely, the upper pliocene, the pleistocene and strictly modern beds of Europe, North and South America, and Australia, from containing fossil remains in some degree allied, and from not including those forms which are found only in the older underlying deposits, would be correctly ranked as simultaneous in a geological sense.
The fact of the forms of life changing simultaneously, in the above large sense, at distant parts of the world, has greatly struck these admirable observers, MM. de Verneuil and dArchiac. After referring to the parallelism of the palæozoic forms of life in various parts of Europe, they add, If, struck by this strange sequence, we turn our attention to North America, and there discover a series of analogous phenomena, it will appear certain that all these modifications of species, their extinction, and the introduction of new ones, cannot be owing to mere changes in marine currents or other causes more or less local and temporary, but depend on general laws which govern the whole animal kingdom. M. Barrande has made forcible remarks to precisely the same effect. It is, indeed, quite futile to look to changes of currents, climate, or other physical conditions, as the cause of these great mutations in the forms of life throughout the world, under the most different climates. We must, as Barrande has remarked, look to some special law. We shall see this more clearly when we treat of the present distribution of organic beings, and find how slight is the relation between the physical conditions of various countries and the nature of their inhabitants.
This great fact of the parallel succession of the forms of life throughout the world, is explicable on the theory of natural selection. New species are formed by having some advantage over older forms; and the forms, which are already dominant, or have some advantage over the other forms in their own country, give birth to the greatest number of new varieties or incipient species. We have distinct evidence on this head, in the plants which are dominant, that is, which are commonest and most widely diffused, producing the greatest number of new varieties. It is also natural that the dominant, varying, and far-spreading species, which have already invaded to a certain extent the territories of other species, should be those which would have the best chance of spreading still further, and of giving rise in new countries to other new varieties and species. The process of diffusion would often be very slow, depending on climatal and geographical changes, on strange accidents, and on the gradual acclimatisation of new species to the various climates through which they might have to pass, but in the course of time the dominant forms would generally succeed in spreading and would ultimately prevail. The diffusion would, it is probable, be slower with the terrestrial inhabitants of distinct continents than with the marine inhabitants of the continuous sea. We might therefore expect to find, as we do find, a less strict degree of parallelism in the succession of the productions of the land than with those of the sea.
Thus, as it seems to me, the parallel, and, taken in a large sense, simultaneous, succession of the same forms of life throughout the world, accords well with the principle of new species having been formed by dominant species spreading widely and varying; the new species thus produced being themselves dominant, owing to their having had some advantage over their already dominant parents, as well as over other species, and again spreading, varying, and producing new forms. The old forms which are beaten and which yield their places to the new and victorious forms, will generally be allied in groups, from inheriting some inferiority in common; and therefore, as new and improved groups spread throughout the world, old groups disappear from the world; and the succession of forms everywhere tends to correspond both in their first appearance and final disappearance.
There is one other remark connected with this subject worth making. I have given my reasons for believing that most of our great formations, rich in fossils, were deposited during periods of subsidence; and that blank intervals of vast duration, as far as fossils are concerned, occurred during the periods when the bed of the sea was either stationary or rising, and likewise when sediment was not thrown down quickly enough to embed and preserve organic remains. During these long and blank intervals I suppose that the inhabitants of each region underwent a considerable amount of modification and extinction, and that there was much migration from other parts of the world. As we have reason to believe that large areas are affected by the same movement, it is probable that strictly contemporaneous formations have often been accumulated over very wide spaces in the same quarter of the world; but we are very far from having any right to conclude that this has invariably been the case, and that large areas have invariably been affected by the same movements. When two formations have been deposited in two regions during nearly, but not exactly, the same period, we should find in both, from the causes explained in the foregoing paragraphs, the same general succession in the forms of life; but the species would not exactly correspond; for there will have been a little more time in the one region than in the other for modification, extinction, and immigration.
I suspect that cases of this nature occur in Europe. Mr. Prestwich, in his admirable Memoirs on the eocene deposits of England and France, is able to draw a close general parallelism between the successive stages in the two countries; but when he compares certain stages in England with those in France, although he finds in both a curious accordance in the numbers of the species belonging to the same genera, yet the species themselves differ in a very, difficult to account for, considering the proximity of the two areas,unless, indeed, it be assumed that an isthmus separated two seas inhabited by distinct, but contemporaneous, faunas. Lyell has made similar observations on some of the later tertiary formations. Barrande, also, shows that there is a striking general parallelism in the successive Silurian deposits of Bohemia and Scandinavia; nevertheless he finds a surprising amount of difference in the species. If the several formations in these regions have not been deposited during the same exact periods,a formation in one region often corresponding with a blank interval in the other,and if in both regions the species have gone on slowly changing during the accumulation of the several formations and during the long intervals of time between them; in this case the several formations in the two regions could be arranged in the same order, in accordance with the general succession of the forms of life, and the order would falsely appear to be strictly parallel; nevertheless the species would not be all the same in the apparently corresponding stages in the two regions.


stockArticle Free Pass
stock, in finance, the subscribed capital of a corporation or limited-liability company, usually divided into shares and represented by transferable certificates. The certificates may detail the contractual relationship between the company and its stockholders, or shareholders, and set forth the division of the risk, income, and control of the business.
Common stock, or ordinary shares.
Many companies have only one class of stock, often called common stock, or ordinary shares. This class of stock carries residual ownership of the company, entitling the holder to unlimited interest in the earnings and assets of the company after limited claims are paid. Common stockholders have the right to control the company through their voting rights, unless such rights are specifically withheld, as in special classes of “nonvoting” shares. The common stockholders’ legal rights may also include preemptive rights to maintain their proportion of equity when new stock is issued. Dividends paid on common stock are usually unstable because they tend to vary with earnings; they are also usually less than earnings, the difference being used by management to expand the firm and allow the stockholders’ equity to grow. The market price of common stock is often subject to wide fluctuations, because it depends largely upon investors’ expectations of future earnings.
Preferred stock, or preference shares.
To appeal to investors who wish to be sure of receiving dividends regularly, many companies issue what is called preferred stock, or preference shares. This class of stock has a prior claim to dividends paid by the company and, usually, to the assets of the company in the event of its dissolution. Dividends are usually set at a fixed annual rate that must be paid before dividends are distributed to the common stockholders. Preferred stock may be participating, meaning that its holders share with common stockholders in any company earnings over and above the stated dividends on the preferred stock. Preferred stock may be cumulative or noncumulative: if cumulative, dividends not paid in one year must be paid in addition to dividends earned in the following year, before any dividend payments are made on the common stock.
What made you want to look up "stock"? Please share what surprised you most...


Originally printed in 1997, this revised "Orion DeepMap 600" is among those indispensable publications that Company Seven recommends to anyone who interested in learning their way around the night sky. The editor Steve Peters conceived of this as a very helpful device for anyone interested in astronomy and who may little or no observational experience. This has become the most popular chart of the night sky among our customers who are new to the hobby and who buy a telescope or binocular and now seek out what to see and when. This is often bought as a economical but valued and durable gift.
Fully color illustrated, it is the first-ever star chart that folds up like a road map! DeepMap 600 shows the positions of more than six hundred of the finest celestial objects visible from the Northern Hemisphere. Each of these objects are plotted on a giant 33 x 21 inch full-color star chart by world-renowned celestial cartographer Wil Tirion. But what really makes this star chart invaluable is its convenience; it folds "accordion style" into a thin, pocket-size 4-¾ x 10-½ inches format - just like a road map!
Even with no knowledge of the night sky one should be able to go out and find the patterns that make up the larger Constellations, and then match them to the DeepMap 600 chart to obtain their orientation to the night sky. But note that since this does mention some astronomical/navigational terms (zenith, meridian, latitude, magnitude, etc.) then a little homework about these terms in advance of going out at night with this chart will help the least understanding buyer to mover forward quickly.
Above: sample of the Star Chart showing some of the symbols and nomenclature about to scale, and all readable by red light (189,505 bytes).
On the side opposite the chart is a map of the northern circumpolar region, as well as a listing of essential data for each of the objects plotted on the DeepMap 600 chart. The information including coordinates (very helpful for those who have telescopes with Setting Circles), apparent magnitude (to help one know how bright the object is), angular size ('how big is big'), and even a brief description of how it will appear to the eye when looking through binocular or a telescope. Instructions offers tips on using the "Orion DeepMap 600", with general observing hints, and more.
The contrast and clarity of your computer screen are not likely to match the original so you may click on image to see enlarged view (487,844 bytes).
No longer must you fumble with bulky books, star atlases, and observing references to find interesting objects to view. The quick-reference DeepMap 600 is all you need to get started.


