Responding to the Water Droplet Challenge

Editor,

I'd like to submit an answer to the water droplet challenge (Kevin Kilty, "A Droplet Puzzle," The Citizen Scientist, 04 January 2008).

I think there was a layer of fine droplets on the varnished table, similar to the fog that appears on mirrors when you breathe on them.

When the two water drops fell on the table shown in the picture of Kevin's table, in each case the impact caused them to spread out and "swallow up" the microscopic droplets into a large single pancake of
water.

Very quickly, the water must have retracted back into a bead, since varnish repels water, leaving only the cohesive attraction of the water to act on the pancake shape. The radial symmetry of the pancake shape most likely caused the water bead to form at the center of the impact zone.

I would never have guessed such a thing could happen had I not read about it. Since you talked about digital cameras, it might be interesting to view a high-speed movie of such an impact the way milk drops were popularly filmed some 20 years ago.

Mark Valentine

Books About Microscopes?

Editor,

would you know of a place where I can read about good books on microscopy?

I found a couple of old ones worth reading and having. But it seems that lately this science is going away.

Richard LeBlanc

This is an important question, so I posted it on the SAS Community Forum. Astronomer and microscopist Bill Dembowski posted a reply that's well worth reading:

Most of the books I have on the subject are primarily guide books to the identification of microorganisms. As for those dealing with microscopy itself, the techniques of specimen preparation and use of the instrument, only two are worth mentioning.

“The Microscope and how to use it” by Georg Stehli is a decent introductory book but rather outdated (1955). It does have the advantage of still being in print and under $10 new.

By far the best book I own on general microscopy is “Exploring with the Microscope” by Werner Nachtigall. It is only 160 pages but beautifully done, both the text and illustrations. You will have to check the used book market where prices are now ranging between $50-$150 (ouch). I bought mine new less than 10 years ago and the price on the dust jacket is $19.95 (hardback).

Most of the others that I either have or have seen are tailored to grade-schoolers or university level students that have access to really advanced equipment.

Bill Dembowski

Digital Photography Question

Editor,

Regarding the article in the December 2007 issue of The Citizen Scientist about digicams being an essential tool for the amateur naturalist, what are examples of things we can take pictures of to help contribute to science?

I know astrophotography helps a lot, but what about those of us who don't know (at least not yet) how to do astrophotography?

Cristina Montes

Cristina, please see some of the previous articles on this topic in TCS (use the search box). For example, you might want to look at past installments of "Gallery". See anything by Bill Dembowski. See the great photos by Bill Hilton in his "Hilton Pond" series. See also "The Citizen Scientist's Most Versatile Instrument" and "How to Analyze Digital Images." Editor.

Clarifying the Vacuum Tube Era

Editor,

The article in the 4 January 2008 issue of The Citizen Scientist was quite interesting ["The Vacuum Tube is a Century Old" by Forrest M. Mims III]. However, there are a couple of points which need
clarification. Vacuum tubes are still in common use, although in some what more specialized applications than in previous decades. For example, while LCDs and plasma screens have mostly replaced CRT monitors, there are quite a few CRTs still being made, sold, and used (and, a CRT is nothing more than a large vacuum tube). Additionally, quite a few television transmitters (and even some radio transmitters) still use vacuum tubes, which excel at producing large amounts of RF power at high frequencies (e.g., Some UHF TV transmitters produce 50KW of power at UHF frequencies, usually via a Klystron vacuum tube.). Additionally, microwave ovens are based on Magnetron vacuum tubes.

As for vacuum tube technology peaking in the 1940s, I'm more inclined to believe that the technology peaked in the 1960s (or, perhaps the 1970s). While transistors were making inroads to applications traditionally occupied by vacuum tubes, there were still a huge amount of vacuum tubes being produced. Plus, vacuum tube technology was still advancing, even as late as the 1960s, with improvements in cathode coatings, multi-sectioned vacuum tubes (e.g., "compactrons"), and size (e.g., subminiature vacuum tubes).

David W. Glass

David, I should have stressed that the article emphasized the consumer and computer uses of vacuum tubes vs. transistors/ICs. As for the peak of vacuum tube technology, it would be interesting to see a sales chart. I suspect that far more tubes were sold in the 1950s than in the 1970s. Editor.

Clever Idea for an RFID Module

Editor,

I recently discovered that Radio Shack now carries at least four new modules: 1.) MEMS accelerometer; 2.) acoustical range finder; 3.) light- to-frequency module; 4.) and an RFID reader with tags included in the same package. All but the last have obvious applications in robotics. For that last module I suggest "Wallet Watcher for Washers." This would be a washing machine with an RFID attached to it. Anything you wouldn't want to get washed (such as a wallet) would have an RFID tag in it that would sound an alarm on the washing machine when you are about to throw it in. One of the few projects that could instantly pay for itself :)

It seems like modules are becoming quite popular, and it's great to see Radio Shack providing hobbyists and experimenters with updated capabilities.

