Category Archives: tech

GMO tech makes the Impossible Burger possible

… or at least economically practical.

Earlier this week I noticed a retweet of this event in my twitter feed:

Coincidentally, someone else posted this video about the Impossible Burger (which I hadn’t heard of before this week)

I always find stories about science and food to be interesting, and this even had a connection to my alma mater: the founder of Impossible Foods is Pat Brown of Stanford’s Biochemistry Department.

Via Google, I found some interesting things about the Impossible Burger. The video talks about their general approach of using analytical methods to figure out what constitutes the constellation of perceptions that we get when eating a particular food. But what this post is about is the secret ingredient: heme. When we talk about red meat, a lot of what makes it red is the iron in heme. I first learned about heme in any real detail at Stanford when I took intro biochemistry as an undergrad (back then the undergrads could take the same course as first year med students). Heme is found in myoglobin and hemoglobin, the major oxygen carrying proteins in muscle and blood. Heme is responsible for the “smoke ring” in BBQ. Heme is also found other proteins, and based on this story, it appears that Impossible Foods first tried to get heme from spinach chloroplasts. But I’m guessing that the yield was too low to scale up production, so they looked at another source.

Leghemoglobin is a heme protein that is made for nitrogen fixation. The Impossible Burger contains soy leghemoglobin, but it’s not actually made from soybeans, because the leghemoglobin is found in the root nodules, which are not normally harvested. Digging up the roots to get the leghemoglobin would negate some of the environmental benefits claimed by Impossible Foods, but it also is probably as economically inviable as getting heme from spinach leaves, if not worse. So to get the leghemoglobin, they cloned the soy protein into Pichia pastoris, a yeast used in biotech for protein overexpression. Here’s how Impossible Foods describes their ingredients:

The Impossible Burger is made from simple ingredients found in nature, including wheat, coconut oil and potatoes. We add one more special ingredient, called “heme.” Heme contributes to the characteristic color and taste of meat, and it catalyzes all the other flavors when meat is cooked. Heme is exceptionally abundant in animal muscle — and it’s a basic building block of life in all organisms, including plants. We discovered how to take heme from plants and produce it using fermentation — similar to the method that’s been used to make Belgian beer for nearly a thousand years. Adding heme to the Impossible Burger makes it a carnivore’s delight.

This struck me as kind of odd. Is there something special about Belgian beer fermentation that makes it more similar to Pichia protein production than normal beer fermentation? Belgian beer fermentation historically uses more wild yeast than others, but as far as I can tell from my reading, Pichia is not a desirable species in any beer fermentation, and the inoculum is going to be a pure culture, not the stuff falling off the cobwebs from a Trappist monastery.

The news coverage of the Impossible Burger has been pretty clear about the source of the heme. For example:

  • NPR:

    By taking the soybean gene that encodes the heme protein and transferring it to yeast, the company has been able to produce vast quantities of the bloodlike compound. Each vat of frothy red liquid in the lab holds enough heme to make about 20,000 quarter-pound Impossible Burgers. “We have to be able to produce this on a gigantic scale,” says Brown.

  • NYT

    Thanks to the addition of heme, an iron-rich molecule contained in blood (which the company produces in bulk using fermented yeast), it is designed to look, smell, sizzle and taste like a beef burger.

But what I don’t see is in either article is the three letter acronym with a lot of baggage: GMO. It’s understandable, but kind of a shame, IMO. Impossible Foods got applied to the FDA for their GMO-based heme to be Generally Regarded as Safe. Most scientists I know would agree with that for most, if not all, extant GMO foods. But if golden rice and virus-resistant plants for poor farmers aren’t enough to sway GMO fearmongers, vegan burgers for first-world foodies are unlikely to do much.

Speaking of GM burgers, it’s been 10 years since Nature Biotechnology published a report of GM cattle where the PRNP gene was knocked out. Will we ever see CJD-free meat in the butcher’s section? That one really is a previously impossible product made possible by GM technology.

Sous Vide circulator setups

The last post about making lemon curd shows my two immersion circulators, an original, no-longer available at US voltage, Classic Nomiku and an Anova Precision Cooker (bluetooth only). I’ve had the Nomiku a since Thanksgiving 2013, while I got the Anova about a year later as part of their Kickstarter release (I went in with a colleague on the discount for 2 deal).