WebMD Medical News
Brenda Goodman, MA
Laura J. Martin, MD
July 14, 2011 -- People who say they vigilantly apply sunscreen are more likely to experience painful, damaging sunburns, a new study shows.
The study, the first to look at how people in the U.S. shield themselves from the sun and how well those different strategies work, analyzed information on more than 3,000 white adults that was collected through the National Health and Nutrition Examination Survey.
Sunscreen was the most commonly used kind of protection, grabbing the top spot with 30% of people saying they regularly apply it when they’re outside for longer than an hour.
The next most common skin-saving strategies were seeking shade (25% said they frequently stayed under cover when the sun was blazing), wearing a hat (16%), and donning long sleeves (6%).
People who said they frequently used sunscreen, however, had 23% greater risk of multiple sunburns in the past year compared to people who said they seldom used the stuff.
Those who frequently sought shade and pulled on long sleeves, however, had about a 30% lower sunburn risk compared to people who rarely used those measures.
Those risks remained even after researchers corrected for factors known to influence burn risk, including the skin’s sensitivity to the sun, alcohol use, season, physical activity, age, gender, education, and income.
“I really like this study,” says Ronald P. Rapini, MD, professor and chairman of the department of dermatology at the University of Texas M.D. Anderson Cancer Center in Houston. “I’ve always felt the same way, and I tell my patients the same thing.”
“Just last week, one of my melanoma patients came in with a sunburn all over their back, and I said, ‘What happened?’ and they said, ‘Well, I had sunscreen.’ But they missed an area on their back, which is what always happens. They think that they can stay out in the sun because they’re using sunscreen, and the truth is it doesn’t really cover stuff that well,” says Rapini, who was not involved in the research.
“Myself, personally, I’m a dermatologist, and I don’t even wear sunscreen all that much. I stay in the shade,” he says. “I try to stay out of the sun.”
The study is published in the journal Cancer Causes & Control.
“I was quite surprised to find the associations that we’ve found with the different types of sun protection,” says study researcher Eleni Linos, MD, DrPH, MPH, a dermatologist at Stanford University.
“What we saw was that wearing long-sleeved clothing, wearing a hat, and staying in the shade were associated with fewer sunburns,” she says. “However, wearing sunscreen was actually associated with more sunburns.”
Linos is quick to point out that her results don’t mean that sunscreen doesn’t work or shouldn’t be used.
The study was designed to look at patterns, not to prove cause and effect.
It’s possible that people with the fairest, most easily burned skin are also simply the group most likely to use sunscreen.
But if that were the case, Linos says, she would have expected to see the same phenomenon across all the different groups. That is, frequent shade seekers and long-sleeve wearers would also report having more burns compared to those who rarely reported those tactics.
The more likely explanation, she thinks, is user error -- people simply aren’t applying as much sunscreen as often as they should.
Numerous studies have shown that most people, even after they’re carefully schooled in proper sunscreen application, still don’t get enough on.
One of the latest, from researchers in Brazil, asked study participants to cover both forearms with sunscreen, and 30 minutes later, to reapply the sunscreen to just one arm.
Researchers used tape strips to measure how thickly the lotion went on.
Sunscreen is tested to work at its SPF when it’s applied to a depth of at least 2 milligrams per square centimeter on the skin.
After the first application, study participants got only a quarter of that amount on. For the arm that got the second application, the depth of the sunscreen eventually reached half of what it should have been, suggesting that even people who remember to reapply aren’t being fully protected.
Another problem is that many people rely on sunscreen as their sole form of protection, when really, shade and protective clothing need to be part of a multi-pronged approach to avoiding sunburns, which increase the risk of skin cancer.
“There’s still a lot of work that we as physicians, especially dermatologists, need to do to educate individuals about proper photoprotection,” says Henry W. Lim, MD, chair of the department of dermatology at Henry Ford Health System in Detroit.
He says this study is consistent with previous research.
“It’s known that people use sunscreen, but they don’t use it at the appropriate amount and because of that, they have a false sense of a security,” says Lim, who was not involved in the research.
That false sense of security can lead people to stay in the sun longer than they safely should, leading to an increased risk of sunburns and greater UV exposure, which can cause skin cancer.
Sunscreen use has been shown to reduce some kinds of skin cancers, however, and earlier this year, a prospective study, the first of its kind, found that regular sunscreen use in a group of 1,621 Australian adults cut their risk of melanoma by 50%.
Importantly, however, the study participants in that trial carefully and repeatedly applied sunscreen while also seeking shade and wearing protective clothing.
“The best data that’s out there shows the combination of seeking shade, wearing protective clothing and wearing sunscreen, those three things together clearly lower your risk,” says Darrell S. Rigel, MD, a clinical professor of dermatology at New York University.
Rigel says there is an important caveat about this study which should reassure people about their sunscreen.
The latest data used in the study is now about five years old, and he says sunscreens have improved in a couple of key ways since then.
“How long it lasts, 'substantivity' it’s called, has markedly improved, really with new formulations,” he says, and many of the newer formulations offer better broad-spectrum protections against both UVB, the burning rays, and UVA, the cancer-causing rays.
New FDA rules for sunscreens, which will go into effect next year, should make it easier to pick a good product.
That’s important, Rigel points out, because it’s not always possible to stay in the shade or wear longs sleeves.
In those cases, it’s more important than ever to put sunscreen on correctly.
Experts say the rule of thumb is a golf ball-sized blob for every exposed body part, applied at least 30 minutes before going outside, since sunscreen takes that long to absorb into the skin.
That much sunscreen should be reapplied every two hours, and even more frequently, every 60 to 90 minutes, when swimming, sweating, or using a spray product, since those don’t last as long.
SOURCES:Linos, E. Cancer Causes & Control, June 2011.De Villa, D. Photochemistry and Photobiology, March-April 2011.Kester, B. Scandinavian Journal of Public Health, July 2010.Burnett, M. Photodermatology, Photoimmunology and Photomedicine, April 2011.Robinson J. Journal of the American Medical Association, June 28, 2011.Autier, P. Journal of Clinical Oncology, April 4, 2011.Ronald P. Rapini, MD, professor and chairman, department of dermatology, University of Texas M.D. Anderson Cancer Center, Houston.Eleni Linos, MD, DrPH, MPH, Stanford University.Henry W. Lim, MD, chair, department of dermatology, Henry Ford Health System, Detroit.Darrell S. Rigel, MD, clinical professor of dermatology, New York University.
Here are the most recent story comments.View All
The views expressed here do not necessarily represent those of KOKI FOX23 - Tulsa
The Health News section does not provide medical advice, diagnosis or treatment. See additional information.


You are here
Edward Elgar (1857-1934) was 50 years old before he began what was to become his first symphony. It was not, strictly speaking, his first attempt at a symphony: he had actually composed a symphony modeled on Mozart as an exercise 30 years earlier (only one movement survives), and in 1898 took a stab at a programmatic symphony based on the life of the English military-imperial hero General Gordon, which, fortunately, did not get far.
Any composer approaching the symphony after Beethoven might well have had some trepidation about it. Brahms’ difficulties with his first symphony were legend. By the early 20th century, there was the additional problem of whether the symphony’s day had passed. Though some composers of Elgar’s generation were moving away from the symphony, Elgar remained convinced that it was still viable. In a 1905 lecture at Birmingham University, he said
“It seems to me that because the greatest genius of our days, Richard Strauss, recognizes the symphonic-poem as a fit vehicle for his splendid achievements, some writers are inclined to be positive that the symphony is dead… but when the looked-for genius comes, it may be absolutely revived.”
A few years later, Elgar took it upon himself to be the “looked-for genius,” and the result was a staggering immediate success: the Symphony was performed about 100 times worldwide within a year after its premiere in December 1908. It has not done so well since, and is now only an occasional visitor to the standard repertory.
The Symphony might be regarded as a battle, a study of opposites in conflict: the stately versus the agitated, the singable diatonic melody against the sinewy chromatic theme, the foreboding against the triumphant. At the very outset, Elgar pens one of his most stately melodies (he already had four of the five “Pomp and Circumstance” marches behind him). Elgar uses the unusual key of A-flat major for this introduction and “motto” theme, but does not stay there long. The tumultuous Allegro begins in D minor, a key as far as possible from A-flat (Elgar wrote to his friend August Jaeger that he had “thrown over all key relationships as formerly practiced” but that he “was not silly enough to think (or wish) that I have invented anything” in the process), with the motto inserting itself, and its mood, into the storm, and eventually establishing calm at the end. Throughout the symphony, Elgar uses a peculiar device to insinuate motifs such as the motto in an almost subliminal way: he writes them as “solos” for the players on the last stand of a string section. He commented:
“I have employed the last desks of the strings to get a soft diffused sound: the listener need not be bothered to know where it comes from — the effect is of course different from that obtained from the first desk soli.”
