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2022 April 30

Secret Walks: Climate Action Fair

On Saturday, 23 April 2022, my wife and I walked to the Seymour Center to see what the Climate Action Fair was like.  We decided to take a different route there than returning, taking advantage of what we had learned from the Long-Antonelli Loop.


Click for high-resolution map. We went down King to the end (red), then over to Swift down to the rail-trail, down Natural Bridges to Delaware, Delaware to the trailer park, and around the pond to the bridge (yellow), then over to UCSC’s coastal campus and to the Seymour Center parking lot (green) where the Fair was held. Our return route went on the paths through the coastal campus, crossing the tracks at Shaffer Road, Mission to Western Drive, then Grandview to Escalona to Anthony to Bay to King and home (blue). The whole walk was about 5.6 miles.

I got a few decent bird and flower photos on the walk:


These blossoms on a tree on King Street were unfamiliar to us. After searching with Google Lens (using this and another photo of the tree), I think is is either an ash or a pistachio tree.


There are plenty of lupines blooming around town, but I can’t tell the different species and cultivars apart.


I was trying to take a picture of the fortnight lily—the hoverfly was an unexpected bonus.


Now that the trees and shrubs have leafed out, we only get peeks at Antonelli Pond from Delaware Ave.


In the park by the pond in the trailer park, California poppies are blooming.


So are the water lilies in the pond.


We did not recognize this yellow flower, but Google Lens identified it as silverweed.


In the overflow from the pond down to the beach, we saw a dark-eyed junco bathing. I had a hard time photographing it, because it moved around a lot, dunking itself and shaking the water off.


Here is a view of the pocket beach from the Peter Sunzeri Memorial Bridge over the pond.


One of the mobile homes has these cheerful porpoises decorating the end wall.


From Horizon Drive, there is a very good view of Natural Bridges State Beach and the tidepools. The tide seemed unusually low to us.


I can’t resist taking pictures of these agave whenever I pass them.


The mast of the wrecked ship La Feliz is still on display on the edge of the cliff, but I don’t know much longer it will be there—it looks like a good storm could either break the mast or erode the cliff beneath it.


We saw this song sparrow, but could not identify what sort of sparrow it was until I got the zoomed-in pictures off my camera.


Here is another view of the song sparrow.


At the Climate Action Fair, the best table was for the Marine Mammal Center, who had some lovely casts of skulls of marine mammals (and a few real skulls, though not in this photo).


More of the cast skulls, plus a couple of real skulls in front—the white one with a crest is the skull of a male sea lion .

There looked like there were other interesting tables and activities at the Climate Action Fair, but the awful music was way too loud and unrelenting. I’m going deaf and I found the music uncomfortably loud—my wife could not stand to be closer than about a quarter mile from it. Going into the Seymour Center only made the noise worse. Talking to people at the tables was nearly impossible, so we just got arepas from the Pana food truck and went home. If I knew who was responsible for organizing the fair, and if I knew they were planning to do such a fair again, I would tell them to throw away the amplifiers—have acoustic music or no music, so that the other activities had a chance.


We were unable to identify this yellow flower—we think it is probably a California native planted as part of the restoration of the wetlands, but my photo was not distinctive enough to identify it.


This yellow flower seems to be a gumweed, though I’m not sure which one.


We consider our walks well-formed if we see an egret—and here was a great egret hunting in the grasslands that (in a normal rain year) would be wetlands.


The great egret was successful in its hunt—we think it caught a gopher, but at max zoom I could not hold the camera steady enough (even with the monopod) to get a clear photo of the prey.


We saw a Little Free Library in the middle of the Homeless Garden, but I only took a photo of it from the road—we did not wish to take books away from the homeless people that the library was clearly intended for.


This grand pink flower stalk is from a Bechorneria. (The leaves are green—those red leaves in front are a different plant.)


The bees really love the echium flowers. I think that this was a different echium than Pride of Madeira, but I could be wrong.


As we crossed Highway 1 at Western Drive, we saw a shaved-ice truck parked in the shade, but we did not stop to get anything, as we had the walk light to cross the other way.


The leucospermums are still blooming all over town.


We had not seen this Little Free Library before, but there was nothing in it that we fancied.


This weird blue and purple flower seems to be a Cerinthe major (also known as honey wort).