Since then the market for circulators has moved on. With two units that are both doing fine (knock wood), I’m not in that market for us these days, but I like to see what’s new. Even though I’m not looking for myself, these are nice potential gifts. has a recently updated roundup of several of the units that are currently available. The newer wifi version of the Anova (their pick) continues to be one of the most popular, but the model that seems to be very trendy right now is the ChefSteps Joule (which I have not seen in person yet). If I was shopping for a new setup or looking to give one as a present, I think I would seriously look at the Joule.

Kenji Alt-Lopez at Serious Eats reviewed the Joule in October, and came up with a conclusion that is similar to what I’m hearing elsewhere. The Joule is awesome except… It’s smaller and more powerful than the Anova, is waterproof, and has a cool magnetic base in addition to a clip. If I had a Joule and was looking to use it in a nonmagnetic container, I’d probably just put something like our enameled cast iron heat diffuser in the bottom.

The “except” is that part of what allows it to be awesome is that it can only be controlled via wifi or bluetooth. This means an iOS or Android phone or tablet via an app, or an Amazon Alexa (Echo or Dot) voice recognition system.

This is a view of my two circulators in my 12 quart Cambro box. Neither touches bottom and the Anova rides higher.

The Joule has a lower minimum water depth than other circulators at 1.5″.  By contrast, it’s 2.5″ on the Anova and 3.5″ on my Nomiku classic.  The new Nomiku wifi is also 1.5″. But that number is more meaningful with the Joule, because it can actually sit on the bottom of the container, while the others are really the distance from the bottom of the circulator to the minimum line.

Why would you want to use less water? The obvious reason would be if you’re in a drought area like California, and it seems silly to heat 6 quarts of water to cook a couple of sous vide eggs. But it’s also sometimes nice to be able to have a precisely controlled double boiler, and for that application it helps if the mixing bowl you’re using can actually sit on the bottom so it doesn’t float or capsize. I’ve also done sous vide cooking in Mason jars that are not fully submerged.

The photo above point out a couple of interesting differences between my Anova and my Nomiku. One of the things people didn’t like about the Nom is the external power brick. It’s one of my least favorite parts about it too. But what you can see from the photo part of why the Anova and Nom aren’t waterproof: there are cooling vents on both of them. On the Nom they’re on the power brick, but on the Anova they’re right above the clamp and on the top.

I find myself wondering if some of the complaints about failing units from Anova are related to users getting water in those vents. I’d also note that since the Anova is available on Amazon and is the most popular circulator, it’s going to have more complaints just by mass action.

The setup you use can affect minor issues with how you use your circulator. I like to put my setup next to the sink to simplify filling the box and dumping the water afterward. In our kitchen the distance from the countertop is about 17″, which is a bit less than the current standard of 18″. From what I can tell from looking at various websites, there is a lot of variation from this distance, especially in older kitchens. There’s an under-counter light fixture to the left of the sink that makes the clearance even shorter. The extra bit of space when mounting in the 12 quart Cambro means that the top of the cooker runs into the light fixture. This will be worse with any pot taller than the 8.25″ height of the Cambro. Depending on your countertop material, it’s recommended to put a trivet under the container, so that will add some additional height. The Joule is much smaller than the other circulators out there.

Sweethome loves the clamp on the Anova, because it allows you to do things like this. The Nomiku is too long to clamp to most of our pots, except for the larger stock pots. But I find that the Anova’s screw based clamp makes it harder to move between containers, and to detach when filling or dumping water. I find that I leave the clamp attached and remove the Anova body instead of unclamping the whole thing.



Although I’d seriously consider the Joule if I was just starting with Sous Vide, I’m still very happy with my two circulators. Because the Cambro is my main container, I’m going to keep using the Nomiku as my main machine even though it does have some drawbacks compared to the Anova, such as humming when not running (I can leave the Anova plugged in, but the Nomiku is kind of annoying in standby mode due to the hum; I just unplug it). In addition to the clearance advantage, the Nomiku is a bit more powerful.

Last night I finally got around to stealing an idea from this hack to make the external power brick less annoying. A $3 package of adhesive backed Velcro had 2X what I needed to give the brick a removable mounting point on the Cambro. I also got a folding silicon trivet that matches the Nomiku’s color scheme.