Mark Valentine

Cheers for Nuts and Volts and Science Probe!

Editor,

What a delight when I read your feedback and good comments about Nuts and Volts magazine. I'm a real supporter of your work that goes back to the very first days of Science Probe! I still have them all and had them bound into a nice hard cover book.

I found especially interesting the synergy comments you had on Nuts and Volts editorial content. I've just resubscribed to them for the next three years after a short break of few months where I purchased some of them from the bookstore.

When I look at my huge library and at how many different technology magazine came and went, especially electronics magazines, I'm a bit concerned.

To my knowledge, only Nuts and Volts and Circuit Cellar are still active.

I've added the The Citizen Scientist to my best bookmarks and will read regularly.

Richard Leblanc

Welcome aboard, Richard. The Citizen Scientist was inspired by Science Probe!, so I'm glad to know you still have your old copies. As for Nuts and Volts, it's the best. Editor.

Home Built Scientific Instruments Web Sites?

Editor,

How about a collection, if such is available, of web sites with instruction on building scientific instruments? Or a collection of book titles or magazine articles of same.

Byron Hodges

Thanks for the suggestions. Ralph Coppola has uncovered and publicized hundreds of such sites in his "Wanderings" column, which resumes in this installment of The Citizen Scientist. You can find back installments of his columns on the TCS section of the SAS web site. Projects are of very high interest to readers of The Citizen Scientist, and we're always looking for good ones to publish. Editor.

Oxygen Deficiency in a Marine Bay

Editor,

We have here a marine bay where oxygen is deficient and fish die. The experts find large plankton that grow in hot weather and die, consuming oxygen in the process. But the experts may fail to consider shoreline homes without sewers or septic tanks that discharge waste into the saltwater, including laundry bleach and bleach powders. These materials kill delicate photosynthetic plankton. Fish death may be caused by the scarcity of native plankton, and summer blooms are caused by unused nutrients.

Glen Hemerick

More About Heat and Cold

Editor,

I was delighted to see Jeffrey Bledsoe's letter about Dry Heat & Cold. In 1953 I had a scholarship grant from the Institution of Mechanical Engineers in England to spend a year in Milwaukee doing R&D on off-highway equipment. Having grown up in that damp place with only one fire in a house and in a factory where the warmest place was the tool room at a hoped for 68º F. Taking notes at college with gloves on. I had an uncomfortable time adjusting to Milwaukee's indoor temperatures. During that first winter I walked everywhere, usually with my coat open and was not at all uncomfortable until one Sunday morning in bright sunshine and crisp squeaky snow I got a fright when I found my nose would not wriggle.

Colleagues pulled my leg relentlessly. As a result I started to take note of temperatures and spent some time reading the ASRAE handbook on human comfort. (In England you were either comfortable, too hot, chilly or perishing.) On arrival back in the UK I placed thermometers all over the place and discovered that sometimes with the temp in the mid 40'sº F I was more miserably cold than I ever felt in Milwaukee's winter. Hence it helped motivate me to emigrate to Canada.

In the 50+ years since I often feel quite upset at the weather forecasters who like to quote big numbers of wind chill effects and humidity indexes. While they may be based on ASHRAE's tables, they do not reflect human comfort in the real world. I suspect they are based on wind tunnel experiments. I will look forward with interest for a useful explanation of this element of human comfort.
(Ask any GI's who spent time in the UK during WW2 how they survived a winter there.)

Ivor Mansell

Mud Daubers and Black Widow Spiders

Editor,

I'm hoping that mud dauber wasps occur in or around Albuquerque, New Mexico.

Why? I'm writing a novel that includes the use of wasps for their predation of certain
venomous spiders. This is at the core of several dove-tailed
sequences of garden-related memories of my vieja of means, Nevada
Fernandez-Hernandez. Problem is, I only remember seeing paper wasp
nests in Albuquerque (in my parents backyard). . . .

Because as a child I shivered in fear at the mention of black widow spiders, I was happy to find that mud-dauber wasps prey on them! (I don't see how the wasps, or their larvae, can gain
any nutrition from a gram of pure black-tar evil, red hourglass tattoo, hairy legs, etc.,but what do I know?). . .

Do mud-dauber wasps live and work in the greater Albuquerque metropolitan area? If this is not
in your area of expertise, please forgive the intrusion, and I thank you in advance for your consideration.

J. Ambrose Lucero

I do not recall seeing mud daubers in Albuquerque, where I lived from 1968 to 1975. But I suspect they might be found there. After all, adobe is the traditional building material in New Mexico. I suggest that you do a Google search. As for black widows and mud daubers, please see my article and photo on this here. Mud daubers are quite good at capturing black widows, as you note. Editor.

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