2022 April 16

ECG: 2-electrode vs. 3-electrode

Filed under: Circuits course — gasstationwithoutpumps @ 12:23
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In Lower PVC frequency, I said “I did not do direct comparisons of the 2-electrode and 3-electrode configurations—I’ll have to try that sometime soon.” So I did that earlier this week, recording resting ECGs first with a 3-electrode configuration (with the bias electrode on my sternum, halfway between the LA and RA electrodes) and then with a 2-electrode configuration (with the bias wire clipped to the RA electrode).  The 60 Hz noise was slightly higher with the 2-electrode configuration, but after filtering and signal averaging the two recordings were almost identical:


The waveforms after signal averaging were remarkably similar. The PVC burden was also similar (20.1% for the 3-electrode recording and 20.5% for the 2-electrode recording).


The pulse rate from looking at time between spikes worked well for the resting recordings, but the autocorrelation method failed completely, so I did not plot it. The rapid fluctuation in heart rate within a narrow range is real, not an artifact of the algorithm—the heart beats are not perfectly periodic, and the PVCs may be making them even less periodic. The 2-electrode recording probably started a little after 400 seconds—PteroDAQ only time stamps when the file was saved, not what the t=0s time was. I should probably fix PteroDAQ to change that, recording both.


I tried recording a session on the exercise bike also. The PVCs are mainly during resting at the beginning of the session and at the end of a recovery at the end of the session—the PVC burden was only 1.4%.


For the exercise recording, the noise really disrupted the spike-based pulse detection, but did not interfere as much with the autocorrelation-based pulse detection. My peak pulse rate was about 151.5 bpm, by the autocorrelation measure. I’m not sure whether the sudden changes in pulse rate at 100s (when I started pedaling) and around 556s (about 130s into the recovery time) are real or not—the noise in the recording makes it a little difficult to determine the “correct” pulse rate.

The noise during exercise was not 60Hz noise and seemed to vary with whether I was inhaling or exhaling, so I think that it was probably caused by EMG signals from the pectoral muscles or perhaps the diaphragm. The spike detector was clearly missing a lot of the spikes, but making it more sensitive would probably result in false triggering on the EMG noise. I’m wondering whether putting the electrodes on my back, over the scapulae, would reduce the EMG noise, but placing those electrodes and clipping to them would be difficult without an assistant.

The autocorrelation-based pulse detection seems more reliable when exercising, as my pulse is more periodic and has few PVCs, and the autocorrelation method is less susceptible to aperiodic noise.  The spike-based pulse detection seems more reliable when resting, when the pulse is not as periodic and PVCs disrupt the pattern.

I’m also wondering whether a more strenuous exercise session would raise my pulse rate, or whether I’m getting close to my maximum heart rate.  The standard formula for maximum heart rate by age suggests that this may be close to my maximum, but the exercise does not seem all that strenuous, and a couple of years ago I could routinely push to 170 bpm (though perhaps on a device that was an unreliable reporter—it was built into a treadmill at the gym).  So sometime in the next few weeks I’ll try using a higher power output and seeing where my heartbeat tops out.  I’ll probably need to increase the cadence, rather than the resistance, as I’ve been using about 70rpm and 28Nm to get about 205W.  Raising that to 80rpm or even 90rpm is probably easier than increasing the torque.

2022 April 14

Secret Walks: Wilder Ranch Coastal Loop again

Filed under: Uncategorized — gasstationwithoutpumps @ 22:15
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I posted before about my first time doing the Wilder Ranch Coastal Loop on March 25. On April 10, I did the loop again (in the opposite direction) with a group from the Monterey Bay Stanford Club.  I biked there and back, parking my bicycle on the fence next to the parking kiosk, as there do not seem to be any more planned places to park bicycles. I picked up a map of the park from the parking kiosk. The walk was a very slow and leisurely stroll, with frequent stops to look at the scenery.  The average age of the attendees was probably a bit older than me.


This is either Sand Plant Beach (as the state-park map labels it) or Little Strawberry Beach (as Google Maps labels it). There is a trail down to the beach on each side, to connect up to the Ohlone Bluff Trail, but we did not go down to the beach.


The next beach east is off-limits to people, because of the harbor seals hanging out there.


The seals look very comfortable when they are sleeping.


Another pair of seals. Is the one in back molting?


This seal looked very happy to be playing in the waves.


The biggest change from my previous visit was the presence of pups—here is one surrounded by adults.