Linksys router speed problem solved

I was mystified at the painfully slow wifi I was getting at my mother’s house. She lives in Silicon Valley where decent speeds should be expected, but I was getting <1 kbps download on Weirder, the upload speed was 5-6 kbps. Via Google, this blog post explained the problem and solution, which is worse on Apple products. Changing one config setting increased the download more than 25x on my ipad.

RoomScan Pro

Today we went to a seminar about remodeling with Stearns design-build to get some ideas about some remodeling plans. In talking about things, I decided that we really need a better diagram of our house layout. It doesn’t have to be super precise, but I want a starting point to sketch from. I thought there might be an app for doing measurements and it turns out there are a couple

  • Magicplan uses the camera. It sounds interesting but this review makes me leery of the “subscription” part. It also seemed to me that there could be issues with obstructions.
  • RoomScan from locometric works using the GPS, gyroscope, the camera and who knows what else (accelerometer?) to take measurements based on tapping your phone against the walls

As with anything that involves extrapolation from the phone to do a complex task, getting dimensions right with RoomScan isn’t quite as easy as it looks in their demo video. But it’s still pretty cool, and their support people are very fast to answer questions via twitter to @locometric.

Testing – technique matters


Figure 1

In my first attempt to create a floor plan (Figure 1), the numbers were off. The app did warn me about the measurements possibly being off. RoomScan does provide a way to adjust the lengths of walls manually, but some of these were way off. Could this be due to the extended wifi network? Are the numbers reproducible? Was I doing it wrong?

RoomRoomScan L (EW)RoomScan W (NS)L W
Master BR11.511.513.7514
Master Bath10.5 in 2 segments119'1"7.5
Main Hall263303.5

I decided to do some experiments. First, I repeated the hallway a couple of times. After two failures, I switched the phone to Airplane mode. I also changed the tapping pattern (see below). RoomScan worked fine in Airplane mode, showing that the wifi and cellular signals aren’t being used. Once I got it right, I switched Airplane mode off, and did more replicate scans. Figure 2 shows the last test.

Test 1Failed
Test 2Failed
Test 3313.5
missed a door
Test 430.5
21 to BR door
Test 530.5
21 to BR door
Figure 2

Figure 2

So, I think that the problem with dimensions is that I wasn’t moving fast enough for the accelerometer to work optimally. RoomScan warns you about this. There’s a voice message that says things like “I work best if you move quickly but smoothly” or “Keep the time between taps short” (not transcribing these exactly”. It appears that RoomScan uses the lack of light from the camera to determine that you’ve tapped a wall.

It also took me a couple of tries to figure out what it wants to close the polygon. It’s not enough to tap on the same wall past the starting tap. For these, I started on the lower wall to the left of the BR door and went counterclockwise. At the opening I did wall tap, opening tap, opening tap on the opposite wall, wall tap before heading down the long part of the hallway. Coming back, I had to go through through that whole sequence a second time to close the loop.

Adding rooms

Next, I deleted all the hallway tests but the last one, which I used as the hall. Unfortunately RoomScan wouldn’t let me rename it. I got the Pro version because it wasn’t very expensive ($4.99) and it allows you to add rooms through doors. You open a previously scanned room and touch a door or opening as a starting point. RoomScan brings up a control wheel with different options. These include the ability to change the kind doors to openings and vice versa, and flip which way the doors open and which side the hinges are on. Tapping a wall gives a similar control wheel that allows you to add doors that you didn’t scan in earlier.

RoomScan control wheel

Figure 3. Control wheels for editing adding rooms

Selecting add room through door/opening prompts you to name a new room and then click Add. Depending on what kind of connection you start at, it tells you to start in the middle of a closed door, or on one side of an opening.

In my initial tests, I didn’t get the opening at the end of our hallway right, so I used the add door function to create an opening.  Starting with an opening you’ve added via the edit function doesn’t work right. I’ve emailed service@locometric with screenshots, and they replied very quickly (on a Saturday no less) promising a bug fix in the near future regarding the openings behavior. But the add room through opening works fine if you create the opening in the original scan.

Figure 4

Figure 4. tapping to get an opening.

Figure 4 is an image RoomScan support sent me to show how to do it right. Essentially, you double-tap each side the opening: once to set a wall point and the second time to set an opening point. The order goes wall-opening-opening-wall.