The second movement is another kind of battle. A turbulent main section, (in another distant key, F-sharp minor) features a driving perpetual motion figure and an ominous quick march. It modulates to B-flat major, where gossamer strings, flutes, and harp play an idyllic interlude that Elgar said should be played “like something we hear down by the river.”
The perpetual motion figure reasserts itself, but gradually slows until, improbably, it becomes, note for note, the principal theme of the Adagio third movement. Both Hans Richter, who conducted the premiere, and August Jaeger, a longtime champion of Elgar’s music, compared this movement to the adagios of Beethoven, though to modern audiences it will more likely recall Mahler in its breadth, heart-on-sleeve passion, and richness (a richness which is due considerably to Elgar’s subdividing the strings into nine parts instead of the usual five).
The finale begins with another slow introduction, in D minor, in which a foreboding opening gives way to a minor-key march figure in the low strings and bassoons, and then to the motto theme. Elgar gives the march figure a series of startling transformations, including thundering it out fortissimo and turning into a lush cantabile. At the end, the motto theme emerges triumphant over hammer blows from the brass and percussion, the battle clearly won.
— Lawyer and lutenist Howard Posner has also annotated programs for the Los Angeles Baroque Orchestra and the Coleman Chamber Concerts. His notes have appeared in the program of the Salzburg Festival.
Length: 50 minutes
Orchestration: piccolo, three flutes, two oboes, English horn, two clarinets, bass clarinet, two bassoons, contrabassoon, four horns, three trumpets, three trombones, tuba, timpani, bass drum, snare drum, cymbals, two harps, and strings
First Los Angeles Philharmonic performance: July 29, 1926, Sir Henry Wood conducting


BlogsCan Chocolate Make You Slimmer?
New research hints at another potential health benefit of chocolate.
Chocolate continues to gain ground as a health food, this time as a way to stay slim while enjoying regular decadent snacks. Yes, regular. A new study found that people who ate chocolate a few times a week were leaner than those who ate it once in a while. The study, published in the Archives of Internal Medicine, compared the diet, chocolate intake, and body mass index of over 1,000 men and women. The researchers used BMI as an indicator of whether the participants were overweight or obese. Even when taking into account other factors, like exercise and total calories consumed, people who ate chocolate regularly had lower BMIs. While there was a connection between frequency and thinness, there was none for quantity. So it’s more important to eat chocolate throughout the week than to load up on King Size bars. Previous studies have shown that chocolate has many other health benefits. Eating chocolate can promote beneficial changes to your blood pressure and cholesterol levels, both of which are good for the heart. Chocolate, especially dark, also contains plentiful levels of antioxidants that neutralize damage done to cells by “free radicals.” The researchers are uncertain what aspect of chocolate promotes slender physiques, but suspect it is caused by catechins. These compounds have been shown to improve lean muscle mass and reduce weight in mice. Chocolate also contains caffeine, which can boost metabolism. This research, however, is not a free pass to binge on chocolate. Further research is needed to determine whether the health benefits of chocolate outweigh the additional calories consumed. Don’t be concerned about eating the occasional chocolate bar. If you are trying to lose weight, though, eating more fruits and vegetables is a better option.


Studies of Disorders With Increased Susceptibility to Fungal Infections
- Researchers are interested in studying disorders that make individuals more susceptible to fungal infections, specifically infections with the Candida yeast. These disorders are often related to problems with the immune system and may have genetic factors, which suggests that researchers should study not only the individual with the disorder, but also his or her first- and second-degree relatives (such as parents, siblings, children, and first cousins). To provide material for future research, individuals with immune disorders and their first- and second-degree relatives will be asked to provide blood and other samples for testing and comparison with samples taken from healthy volunteers with no history of immune disorders.
- To collect blood and other biological samples to study immune disorders that make individuals more susceptible to fungal infections.
- Individuals of any age who have abnormal immune function characterized by recurrent or unusual fungal infections, recurrent or chronic inflammation, or other types of immune dysfunction.
- First- or second-degree genetically related family members (limited to mother, father, siblings, grandparents, children, aunts, uncles, and first cousins).
- Healthy volunteers at least 18 years of age (for comparison purposes).
- Participants will provide blood samples and buccal (cells from the inside of the mouth near the cheek) samples.
- Participants with immune disorders will also be asked to provide urine samples, saliva or mucosal samples, or skin tissue biopsies, and may also have imaging studies (such as x-rays) to collect information for research.
- Samples may be collected at the National Institutes of Health or at other clinical locations for the samples to the sent to the National Institutes of Health.
- No treatment will be provided as part of this protocol....
Primary Immune Deficiency
Autoimmune Polyendocrinopathy Candidiasis Ectodermal
Chronic Mucocutaneous Candidiasis (CMC)
|Study Design:||Time Perspective: Prospective|
|Official Title:||Studies of Disorders With Increased Susceptibility to Fungal Infections|
|Study Start Date:||September 2010|
This study is designed for the evaluation, diagnosis, and long-term follow up of selected patients with primary immune deficiencies and other conditions associated with fungal, and more specifically with Candida spp. infections. The primary immune deficiencies to be studied include, but are not limited to, autoimmune polyendocrinopathy candidiasis ectodermal dystrophy (APECED), chronic mucocutaneous candidiasis (CMC), myeloperoxidase deficiency (MPO), immune dysregulation polyendocrinopathy enteropathy X-linked (IPEX), Job's syndrome, chronic granulomatous disease (CGD), and biotinidase deficiency. Diabetic patients and infants also show increased susceptibility to such infections and might be studied. Patient participants (who we will refer to as patients in this study) will undergo evaluations that include history/physical, blood sampling, genetic testing, and possible tissue sampling. We may use some of the blood cells to investigate the utility of induced pluripotent stem cells (iPS) for immune cell derivation and targeted gene correction. First or second degree genetically related family members (limited to mother, father, siblings, grandparents, children, aunts, uncles, and first cousins of an affected patient and who we will refer to as relatives in this study) might also be screened for clinical, in vitro, and genetic correlates of immune abnormalities. Healthy volunteers will be enrolled as a source of control samples for research testing. Among the aims of this protocol are to better understand the genetic and pathophysiologic factors that lead to defects in host defense, and to use modern and evolving methods in molecular and cellular biology to elucidate the pathogenesis of this particular susceptibility. A better understanding of primary immunodeficiency could allow for the rational development of novel therapies for such diseases and to benefit future patients, but it might not benefit current patient participants directly. Routine follow-up may occur every 6 months -with evaluation and blood sampling. Under some circumstances, we may provide treatment that relates to the immune deficiency. These treatments will follow standard medical practice.
|Contact: Sandra Maxwell, R.N.||(301) email@example.com|
|Contact: Sergio D Rosenzweig, M.D.||(301) firstname.lastname@example.org|
|United States, Maryland|
|National Institutes of Health Clinical Center, 9000 Rockville Pike||Recruiting|
|Bethesda, Maryland, United States, 20892|
|Contact: For more information at the NIH Clinical Center contact Patient Recruitment and Public Liaison Office (PRPL) 800-411-1222 ext TTY8664111010 email@example.com|
|Principal Investigator:||Sergio D Rosenzweig, M.D.||National Institute of Allergy and Infectious Diseases (NIAID)|


A new report from the Institute for Women’s Policy Research shows that the pay gap between men and women increased between 2011 and 2012, leaving women making $163 less per week:
In 2012, the ratio of women’s to men’s median weekly full-time earnings was 80.9 percent, a decline of more than one percentage point since 2011 when the ratio was 82.2 percent. This corresponds to a weekly gender wage gap of 19.1 percent for 2012. Women’s median weekly earnings in 2012 were $691, a marginal decline compared to 2011; men’s median weekly earnings were $854, a marginal increase compared to 2011.
Another measure of the earnings gap, the ratio of women’s and men’s median annual earnings for full-time year-round workers, was 77.0 in 2011 (data for 2012 are not yet available), less than half of a percentage point lower than in 2010 and equal to the gap in 2009. (This means the annual gender wage gap for full-time year-round workers is 23 percent.)
As Bryce Covert noted at Forbes, “What’s particularly strange about this is that the wage gap typically narrows during a recession.” But women have been hammered by the hemorrhaging of public sector jobs that has occurred in the last few years, as states and the federal governments cut back significantly due to conservative insistence on austerity.
The wage gap between women and men persists even for high-paying jobs, and women are significantly more likely to work for the minimum wage. A woman’s total lifetime earnings lost to the pay gap could feed a family of four for 37 years.