It looks like some of the pups did not survive.


Here is another pup, playing in the water.


We did not see many birds on this walk, but I did get one shot of a gull wading.


Unlike my previous walk, most of the group walked down the somewhat steep and wet trail to Fern Grotto Beach. Here is the eponymous fern grotto.


The ferns hanging down from the rocks are quite impressive.


Another view of the ferns.


Looking out from the grotto, you can see droplets of water dripping off the ferns.


The whole thing looks like a Victorian garden feature.


The ocean side of Fern Grotto Beach has some nice rocks for the waves to break on.


Here are the seals again, seen from the ocean side with my zoom lens.


Without the zoom, it is rather difficult to make out the seals—the group of them are just a few dots extending the lines of the cliff to their right.


This beetle on the trail appears to be a Chrysolina bankii, based on a Google Lens search and looking at many pictures of the species.


Here is the walking group seen from the back.


Wilder Beach is closed to the public, but with my zoom lens, I could just see the canada geese in Wilder Creek from the Wilder Beach Overlook.


California poppies are still in bloom.


But many of the poppies have lost their petals and are showing red skirts around their seed pods.

After the walk, we gathered at the picnic tables between the chicken coop and the goat pasture and ate the lunches we had brought. The group seems like a nice enough group of people, and I would be willing to go walking with them again, though the level of exercise was rather minimal (I got far more exercise bicycling there and back). The visitor center was open, so I picked up a free map of Henry Cowell Redwoods state park while I was there.

Secret Walks: Significant Trees

Filed under: Uncategorized — gasstationwithoutpumps @ 14:16
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My wife and I did not do a walk in the Secret Walks series on April 2, and on April 3 we just walked to and from the Colligan Theater to see the new play Remains to be Seen.  The acting was good (though the parts had clearly been written for some of the specific actors), but the script was weak—the jokes were predictable and the attempts at deeper emotional appeal fell a bit flat.  The audience liked it (over half rose for a standing ovation), but that says more about the uncritical nature of Santa Cruz’s Sunday matinee audience than anything else.

On Saturday April 9, we decided to do a short walk, trying to use the city’s self-guided Downtwon Significant Tree Walk, which lists, gives photos of, and provides interesting information on 25 trees, but lacks a map or clear directions.


The route starts at City Hall, down Church, then up Cedar Street, and Mission Street to Mission Plaza (the red line). It is then supposed to go down Green Street (the orange line), but we got confused and went back down Mission, Center, and Chestnut, before we figured out that the trees we were missing might be on Green (the purple line). The route continues down Chestnut to Walnut, ending at Calvary Episcopal Church (the green line). I added a return to City Hall to this map, but in reality we started from home and went to Mission Hill Creamery for ice cream after the walk, before heading home. Click for higher-resolution map

The drawn route is about 1.42 miles, but our detour added about 0.25 miles to that. With the walk for ice cream and to and from home, the total distance was about 4.1 miles.


The Canary Island date palm (Phoenix canariensis) at City Hall has a rather curved base—probably because it was planted too close to the building.


The cockspur coral tree(Erythrina crista-galli) has gotten a lot bigger since the city put out the guide to downtown trees.


There was a house finch posing on the top of the cockspur coral, and I managed to get a decent shot of it.


The flowers of the cockspur coral are rather interesting shapes.


The bark of the floss silk tree (Ceiba speciosa) has nice spikes, though I think that the tree on the other wing of City Hall has nicer spikes than the one they picked out for their photos. This is from the tree they picked.


Here is the floss silk tree viewed from across the street in front of the Civic Auditorium.


The next tree on the list is a jacaranda, but it is not very impressive when not in bloom.


In front of the Civic Auditorium is a Japanese cryptomeria (Cryptomeria japonica).


They also called out this flowering cherry, though it was not in bloom.


Well, there were a few sad blossoms left on the tree.


Also in front of the Civic Auditorium is this fine owl nesting box, though I have no evidence that any birds have ever nested in it.


Next to the owl box was a cherry tree that still had exuberant blossoms, though it was not called out on the city’s list.


Here is the whole of the unlisted cherry tree.


The city listing had this angel’s trumpet (Brugmansia x candida) next, though it is unimpressive when not in bloom. There are a lot of angel’s trumpets around town, and this specimen is not one of the best.