Once my scanning technique got better, I was able to add several rooms off the Test 5 hallway. Figure 5 is what I have so far. RoomScan automatically places each room based on the opening or door you previously started with. You can adjust this by tapping a room in the overall overview and dragging it to a new position. My three problems with this are

  • It isn’t precise enough. It would be really nice to be able to just nudge a room by a little bit. You can see the nudge problems in how the rooms line up.
  • Roomscan’s floor plan view tries to merge openings and doors into nearby spaces a little too aggressively.
  • It tends to crash in this mode

I want the connection with the opening I started with, and there are times when the openings do need to be connected. For example, our dining room has openings into both the living room that should be connected when I scanned the Dining Room starting from the Kitchen with the Living Room already on the floor plan. This connection is presumably made by recognizing that two openings from adjacent rooms are overlapping. But the overview also tried to fuse two kitchen closets into the back of the Master Bathroom. It didn’t create new doors in the bathroom, fortunately, but it was disturbing to watch the doors connect like cytoplasmic bridges between cells as I tried to move the Kitchen into place.

I also had to do some fudging on where I think the boundaries of the rooms are. The way our flooring is set up, I think of the boundary between the living room and Kitchen as being diagonal. I don’t think RoomScan likes diagonals. I’d be interested to see how it works on floor plans with different angles between the rooms.


Figure 6. The partial floor plan


RoomScan Pro is not going to replace a professional draftsman spending days and $$ to generate new architectural plans for your house. It’s not going to give you elevations. But at $4.99 it’s a lot better than what we were doing for early stage brainstorming – running around with a too short tape measure and sketching on paper. That said, what I think I’ll end up doing is:

  • Tweak the measurements in the app and export the image
  • Import the image into Notability or a drawing app and sketch on top of it on my iPad.

That’s partly because I’m not sure how to export RoomScan output as objects to a drawing program where they can be edited on my laptop (It’s not clear that any of the home/interior design apps handle that well either; what are the file format standards, anyway). It’s also because even if I could export editable files, I don’t currently have anything to import and edit them.


Adventures with the iPhone music app

My wife and I like to joke that stores do their market research by figuring out what we like a lot and then discontinuing those items. That’s how I feel about Apple’s decision a couple of iOS upgrades ago to decouple Podcasts and iTunes U from Music.

I like to listen to podcasts. I listen to podcasts much more often than I listen to actual music. I often listen to podcasts using my iPhone hooked to the USB connector in my Honda Civic hybrid. Before Apple separated the apps, my phone would play the next podcast when it finished the episode I was listening to. Because I have a very short commute, I usually have a bunch of episodes to catch up on.

After the apps were separated, my phone tended to default to the music app instead of continuing to play podcasts. This was annoying but I tried to avoid the safety hazard of fumbling with my phone while driving (at least until a stoplight). It wasn’t so bad… the song that came up was usually Miles Davis’ All Blues, one of the greatest jazz standards of all time.

But that was before the most recent iOS update, which seemed to have turned on some kind of cloud sync with my iTunes account, even though I had it set to “Sync selected playlists, artists, albums and genres”. A couple of years ago I downloaded the free Apple Christmas music compendium, which included the incredibly insipid and annoying Above the Northern Lights by Mannheim Steamroller… and until just now I couldn’t delete it.

  • I deleted it from my laptop and resynced. It was still there
  • I swiped left and got the delete button on my phone. I hit delete. It came back
  • I tried the above with many different permutations of settings on the phone and the iTunes app on my laptop. It was still there.

Many of these attempts were based on Finally, I found this thread on the Apple forums. The solution involves deleting all of your music and then resyncing with a computer.

  • On the phone:
    • Settings > Music: make sure Show All Music is Off
    • Settings > General > Usage > Music: use the edit button to delete all the data from the music app
  • Connect to the computer and resync to copy music from iTunes to the phone

Note that this doesn’t work in the untethered world that Apple aspires to for iOS devices. Also, when I turn Show All Music back on, the damned song comes back. I never subscribed to iTunes match, btw.

As an Apple stockholder, I usually just let my proxy default to the current directors. But I would consider voting for an alternative board whose platform was to fire whoever at Apple is responsible for splitting podcasts out of Music (deleting the annoying song was not a priority for me until the stupid cloud song became the default) and whoever made it so freaking hard to delete songs.