The 65 ft tall interactive sculpture was created from wood from the 165 ft long schooner Wawona, which sailed from 1897 to 1947. It is connected to the museum at its top and bottom. © John Grade
The new sculpture at the Museum of History and Industry in Seattle required a great deal of structural analysis to ensure it can withstand seismic forces—and curious visitors.
January 29, 2013—It’s plain to see that turning the remains of a sailing schooner more than a century old into a 65 ft tall interactive sculpture for the Museum of History and Industry (MOHAI) in Seattle, required a great deal of artistic vision. But what might not be as obvious is the amount of structural analysis required to ensure the sculpture maintains its structural integrity under seismic forces and human-induced loads.
Dedicated to preserving and sharing the history of Seattle and the Puget Sound region, the MOHAI commissioned Seattle-based artist John Grade to create a sculpture for the museum’s new home: the renovated Naval Reserve Armory along the shore of Lake Union. Shortly after winning the commission, Grade was entrusted with the remains of the dismantled schooner Wawona.
Built by influential shipbuilder Hans Ditlev Bendixsen, the 165 ft long schooner Wawona sailed from 1897 to 1947, carrying lumber and, later, fish through Puget Sound. After it was decommissioned, the ship was on display until 2009, when it was disassembled. A great deal of the vessel’s wood had rotted significantly by that time, but much of the planking was in good condition despite having been under water all those years. Leaching from the ship’s wrought iron and temporary copper cladding and staining from the oils of the fish it once carried brought out a variety of colors within the wood, making it perfect for the sculpture, Grade said in written responses to questions posed by Civil Engineering online.
Named for the vessel from which the wood was derived, the 10,000 lb Wawona sculpture extends from the floor of the museum to its ceiling. Grade said the vertical orientation of the sculpture references the old-growth trees that once covered the landscape near the museum. Its tapered shape—roughly 10 ft in diameter at its base and approximately 4 ft in diameter at its top— recalls a ship’s hull, he said. To further connect it to the natural world, the sculpture penetrates the museum’s floor and ceiling, enabling visitors who walk within the hollow form to see the lake below and the sky above, Grade explained.
Creating such a large sculpture required a great deal of engineering expertise. Grade worked with the Seattle office of Arup, an international engineering firm headquartered in London, to turn his vision into a reality. “Arup provided structural engineering services, starting at concepts ... on through artwork permitting, construction documents, and construction administration,” said Hans-Erik Blomgren, P.E., P.Eng., M.ASCE, the project manager for Arup, in written responses to questions from Civil Engineering online. “Interactive artwork of this scale, weight, and permanence requires it to be treated as an element and component of the building from a code standpoint.”
Artist John Grade wanted visitors to be able to walk within the
sculpture, to be able to view the lake below and the sky above, and
to be able to touch and push on the sculpture without damaging it.
© John Grade
But before they began getting into the details of the structural design, Arup’s engineers suggested using digital technology to fabricate the components of the sculpture. As a result, Grade engaged the University of Washington College of the Built Environments to individually cut the sculpture’s more than 200 wooden pieces using computer numerical control (CNC) fabrication. The CNC technology was also used to fashion the steel hangers and rods that hold the sculpture’s wooden components together horizontally and vertically. The digital fabrication plans were developed parallel with the structural design.
Arup had several performance objectives for the project, including ensuring that the sculpture could endure human-induced movement, resist metal fatigue under cyclic motion, and withstand seismic forces. The team also had to ensure that the wood was kiln dried to the correct moisture content and that the sculpture would hang vertically through its center of mass over the correct location on the museum’s floor, Blomgren said.
To meet these objectives, Arup and the team from the college used Rhino 3D and a parametric plug-in tool known as Grasshopper (both produced by Seattle-based Robert McNeel & Associates) to model each of the sculpture’s steel and wooden components for fabrication and structural analysis. They then exported a wireframe model from the Rhino files into another program that enabled them to analyze the sculpture under its own weight, seismic forces, and human-induced loads, Blomgren said.
For the seismic forces, the team treated the sculpture as an element and component as defined in ASCE Standard 7-05 (Minimum Design Loads for Buildings and Other Structures, ASCE, Reston, Virginia, 2006.) “We then applied an equivalent static force in orthogonal directions,” Blomgren said. On the basis of the analysis, the team added rubber damper restraints at the base of the sculpture to provide lateral support under seismic loads and make the sculpture flexible between the floor and the ceiling, Blomgren said.
Arup engineers used computer numerical control techniques to
fabricate the more than 200 wooden pieces that form the sculpture
as well as the steel hangers and rods that hold those wooden
components together. © Arup
The human-induced forces were studied as a 200 lb force at a height of roughly 4 ft from the sculpture’s base. “We wanted to be sure the wooden planks supporting this concentrated load were sufficient,” Blomgren explained. As a result of the analysis, the team included a steel rod that extends from the underside of the sculpture to approximately 10 in. below the floor. This rod is allowed to articulate but a viscoelastic polymer disk provides resistance to quickly dampen human-induced oscillation, Blomgren said. “It was important to me that people directly, physically interact with the sculpture,” Grade explained. “I wanted it to have enough flex that a small child could push the base of the sculpture into movement but that movement would stop quickly and not endanger other people simultaneously interacting with the sculpture.”
Following 20 months of design, the Wawona sculpture was unveiled when the MOHAI opened at its new location on December 29, 2012. “The MOHAI is a fantastic and rich place full of cherished Seattle artifacts,” Blomgren said. “The Wawona sculpture, however, stands apart as something distinct because it is a new creation that employs state-of-the-art design but is richly and brilliantly tied to the Pacific Northwest’s history of shipbuilding, fishing, and old-growth forests.”


I mentioned Wolbachia in my parthenogenesis post; here I will talk about it in more detail, because it’s a really cool parasite, as well as in the center of much research nowadays.
Wolbachia are Gram-negative ⍺-Proteobacteria (order Rickettsiales, family Anaplasmataceae; Dumler et al.,2001), systematically split into 6 supergroups, lettered from A to F (Lo et al., 2002). Those in supergroups C and D have coevolved with their nematodan hosts and are mutualistic (Bandi et al., 1998). Those in supergroups A and B are parasites in arthropods. Morphologically, they come in two groups: ~1µm large rods, and ~0.5µm diameter coccoids. They can be found in a membrane-bound vacuole in the host cell’s cytoplasm (Yen & Barr, 1971); in arthropods, this will be in egg and ovarian cells (see diagram above, from Weiss et al. (2009)), although it has also been found in other tissues, including the Malpighian tubules, and muscle and nervous tissue (Stouthamer et al., 1999). When found in sperm cell cytoplasm, it disappears during spermatogenesis (Clark et al., 2002).
Note that in this post and in the literature, what’s referred to as Wolbachia is Wolbachia pipientis. Before DNA sequencing, when bacteria were classified morphologically, W. persica and W. melaphagi were also thought to be related, but these have nothing to do with the famous Wolbachia (W. persica is a γ-proteobacterium, W. melaphagi is a rhizobacterium).
Being present endosymbiotically in 20+% of all known insect species (Werren & Windsor, 2000), and given that some estimate that over half of all insect species are infected by it (Hilgenboecker et al., 2008), it’s obviously extremely successful, although it should be noted that the virulence of each Wolbachia strain is different (Min & Benzer, 1997), and each species is has a different susceptibility. In Australian and Panamanian fig wasps, Wolbachia has been found to infect over 70% of all species (Haine & Cook, 2005). A host database can be found here.
The biggest reason for its success is its parasitic effect: it’s always transferred maternally in the cytoplasm of the eggs, and in order to ensure maximal transfer rates, it alters its host’s reproductive abilities to favour their own reproductive success (Charlat et al., 2003). It has four ways to do this, in contrast to the one or two ways present in other such parasites:
- Inducing thelytokous parthenogenesis in haplodiploid organisms, e.g. hymenopterans, thus making sure that only female offspring are produced (e.g. Stouthamer et al., 1993). It occurs by forcing the fusion of the two nuclei of the first mitotic division (Huigens et al., 2000).
- Feminizing males, i.e. males reproduce as females (Wilkinson, 1998). The mechanism for this varies; for example, in the pillbug, Wolbachia blocks the formation of the androgenic gland which produces the masculinising androgenic hormone (Martin et al., 1990).
- Killing males, either in the embryonic stages or later (Hurst, 1991). The mechanisms of action are still largely unknown, although recent pioneering research by Riparbelli et al. (2012) shows that it happens due to Wolbachia (purposely?) messing around with male chromosomes at various stages in development, leading to defective embryos and death.
- Inducing cytoplasmic incompatibility (CI) between infected males and uninfected females (Hurst & Werren, 2001), causing sterility (Bordenstein & Werren, 2007) and eventually reproductive isolation within a species.