Across the street by the Greek orthodox church is a lily of the valley tree (Crinodendron patagua).


The leaves of the lily of the valley tree look a bit like oak leaves.


In the CruzIO parking lot is a large Magnolia grandiflora. I’m not fond of these trees, as they drop stiff waxy leaves that clog drain grates, and I find the smell of the flowers slightly unpleasant. I prefer magnolias with softer leaves and a shorter blooming season (there are many magnolias of different types around town).

There is supposed to be a katsura tree on the walk between the magnolia and the gingkos, but we were unable to find it—we could not even figure out where it would have been from the photo in the city handout, as we could not identify the buildings either. Perhaps someone with a better memory of Santa Cruz downtown buildings or trees could help us out here.


The gingko trees on Cedar Street were just coming into leaf.


The black walnut in the parking lot had been slated for removal a decade or more ago, but pruning it way back and letting the crown regrow saved the tree.


The red oaks (Quercus rubra) in front of the parking garage provide some welcome shade at the entrance to the walkway.


The red-oak leaves make a nice contrast with the sky.


This orange flowering gum (Corymbia ficifolia) is a little hard to identify without the orange flowers.


The newly built condos clearly took away about a quarter of the tree canopy.


The seed pods of the orange flowering gum have some interesting color patterns.


On the top of the hill, in the Santa Cruz Mission state park, is a bunya-bunya (Araucaria bidwillii).


I used my zoom lens to get a more detailed view of the bunya-bunya leaves, without having to go around to the entrance to the state park.


The Chilean wine palm (Jubaea chiliensis) is also in the state park.


This date palm (Phoenix dactilifera) is in Mission Plaza park.


I’m not sure whether this linden (Tilia spp.) is dead or just hasn’t leafed out yet this spring.


Either way, the trunk has an interesting texture.


Also in Mission Plaza is this dawn redwood (Metaequoia glyptostroboides), which is not a California native, but which seems to do well here.


The copper beech (Fagus sylvatica ’Atropuncea’) on Cross Street was difficult for us to find.


The smooth bark and colored leaves are distinctive for the copper beech, and they make a nice display against the sky.


On the same property on Green Street as the copper beech is this deodar cedar (Cedrus deodara).


The deodar cedar needles in close-up.


This coast redwood (Sequoia sempervirens) on Union Street is the locally endemic redwood—they get a bit big for city trees.


This star/Norfolk Island pine (Araucaria heterophylla) is visible from Chestnut, but is really on Rincon by the apartment building there.


I like the way that this coast redwood is flowing over the sidewalk, so I photographed it, even though it isn’t called out on the city list.


These London plane trees (Platanus x hispanica (acerifolia)) are on Walnut Street. (Sorry—no walnut trees there, and no chestnuts on Chestnut Street either—in fact, most of the tree-named streets downtown don’t have the trees they are named after.) The plane trees in town are all rather sickly with anthracnose and powdery mildew, but they survive—we have a couple in our yard too, planted by the previous owners. Neither my wife nor I care much for them.


The last tree on the last was a douglas fir, but it was taken out a few years ago—that green lawn to the left of the church is where it used to be.

After the missing douglas fir, we went to Mission Hill Coffee and Creamery for ice cream. I ordered two scoops, but as I was handing my wife her cone, the top scoop rolled off my cone and landed on the sidewalk, so I ended up with only the fig-goat cheese ice cream, and not the green tea ice cream as well.


This wisteria across California Street from the high school is not part of the route, but it is a listed “heritage tree” by the city, and it is just coming to the end of its blooming season.

2022 April 8

Press release for my book

Filed under: Circuits course — gasstationwithoutpumps @ 22:29
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World Scientific Publishing has released a press release for my book at  That press release is lightly edited from one I wrote for them.

The press release does not point to the lower-cost PDF version at, but I can’t really expect World Scientific to advertise the cheaper option, even though they did allow me to continue selling it.  They have not given me permission to use their cover design


Blue cover

for my PDF sales, so I will continue to use my own design:


I’m not that fond of their all-caps typesetting anyway, and the generic “tech” background has nothing to do with the contents of the book—but if they think that generic tech backgrounds sell better, I’m willing to believe them, as they have much more experience selling books than I do.

The text for the two versions of the book should be identical, but they are resetting it (with smaller headings and some other formatting changes), so the pagination will be different.

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