Open source communities are different

Via Althouse, Farhad Manjoo argues in the NYT that Brendan Eich had to resign because:

Mozilla is not a normal company. It is an activist organization. Mozilla’s primary mission isn’t to make money but to spread open-source code across the globe in the eventual hope of promoting “the development of the Internet as a public resource.”

As such, Mozilla operates according to a different calculus from most of the rest of corporate America.

Like all software companies, Mozilla competes in two markets. First, obviously, it wants people to use its products instead of its rivals’ stuff. But its second market is arguably more challenging — the tight labor pool of engineers, designers, and other tech workers who make software.

When you consider the importance of that market, Mr. Eich’s position on gay marriage wasn’t some outré personal stance unrelated to his job; it was a potentially hazardous bit of negative branding in the labor pool, one that was making life difficult for current employees and plausibly reducing Mozilla’s draw to prospective workers.

A commenter or Manjoo’s piece adds:

I wonder why this man was given this position in the first place if his views are so counter cultural at Mozilla. Or, if the views were unknown, what does that say about management of the company?

A reply points out that Brendan Eich, as a cofounder of Mozilla, might be in a better position to be familiar with the culture of Mozilla than Eleanor from Augusta Maine. There’s a basic problem with this argument: it presumes that the labor pool is contains more talented people who object to Mr. Eich’s private political activity than talented people who now will avoid working for Mozilla due to concerns about working for a project where outside activities are a litmus test. The idea that programmers and engineers are homogeneously enlightened progressives is… let’s just say counterintuitive. Eich is himself the counterexample to political homogeneity of talent. He’s not a John Scully from Pepsi going to Apple. The man invented Javascript, which runs a large fraction of the current web.

In my view Manjoo and Mozilla’s management have it exactly backwards. Depending on a community makes it even more important to defend the right of people you disagree with on extracurricular matters to participate. Importantly to this question, as far as I can tell, there have been no reports that Eich’s political beliefs manifested as creating a hostile work environment beyond those who are sensitive to the existence of those beliefs per se. It’s not like I’m seeing reports that Eich did anything like the infamous Larry Summers talk about women in science (I find this story interesting in part because of parallel issues in academia and science).

Imagine a boot stamping on your ideas forever

Via Daring Fireball, author Charlie Stross writes about his hatred of Microsoft word.  I don’t know enough to evaluate the technical arguments about design and file formats, including the comments left by a commenter “globetrotter” who self-identifies as a MS program manager for early versions of Word. But the empirical experience of Word is sufficient to share Stross’ loathing for it, shared by the majority of his commenters.  I just about choked when I read globetrotter’s comment:

In Word you can open a 200,000 page document, and make 20 quick edits and save without it taking most of the afternoon.

Really? Now it may be true that Word can handle a 200K page plain text document better than competitors.  But if this 200K page document contains any embedded textboxes, figures, or tables that are the reason to use Word vs a plain text editor, it’s likely to crash horribly.  I’ve suspected for years that Word has a calendar function that crashes more frequently as grant deadlines approach.

Even when it doesn’t crash, I hate the way Word (and Office) change your text to “correct” it. Word and Powerpoint are responsible for a generation of biologists misusing the abbreviated forms of the binomial species names; I’ve lost count of the times I’ve seen E. coli rendered as E. Coli. And things like this comment are all too familiar:

 One of the things the Tech Ed supplied us was a monthly Q&A column. Going over his copy, I noticed that he’d eschewed the usual “Q” and “A” prefixes in favour of “Q” and “R”. “Question and Response, I guess… OK, bit quirky, bit individual, leave it in”. The second question and answer were also given as a pair of paragraphs beginning “Q” and “R”; the third question and answer, however, came as a pair of paragraphs beginning “S” and “T”.

At this point I saw what was going on, and changed the “R” prefix to an “A”.Word changed it back, right before my eyes. It happened several times before I got the changes to stick, even after I’d told it not to format the paragraphs as numbered lists.

Editing a multiple choice test in Word can be a real adventure.  Then there are things like mysteriously unselectable formatting elements, and unusably dense track changes markup.

So I hate Word too.  So why do we use it?  First some minor quibbles:

Was Word first?

Stross writes:

Steve Jobs approached Bill Gates to write applications for the new Macintosh system in 1984, and Bill agreed. One of his first jobs was to organize the first true WYSIWYG word processor for a personal computer — Microsoft Word for Macintosh.