The latter was the first of Wolbachia‘s effects to be discovered, by Yen & Barr (1971) in mosquitoes; Wolbachia itself was first spotted by Hertig & Wolbach (1924). What happens is that the sperm enters the cell as normal, but its chromosomes don’t decondense and fuse with maternal chromosomes due to a delay in the breakdown of the nuclear envelope in the male’s pronucleus (Tram & Sullivan (2002); see Landmann et al. (2009) for more molecular details), and so can’t enter the first mitosis, meaning they get discarded (Lassy & Karr, 1996). The embryo either becomes a haploid female (in haplodiploid organisms), or it dies. In evolutionary theory terms, in a population susceptible to Wolbachia-induced CI, uninfected females become more unfit, therefore giving a fitness advantage to infected females (Bourtzis et al., 2003), hence explaining how the phenotype persists.
Which manipulation happens cannot be predicted even within the same species, as demonstrated by Hornett et al. (2008), who found that in their North American Hypolimnas bolina butterflies, Wolbachia was a male killer while in Southeast Asian ones, it was a CI-inducer. The difference came from a dominant allele in the SE Asian butterfly genome suppressing the male-killing. Charlat et al. (2007) showed that such a mutation can become fixed in a population in under 10 generations due to the extreme selection pressure to maintain a decent sex ratio, a testament to the ecological power of Wolbachia.
However, in some cases, Wolbachia can be so prominent that the entire affected population gets a very female-biased sex ratio, which in the case of the butterfly Acarea encedon has led to females reversing their sexual roles and behaving like males (Jiggins et al., 2000). In other cases, Wolbachia is counteracted by other elements, for example the B chromosome in the parasitoid wasp Trichogramma kaykai which turns Wolbachia-feminised males back into regular males (Stouthamer et al., 2001).
It must be mentioned that part of their success is their ability to be transmitted horizontally across different species (Raychoudhury et al., 2009) – they aren’t host-specific. This has been shown as happening through parasitoids (Heath et al., 1999) or through the environment (e.g. by sharing a common food source (Huigens et al., 2000)). This also means that a single individual may have multiple Wolbachia species (or, better said, strains) co-existing and mingling inside it; the largest number I know of is eight, in the fire ant Solenopsis daguerrei (Dedeine et al., 2005). Note that this ability only comes in the arthropod-associated Wolbachia, whose genomes are more plastic, with recombination and phage-derived elements (Wu et al., 2004), none of which are characteristics present in their nematodan counterparts (Foster et al., 2005).
One study also reported the possibility of Wolbachia having transferred part or all of its genome to its hosts, albeit with only 2% of the genes able to be transcribed and none of them having any described effect (Hotopp et al., 2007).
The negative effects of Wolbachia are obviously of great interest for biocontrol of pests and disease vectors. For example, Alam et al. (2011) discuss the possibility of using Wolbachia to control the tsetse fly, a vector of trypanosomiasis; Atyame et al. (2011) do the same for mosquitoes. Such biocontrol would work by allowing a chosen genotype to dominate the population by infecting the undesired genotype (e.g. Xi et al. (2005)), or by shortening lifespans to prevent sexual maturity (e.g. Moreira et al. (2009)). Wolbachia can also lead to population bottlenecks with very few individuals becoming able to reproduce (Nice et al., 2009), which is another way to control a pest population.
In non-pest studies, Wolbachia leads to increased susceptibility to parasitoids in Drosophila (Fytrou et al., 2006). It also leads to a less effective immune system in the pillbug Armadillidum vulgare, as seen by a lower density of haemocytes and higher density of bacteria (Bracquart-Vanier et al., 2008). These would be other avenues for pest control if a similar effect is seen in pest groups.
Positive Effects of Wolbachia
Interestingly, the effects of Wolbachia aren’t all negative. In the Cimicidae (bed bugs), Wolbachia is a mutualist; getting rid of it with antibiotics reduces the amount of food the host gets (Hosokawa et al., 2010). In mosquitoes, Wolbachia was found to boost their immune system and cause resistance to dengue virus (Bian et al., 2010). Pinto et al. (2012) describe how this happens at the genetic level. This is another potential use of Wolbachia as a biocontrol agent for disease vectors. In Drosophila, Wolbachia has been shown to confer resistance to several RNA viruses (Teixeira et al., 2008). In a Drosophila lab culture, Weeks et al. (2007) showed that the Wolbachia went from being a parasite to being a mutualist within two decades.
At the extreme end, nematode-infecting Wolbachia are needed for nematode development and fertility (Foster et al., 2005), so Wolbachia antibiotics could be used to control their populations (Taylor & Hoerauf, 1999). This is useful knowledge, given that some of the affected nematodes are vectors for very serious diseases like elephantiasis and onchocerciasis. It’s a similar story with the wasp Asobara tabida, wherein no ovocyte can even be produced when Wolbachia isn’t present (Dedeine et al., 2001) because its absence promotes excessive apoptosis in the ovarioles (Pannebakker et al., 2007).
Other effects of Wolbachia on sexual physiology have been documented, for example an increase in sperm competition in Tribolium beetles (Wade & Chang, 1995), or changes to the spermathecal duct in female Allonemobius crickets (Marshall, 2007).
An interesting point can be made about the process of molecular evolution in Wolbachia. As I said in the introductory paragraph, Wolbachia is a nematode mutualist and arthropod parasite (generally speaking). One of the Wolbachia genes involved in interaction with the host is wsp, which codes for cell membrane proteins. It was found to be undergoing divergent selection when it is in a parasitic relationship, but not when it’s in a mutualistic relationship (Jiggins et al., 2002). This is in line with what we expect: wsp being involved in host recognition means it theoretically should experience heightened evolutionary rates, and this is confirmed by the empirical data.
Many, if not all, negative and positive effects of Wolbachia have evolved by natural selection in order to maximise the transmission of the strain, either by allowing the bacterium to survive in the host (depressed immune system), or reducing competition by blocking the transmission of other pathogens (as Teixeira et al. (2008) suggest for the viral resistance effect). By extension, this means that parthenogenic arthropods aren’t expected to be Wolbachia hosts, since the manipulations are useless there. In terms of evolutionary theory, they can be treated as nothing more than selfish genetic elements.
When I first heard of Wolbachia, my intuition was that it played a sizeable role in speciation, since it promotes reproductive isolation, or by selecting for subdivided populations (Hatcher et al., 2000). Some analyses showed it not to be true (Rousset & Raymond, 1991), but more and more recent studies are supportive of the idea (Bordenstein, 2003), so it’s accepted as a cause of speciation. It definitely has been demonstrated (Thompson, 1987), and in some cases has also induced rapid speciation (Bordenstein et al., 2001).
On a general evolutionary synthesis level, Wolbachia is pretty interesting as a very recognisable case of inheritable symbiosis, one of the few proper examples that lend credence to the view that symbioses are a driving force behind evolution.
Milder effects of large-scale Wolbachia infection and sex ratio-skewing include altering dispersal ability – many insects have dispersing females and non-dispersing males, or vice versa. On a more influential level, there is also evidence that they can play a role in sexual selection (Jiggins et al., 2000), since sexual conflict gets reduced when levels of polyandry fall (Arnqvist & Rowe, 2005).
Wolbachia can sometimes present a methodological stumbling block for molecular phylogenies based on mitochondrial DNA, since mtDNA will also hitchike maternally, favouring the maternal mtDNA haplotype, eventually leading to the entire dataset being worthless; see Ballard & Rand (2005) for more information. However, Arthofer et al. (2010) tested this idea using infected bark beetles and found no significant effect from Wolbachia, so it is still unsure just how significant this slight inaccuracy is.
Where it is definitely a problem is in barcoding initiatives using mtDNA. For successful barcoding of a species, a stable molecular marker needs to be used that is guaranteed not to vary across individuals, populations, or ecomorphs. However, there are some studies that show that Wolbachia causes divergences in mtDNA sequences even among individuals of the same species, e.g. in the butterfly genus Hypolimnas (Galtier et al., 2009). The reason for this is that mitochondrial genes are transferred only maternally, so only the maternal set plays a role in evolution. Given the ubiquity of Wolbachia, this is definitely a large problem that should be studied carefully before proceeding with mtDNA barcoding.
Wolbachia alone can’t be cultivated, but it is possible to keep a Wolbachia line using host cell lines (Noda et al., 2002), so experimental evolution studies are possible with them.
For the entomologists among you, make sure to check any colonies for Wolbachia infections, as they could invalidate your results, especially if you’re doing population biology. They can be gotten rid of using any antibiotic. I hear that tetracycline is recommended; if that’s not possible, high heat is enough, since Wolbachia is sensitive to temperature. If you’re sequencing your insects as well, using DNA from the legs is probably the safest way to avoid getting contaminating Wolbachia DNA amplified (this is standard procedure anyway).
Other symbionts that alter the reproduction of their arthropod hosts include Buchnera and Cardinium – but I’ll leave them for other posts.
Alam U, Medlock J, Breisfoard C, Pais R, Lohs C, Balmand S, Carnogursky J, Heddi A, Takac P, Galvani A & Aksoy S. 2011. Wolbachia Symbiont Infections Induce Strong Cytoplasmic Incompatibility in the Tsetse Fly Glossina morsitans. PLoS Pathogens 7, e1002415.
Arnqvist G & Rowe L. 2005. Sexual Conflict.
Arthofer W, Avtzis DN, Riegler M & Stauffer C. 2010. Mitochondrial phylogenies in the light of pseudogenes and Wolbachia: re-assessment of a bark beetle dataset. ZooKeys 56, 269-280.
Atyame CM, Pasteur N, Dumas E, Tortosa P, Tantely ML, Pocquet N, Licciardi S, Bheecarry A, Zumbo B, Weill M & Duron O. 2011. Cytoplasmic Incompatibility as a Means of Controlling Culex pipiens quinquefasciatus Mosquito in the Islands of the South-Western Indian Ocean. PLoS Neglected Tropical Diseases 5, e1440.
Ballard JWO & Rand DM. 2005. The population biology of mitochondrial DNA and its phylogenetic implications. Annual Review of Ecology, Evolution, and Systematics 36, 621-642.
Bandi C, Anderson TJC, Genchi C & Blaxter ML. 1998. Phylogeny of Wolbachia in Filarial Nematodes. Proc. R. Soc. B 265, 2407-2413.
Bian G, Xu Y, Lu P, Xie Y & Xi Z. 2010. The Endosymbiotic Bacterium Wolbachia Induces Resistance to Dengue Virus in Aedes aegypti. PLoS Pathogens 6, e1000833.
Bordenstein SR. 2003. Symbiosis and the origin of species. In: Bourtzis K & Miller TA (eds.). Insect Symbiosis, Vol. 1.
Bordenstein SR & Werren JH. 2007. Bidirectional incompatibility among divergent Wolbachia and incompatibility level differences among closely related Wolbachia in Nasonia. Heredity 99, 278-287.
Bordenstein SR, O’Hera FP & Werren JH. 2001. Wolbachia- induced incompatibility precedes other hybrid incompatibility in Nasonia. Nature 409, 707-710.
Bourtzis K, Braig HR & Karr TL. 2003. Cytoplasmic incompatibility. In: Bourtzis K & Miller TM (eds). Insect Symbiosis.
Bracquart-Vanier C, Lachat M, Herbinière J, Johnson M, Caubet Y, Bouchon D & Sicard M. 2008. Wolbachia media variation in host immunocompetence. PLoS ONE 3, e3286.
Charlat S, Hurst GDD, Merçot H. 2003. Evolutionary consequences of Wolbachia infections. Trends in Genetics 19, 217-223.
Charlat S, Hornett EA, Fullard JH, Davies N, Roderick GK, Wedell N & Hurst GDD. 2007. Extraordinary Flux in Sex Ratio. Science 317, 214.
Clark ME, Veneti Z, Bourtzis K & Karr TL. 2002. The distribution and proliferation of the intracellular bacteria Wolbachia during spermatogenesis in Drosophila. Mechanisms of Development 111, 3-15.
Dedeine F, Vavre F, Fleury F, Loppin B, Hochberg ME & Boulétreau M. 2001. Removing symbiotic Wolbachia bacteria specifically inhibits oogenesis in a parasitic wasp. PNAS 98, 6247-6252.
Dedeine F, Ahrens M, Calcaterra L, Shoemaker DD. 2005. Social parasitism in fire ants (Solenopsisspp.): a potential mechanism for interspecies transfer of Wolbachia. Molecular Ecology 14, 1543-1548.
Dumler JS, Barbet AF, Bekker CP, Dasch GA, Palmer GH, Ray SC, Rikihisa Y & Rurangirwa FR. 2001. Reorganization of genera in the families Rickettsiaceae and Anaplasmataceae in the order Rickettsiales: unification of some species of Ehrlichia with Anaplasma, Cowdria with Ehrlichia and Ehrlichia with Neorickettsia, descriptions of six new species combinations and designation of Ehrlichia equi and ‘HGE agent’ as subjective synonyms of Ehrlichia phagocytophila. International Journal of Systematic and Evolutionary Microbiology 51, 2145-2165.
Foster J, Ganatra M, Kamal I, Ware J, Makarova K, Ivanova N, Bhattachryya A, Kapatral V, Kumar S, Posfai J, Vincze T, Ingram J, Moran L, Lapidus A, Omelchenko M, Kyprides N, Ghedin E, Wang S, Goltsman E, Joukov V, Ostrovskaya O, Tsukerman K, Mazur M, Comb D, Koonin E & Slatko B. 2005. The Wolbachia Genome of Brugia malayi: Endosymbiont Evolution within a Human Pathogenic Nematode. PLoS Biology 3, e121.
Fytrou A, Schofield PG, Kraaljeveld AR & Hubbard SF. 2006. Wolbachia infection suppresses both host defence and parasitoid counter-defence. Proc. R. Soc. B 273, 791-796.
Galtier N, Nabholz B, Glémin S & Hurst GDD. 2009. Mitochondrial DNA as a marker of molecular diversity: a reappraisal. Molecular Ecology 18, 4541-4550.
Haine ER & Cook JM. 2005. Convergent incidences of Wolbachia infection in fig wasp communities from two continents. Proc. R. Soc. B 272, 421-429.
Hatcher MJ, Dunn AM & Tofts C. 2000. Co-existence of hosts and sex ratio distorters in structured populations. Evolutionary Ecology Research 2, 185-205.
Heath BD, Butcher RDJ, Whitfield WGF & Hubbard SF. 1999. Horizontal transfer of Wolbachia between phylogenetically distant insect species by a naturally occurring mechanism. Current Biology 9, 313-316.
Hertig M & Wolbach SB. 1924. Studies on Rickettsia-Like Micro-Organisms in Insects. Journal of Medical Research 44, 329-374.
Hilgenboecker K, Hammerstein P, Schlatmann P, Telschow A & Werren JH. 2008. How many species are infected with Wolbachia? – a statistical analysis of current data. FEMS Microbiology Letters 281, 215-220.
Hornett EA, Duplouy AM, Davies N, Roderick GK, Wedell N, Hurst GDD & Charlat S. 2008. YOU CAN’T KEEP A GOOD PARASITE DOWN: EVOLUTION OF A MALE-KILLER SUPPRESSOR UNCOVERS CYTOPLASMIC INCOMPATIBILITY. Evolution 62, 1258-1263.
Hosokawa T, Koga R, Kikuchi Y, Meng X-Y & Fukatsu T. 2010. Wolbachia as a bacteriocyte-associated nutritional mutualist. PNAS 107, 769-774.
Hotopp JCD, Clark ME, Oliveira DCSG, Foster JM, Fischer P, Torres MCM, Giebel JD, Kumar N, Ishmael N, Wang S, Ingram J, Nene RV, Shepard J, Tomkins J, Richards S, Spiro DJ, Ghedin E, Slatko BE, Tettelin HE & Werren JH. 2007. Widespread Lateral Gene Transfer from Intracellular Bacteria to Multicellular Eukaryotes. Science 317, 1753-1756.
Huigens ME, Luck RF, Klaassen RHG, Maas MFPM, Timmermans MJTM & Stouthamer R. 2000. Infectious parthenogenesis. Nature 405, 178-179.
Hurst LD. 1991. The Incidences and Evolution of Cytoplasmic Male Killers. Proc. R. Soc. B 244, 91-99.
Hurst GDD & Werren JH. 2001. The role of selfish genetic elements in eukaryotic evolution. Nature Reviews Genetics 2, 597-606.
Jiggins FM, Hurst GDD & Majerus MEN. 2000. Sex-ratio-distorting Wolbachia causes sex-role reversal in its butterfly host. Proc. R. Soc. B 267, 69-73.
Jiggins FM, Hurst GDD & Yang Z. 2002. Host-Symbiont Conflicts: Positive Selection on an Outer Membrane Protein of Parasitic but not Mutualistic Rickettsiaceae. Molecular Biology and Evolution 19, 1341-1349.
Landmann F, Orsi GA, Loppin B & Sullivan W. 2009. Wolbachia-Mediated Cytoplasmic Incompatibility Is Associated with Impaired Histone Deposition in the Male Pronucleus. PLoS Pathogens 5, e1000343.
Lassy CW & Karr TL. 1996. Cytological analysis of fertilization and early embryonic development in incompatible crosses of Drosophila simulans. Mechanisms of Development 57, 47-58.