Xerox Bravo was first, but the Alto never made it to the market. Similarly, the WYSIWYG in the Xerox Star and Apple Lisa could arguably be discounted. But if we use the original Mac as the personal computer where WYSIWYG Word first appeared, both MacWrite and WriteNow (originally for the NeXT) were available before the first version of Word for the Mac. I wrote my PhD dissertation in WriteNow before Word was available. Perhaps Stross is saying Microsoft promised the first WYSIWYG for a personal computer, but was late to deliver it.

TeX and scientific writing


Not all commenters agree, but you see this kind of thing in discussions of Word suckitude

I know that for scientific publications, latex is the rule (a friend of mine does a lot of mathematic translations).

LaTex is the rule in some fields, but not others. NSF’s survey of doctoral scientists from 2008 (pdf) shows that 164,000/651,200 employed PhD scientists and engineers were in the life sciences.  Biologists use Word. The NIH grant templates are in word. Our journals accept Word files. Our journals even link to downloadable Word files as supplemental data (ugh).  But if my Facebook friends around grant time are representative, there are plenty of other biologists who hate Word.

If we hate it, why do we use Word?

To some extent, it’s for the same reason everyone else does: because everyone else does. The ability to edit Word documents is assumed when you are collaborating with others.  Collaboration with people who didn’t want to use Google Docs is why I did my most recent upgrade to Word; there were docx files that my older version could no longer convert. If you’re not collaborating with others who demand the ability to work in Word, the journals and granting agencies take pdfs these days, so you can switch to anything that can generate pdfs. Not that long ago, journals and granting agencies expected hardcopy, so you could do your word processing in anything that could print.  Several colleagues and I clung to WriteNow  for a long time.

For biologists like me, I think grants drove people to use Word more than publications.  After all, for publications, we still submit things in dull double-spaced text without inline figures and tables. The publisher has the fancy stuff to do the layout. But for the grants we used to print and now submit as pdfs, there is no other publisher/design house to handle the layout. And as much as we as scientists may try to value substance over style, all other things being equal, a grant that is easier on the eyes gets the edge.  Inline figures and tables for a grant are even more important now that page limits have been reduced at NIH. And even if a campus had their own service to do layout on our grants, we probably wouldn’t use it because it wouldn’t let us use every last available procrastinated minute before the application had to be sent.

But we can make inline figures and tables with a variety of software packages we hate much less than Word.  As a Mac user, why don’t I use Pages, for example? Some of it is the collaboration issue described above. But the other is summarized in one word:


Scholarly writing means citing sources and at least in my part of the life sciences, EndNote is the de facto standard, and uses academic discounts similar to those Microsoft uses to keep people from switching.  There are alternatives to EndNote, but as far as I can tell, plugins to support EndNote-style Cite while you write functionality are relatively new. The expectation that collaborators will be able to share EndNote libraries reinforces the  disincentives to change.

Could Word lose its dominance in science writing?

Of course. I’m old enough to remember paying typists to do manuscripts and grants. That’s not coming back, but it means I also lived through the days when people advocated training all students to use WordStar, and I remember the competitive market for plastic sheets that sat over your keyboard with the Wordstar key bindings.  Perhaps WordStar’s dominance then was not as great as Word’s is now, but there is space for competitors, based on limitations of Word. I already use a combination of Google Docs and Word, where Word is used to tweak the final version, put in references, and so on.  Reference managers that work with Google Docs are starting to show up.  As I write this, Apple is preparing an announcement about iWork on iCloud.

Firefox 23 mixed content blocking and Galaxy

The Galaxy genomics workbench has problems with mixed content blocking in Firefox 23 when it’s running under https, which it should be based on sending logins and passwords. When you click on any of the public data sources (e.g. UCSC Tables) under Get Data, Firefox blocks it.  The solution is to turn off mixed content blocking, as described here.

Unfortunately, this is a global configuration rather than per domain.



Microfiber stylii

Most of the time, I use my finger on my iPad, just as Steve Jobs intended. But there are times when a stylus is nice:

  • Taking handwritten notes
  • Actual drawing

For a while, I’ve had a Wacom Bamboo stylus, which is one of the better ones that have soft rubber tips.  But recently I got a Boxwave Evertouch, which is one of many relatively recent offerings using microfiber tips instead of rubber. This makes the stylus slide much more smoothly than even the Wacom, and so far I like it.  It also helps that the Boxwave is much cheaper.