Lo N, Casiraghi M, Salati E, Bazzocchi C & Bandi C. 2002. How Many Wolbachia Supergroups Exist? Molecular Biology and Evolution 19, 341-346.
Marshall JL. 2007. Rapid evolution of spermathecal duct length in the Allonemobius socius complex of crickets: species, population and Wolbachia effects. PLoS ONE 2, e720.
Martin G, Juchault P, Sorokine O & van Dorsselaer. 1990. Purification and characterization of androgenic hormone from the terrestrial isopod Armadillidium vulgare Latr. (Crustacea, Oniscidea). General and Comparative Endocrinology 80, 349-354.
Min K-T & Benzer S. 1997. Wolbachia, normally a symbiont of Drosophila, can be virulent, causing degeneration and early death. PNAS 94, 10792-10796.
Moreira LA, Iturbe-Ormaetxe I, Jeffery JA, Lu G, Pyke AT, Hedges LM, Rocha BC, Hall-Mendelin S, Day A, Riegler M, Hugo LE, Johnson KN, Kay BH, McGraw EA, van den Hurk AF, Ryan PA & O’Neill SL. 2009. A Wolbachia Symbiont in Aedes aegypti Limits Infection with Dengue, Chikungunya, and Plasmodium. Cell 139, 1268-1278.
Nice CC, Gompert Z, Forister ML & Fordyce JA. 2009. An unseen foe in arthropod conservation efforts: the case of Wolbachia infections in the Karner blue butterﬂy. Biological Conservation 142, 3137-3146.
Noda H, Miyoshi T & Koizumi Y. 2002. In vitro cultivation of Wolbachia in insect and mammalian cell lines. In Vitro Cellular & Developmental Biology – Animal 38, 423-427.
Pannebakker BA, Loppin B, Elemans CPH, Humblot L & Vavre F. 2007. Parasitic inhibition of cell death facilitates symbiosis. PNAS 104, 213-215.
Pinto SB, Mariconti M, Bazzocchi C, Bandi C & Sinkins SP. 2012. Wolbachia surface protein induces innate immune responses in mosquito cells. BMC Microbiology 12 (Suppl. 1), S11.
Raychoudhury R, Baldo L, Oliveira DCSG & Werren JH. 2009. Modes of acquisition of Wolbachia: horizontal transfer, hybrid introgression, and codivergence in the Nasonia species complex. Evolution 63, 165-183.
Riparbelli MG, Giordano R, Ueyama M & Callaini G. 2012. Wolbachia-Mediated Male Killing Is Associated with Defective Chromatin Remodeling. PLoS ONE 7, e30045.
Rousset F & Raymond M. 1991. Cytoplasmic incompatibility in insects: Why sterilize females? TrEE 6, 54-57.
Stouthamer R, Breeuwer JAJ, Luck RF & Werren JH. 1993. Molecular identification of microorganisms associated with parthenogenesis. Nature 361, 66-68.
Stouthamer R, Breeuwer JAJ, Hurst GDD. 1999. WOLBACHIA PIPIENTIS: Microbial Manipulator of Arthropod Reproduction. Annual Review of Microbiology 53, 71-102.
Stouthamer R, van Tilborg M, de Jong JH, Nunney L & Luck RF. 2001. Selfish element maintains sex in natural populations of a parasitoid wasp. Proc. R. Soc. B 268, 617-622.
Taylor MJ & Hoerauf A. 1999. Wolbachia Bacteria of Filarial Nematodes. Parasitology Today 15, 437-442.
Teixeira L, Ferreira Á & Ashburner M. 2008. The Bacterial Symbiont Wolbachia Induces Resistance to RNA Viral Infections in Drosophila melanogaster. PLoS Biology 6, e1000002.
Thompson JN. 1987. Symbiont induced speciation. Biological Journal of the Linnean Society 32, 385-393.
Tram U & Sullivan W. 2002. Role of delayed nuclear envelope breakdown and mitosis in Wolbachia-induced cytoplasmic incompatibility. Science 296, 1124-1126.
Wade MJ & Chang NW. 1995. Increased male fertility in Tribolium confusum beetles after infection with the intracellular parasite Wolbachia. Nature 373, 72-74.
Weeks AR, Turelli M, Harcombe WR, Reynolds KT & Hoffmann AA. 2007. From Parasite to Mutualist: Rapid Evolution of Wolbachia in Natural Populations of Drosophila. PLoS Biology 5, e114.
Weiss BL, Attardo GM & Aksoy S. 2009. Insect–Protozoa–Bacteria Associations: a Model System for Investigating Host–Parasite Interactions. In: Stock SP, Vandenberg J, Glazer I & Boemare N. Insect Pathogens: Molecular Approaches and Techniques, pp. 223-240.
Werren JH & Windsor DM. 2000. Wolbachia infection frequencies in insects: evidence of a global equilibrium? Proc. R. Soc. B 267, 1277-1285.
Wilkinson T. 1998. Wolbachia come of age. Trends in Ecology & Evolution 13, 213-214.
Wu M, Sun LV, Vamathevan J, Riegler M, Deboy R, Brownile JC, McGraw EA, Martin W, Esser C, Ahmadinejad N, Wiegand C, Madupu R, Beanan MJ, Brinkac LM, Daugherty SC, Durkin AC, Kolonay JF, Nelson WC, Mohamoud Y, Lee P, Berry K, Young MB, Utterback T, Weidman J, Nierman WC, Paulsen IT, Nelson KE, Tettelin H, O’Neill SL & Eisen JA. 2004. Phylogenomics of the Reproductive Parasite Wolbachia pipientis wMel: A Streamlined Genome Overrun by Mobile Genetic Elements. PLoS Biology 2, e69.
Xi Z, Dean JL, Khoo C & Dobson SL. 2005. Generation of a novel Wolbachia infection in Aedes albopictus (Asian tiger mosquito) via embryonic microinjection. Insect Biochemistry and Molecular Biology 35, 903-910.
Yen JH & Barr AR. 1971. New Hypothesis of the Cause of Cytoplasmic Incompatibility in Culex pipiens L. Nature 232, 657-658.
Research Blogging necessities :)
R. Stouthamer, J. A. J. Breeuwer, & G. D. D. Hurst (1999). WOLBACHIA PIPIENTIS: Microbial Manipulator of Arthropod Reproduction Annual Review of Microbiology DOI: 10.1146/annurev.micro.53.1.71


86 is conjectured to be the largest power of 2 not containing a zero. This simply stated conjecture has proven itself to be proof-resistant. Let us see why.
What is the probability that the nth power of two will not have any zeroes? The first and the last digits are non-zeroes; suppose that other digits become zeroes randomly and independently of each other. This supposition allows us to estimate the probability of 2n not having zeroes as (9/10)k-2, where k is the number of digits of 2n. The number of digits can be estimated as n log102. Thus, the probability is about cxn, where c = (10/9)2 ≈ 1.2 and x = (9/10)log102 ≈ 0.97. The expected number of powers of 2 without zeroes starting from the power N is cxN/(1-x) ≈ 40 ⋅ 0.97N.
Let us look at A007377, the sequence of numbers such that their powers of 2 do not contain zeros: 1, 2, 3, 4, 5, 6, 7, 8, 9, 13, 14, 15, 16, 18, 19, 24, 25, 27, 28, 31, 32, 33, 34, 35, 36, 37, 39, 49, 51, 67, 72, 76, 77, 81, 86. Our estimates predicts 32 members of this sequence starting from 6. In fact, the sequence has 30 conjectured members. Similarly, our estimate predicts 2.5 members starting from 86. It is easy to check that the sequence doesn’t contain any more numbers below 200 and our estimate predicts 0.07 members after 200. As we continue checking larger numbers and see that they do not belong to the sequence, the probability that the sequence contains more elements vanishes. With time we check more numbers and become more convinced that the conjecture is true. Currently, it has been checked up to the power 4.6 ⋅ 107. The probability of finding something after that is about 1.764342396 ⋅10-633620.
Let us try to approach the conjecture from another angle. Let us check the last K digits of powers of two. As the number of possibilities is finite, these last digits eventually will start cycling. If we can show that all the elements inside the period contain zeroes, then we need to check the finite number of powers of two until this period starts. If we can find such K, we can prove the conjecture.
Let us look at the last two digits of powers of two. The sequence starts as: 01, 02, 04, 08, 16, 32, 64, 28, 56, 12, 24, 48, 96, 92, 84, 68, 36, 72, 44, 88, 76, 52, 04. As we would anticipate, it starts cycling. The cycle length is 20, and 90% of numbers in the cycle don’t have zeroes.
Now let’s continue to the last three digits. The period length is 100, and 19 of them either start with zero or contain zero. The percentage of elements in the cycle that do not contain zero is 81%.
The cycle length for the last n digits is known. It is 4 ⋅ 5n-1. In particular the cycle length grows by 5 every time. The number of zero-free elements in these cycles form a sequence A181610: 4, 18, 81, 364, 1638, 7371, 33170. If we continue with our supposition that the digits are random, and study the new digits that appear when we move from the cycle of the last n digits to the next cycle of the last n+1 digits, we can expect that 9/10 of those digits will be non-zero. Indeed, if we check the ratio of how many numbers do not contain zero in the next cycle compared to the previous cycle, we get: 4.5, 4.5, 4.49383, 4.5, 4.5, 4.50007. All of these numbers are quite close to our estimation of 4.5. If this trend continues the portion of the numbers in the cycle that don’t have zeroes tends to zero; however, the total of such numbers grows exponentially. We can even estimate that the expected growth is 4 ⋅ 4.5n-1. From this estimation, we can derive the conjecture:
Conjecture. For any number N, there exists a power of two such that its last N digits are zero-free.
Indeed, the last N digits of powers of two cycle, and there are an increasing number of members inside that cycle that do not contain zeroes. The corresponding powers of two don’t have zeroes among N rightmost digits.
So, how do we combine the two results? First, the expected probability of finding the power of two larger than 86 that doesn’t contain zero is minuscule. And second, we most certainly can find a power of two that has as many zeroless digits at the end as we want.
To combine the two results, let us look at the sequences A031140 and A031141. We can deduce from them that for the power 103233492954 the first zero from the right occupies the 250th spot. The total number of digits of that power is 31076377936. So 250 is a tiny portion of the digits.
As time goes by we grow more and more convinced that 86 is the largest power of two without zeroes, but it is not at all clear how we can prove the conjecture or whether it can be proven at all.
My son, Sergei, suggested that I claim that I have a proof of this conjecture, but do not have enough space in the margin to fit my proof in. The probability that I will ever be shamed and disproven is lower than the probability of me winning a billion dollars in the lottery. Though then, if I do win the big bucks, I will still care about being shamed and disproven.


I have been trying to consolidate my beliefs and understandings about practice the last few weeks. As the mother of a hockey player and two dancers I am all too familiar with the idea of practice in sport. In their activities my children have the opportunity to work on isolated skills repeatedly until they become fluid, efficient and second nature. Their coaches are constantly giving them feedback, modelling and helping them get the “feel” for their sport. These practiced skills are constantly being put into use…be it a game or a dance. It is in those game situations where I really see my kids light up. They love to play, perform and just plain have FUN!! In those moments all of the practice becomes worth it and it is in those moments they become reenergize for and reinvested in further practice.
It is with this notion of practice in my head that I began to explore what practice is in education. How it is like practice in sport? I do believe that practice is important in both sport and students learning, but I also believe that not all practice is created equal. Some practice can support learning, consolidate understanding and build confidence for students while other practice can frustrate, confuse and create a barrier for learning. Practice can make “perfect” or at least better but it can also make permanent…and if the practice isn’t effective we run the risk of making permanent misconceptions.
But what is “perfect” practice? Can “perfect” practice really exist? I do not think that “perfect” is an attainable goal but I do think that purposeful is. Purposeful practice implies that teachers and coaches have an aim…intent…goal…target for the practice they want students to engage in. They identify a student/player need, envision what success would look like and with those things in mind create a plan to support the learning with practice. Purposeful practice takes careful thinking into the what, how and why of the practice with the goal of furthering individual students’ learning in ways that are the most meaningful. It is more than just practice for practice sake, more than a stack of worksheets for all students to complete…it is practice with purpose, practice that is deliberate, powerful and focused. The thing that I think we as teachers need to remember and that coaches do so well, is to put the practice into the game. After all it is in the game where the FUN is.
As I continue to think about Purposeful Practice I am consolidating my beliefs into what it truly is in education. These beliefs are far from set in stone but are hopefully the start of a discussion.
My Purposeful Practice Beliefs:
- Students should practice what they understand. Practice without understanding can change the goal of the practice from fluidity of skills to simply getting to the end of the page to make the teacher happy.
- Practice should focused on supporting individual student learning challenges and enhancing strengths.
- Practice should be focused on progress and monitored constantly. If a student is not progressing then the practice needs to change.
- Practice can be and should be messy…we need to see where errors are occurring so that we can help.
- When students make mistakes (and they will) teachers need to be there to help them by offering support, feedback and additional instruction. We should use practice to inform instruction.
- Practice should be sustained over time. It is not a one time thing. In order for practice to become permanent students will need to move the learning into their long-term memory
- Students should be given opportunities to put their practice into authentic “game like” situation as often as possible. It is through the game that students can discover the purpose for the skills, transfer them to new situations and make connections.
- Practice can be cooperative and noisy. Students can learn from each other.
Once upon a time, in a land not so far away there lived a girl named Jennifer. Jennifer was a student and on this particular day she was sitting in her desk carefully writing her name on the back of a piece of white paper. When her teacher said GO and not a second before (it was strictly forbidden to peek) she turned over her paper to reveal a page full of math basic facts. As quickly as possible, she began computing math facts and writing the answers on the paper. The whole class was silent, the only exception was the quite sounds of pencils frantically scratching and the odd moan. The gauntlet had been thrown down and the race was on to conquer the sheet and then celebrate your triumph in front of your friends. After two minutes the class was told to stop..turn the page over and put their pencils down. Some students smiled with victory as the teacher walked between the rows collecting the sheets. Some students hung their heads defeated, deflated and quite frankly exhausted from the effort. Jennifer lived in both groups some days she felt the sweet sensation of victory, some days the sheer agony of defeat. On this day the sheet, only half completed had declared it’s victory over her. The teacher would return the worksheet the next day with X’s and checks marks on it, along with the final score out of 50. Students who did well were told to keep up the good work. Those who didn’t were told to try harder next week when Mad Minute day came. On this particular day Jennifer asked her teacher if they had to have Mad Minutes day every week. She was given this short, simple answer…”It will help you learn your basic facts”.
Years later Jennifer was a teacher, with her own group of students sitting before her eagerly awaiting their signal to turn over the sheet of paper and begin. She had been given the most wonderful opportunity to teach students their basic math facts and was using the one tool she knew would ensure that students learned… The Mad Minute. After all, she had successfully learned her basic facts and had long since abandoned using her fingers and toes…well most of the time anyways. Some of her students experienced success, some struggled, some downright refused to start. Jennifer reflected on this fact with a colleague the next day. Why didn’t the kids get it?…she was doing all she could…she had even increased her Mad Minute time to twice a week…yet they refused to learn. Her colleague suggested sending the worksheets home for more practice. Maybe parents would have the time to help the students continue to learn those basic facts. After all they had now completed the unit on operations.
As I reflect on this story I feel sad, for that young girl who felt defeated, that young teacher who knew very little about teaching mathematics, and for all of those students. I was that girl and knew how defeated the Mad Minute made me feel…yet I created that same experience for my students. I simply knew no other way. A few years later I heard a speaker say something that really struck home to me… “When teachers align what they teach… with what students learn…and with what they assess… they honour the learners in their classrooms.
Mad Minutes, at least the way they had been modelled for me, were considered the one stop shop for teaching students to learn and assessing progress in basic facts. Knowing what I know now I understand that they are none of those things. They didn’t teach…they evaluated, they didn’t support learning…they evaluated, at best you could say they assessed and provided feedback for teacher planning and instructional decision-making (which they didn’t). At worst…they evaluated. They became an activity for survival of the fittest. The strong survived to basked in their success. The weak were defeated, crushed and left to feel like math failures. No one was honored. If you were one of those bright-eyed, trusting students in my classroom…I sincerely apologize. You deserved a teacher who would teach so that you could learn. A teacher who would assess and use those assessments for learning. A teacher who would not send home the very object of your frustration only to have you experience failure in a new environment. You deserved better! Knowing what I know now…I COULD do better. I now believe that:
- Teaching mathematics is about developing student competence AND confidence
- Teaching of basic facts should be done in a way that is strategic, and in attainable steps that can inspire confidence
- Practice should be purposeful and targeted
- Fluency is important and students should be given opportunities to develop fluency that is built on a foundation of conceptual knowledge
- Monitoring of Progress is key and should inform instructional decisions
- Assessments can be timed if necessary but students should be allowed to finish and only “compete” with themselves
- Students should be given opportunities to see patterns within operations and connections between addition/subtraction and multiplication/division
- Numbers are flexible and teaching/ learning about them should be as well
My next few posts will continue to develop my thinking on purposeful practice and procedural fluency in a way that I hope honors our learners and inspires success. As always your comments and feedback are always welcome.