Author Archives: gmcdavid

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About gmcdavid

Retired IT professional with a wide range of interests. Married. Three sons, two with autistic-spectrum disorders and the third being transgender with Ehlers-Danlos syndrome. From Chicago but now living in the Twin Cities metro, Minnesota. Episcopalian. Carleton College (BA 1972, physics) and Stanford University (MS 1974, Applied Physics; MS 1976 Statistics).

Electrons and Positrons

I have known about Electron–positron annihilation for at least 52 years, from my course in Atomic and Nuclear Physics at Carleton College in the spring of 1970 if not before. The reaction is

e + e+ → γ + γ

I had always assumed that the inverse reaction

γ + γ → e + e+

was also possible because of time reversal symmetry. Apparently so had everyone else, but it has only recently been observed: Matter arises from light? We finally know the answer to this question!. Even now there is a caveat about “virtual” as opposed to “real” photons.

Slackware Diary – 2

Continuing from Slackware Diary – 1

Fixed the prompt by copying .bashrc and .profile (renamed as .bash_profile) from my primary Ubuntu system. This works and I have nice color prompts in Slackware. Need to see if I have scripts from my previous Slackware days to add environment variables, aliases, etc. Life in Slackware means a lot of time on the command line.

The next task on my list was to install Flatpak so I could use apps from Flathub

“Failure is always an option.”-Adam Savage

Rang Gaeilge, 20ú lá mí Aibreáin 2022

Duinnín agus Imleacán Kali (tuilleadh)

Dineen and the navel of Kali (continued)
  • ‘Rugadh agus tógadh Marie i Sr. Cuffe agus is ansin atá cónaí ormsa. Baisteadh Marie i Sráid na mBráithre Bána. Dhein sí a céad chomaoineach ann. Tá ag éirí go maith le Mr. McCausland sa bhanc agus thóg se an teach seo ar cíos anuraidh. Ar ndóigh, ní bheinnse ag seadú anseo ach go bhfuil gá ag Marie le cúnamh agus Mr. McCausland san … ospidéal.’

    ‘Marie was born and raised in Cuffe Street and that is where I live. Marie was baptized in Whitefriars Street. She made her first communion there. Mr. McCausland is doing well in the bank and he rented this house last year. Of course, I wouldn’t be here except that Marie needs help and Mr. McCausland is in the … hospital.’

    comaoineach Communion f
    cíos rent m
    seadú Settlement; stay, wait m
    cúnamh help m

    Léigh tuilleadh

  • Installing Slackware 15.0

    Back in February I looked at the Slackware Linux web site. After years of working with Ubuntu, and occasionally its parent Debian, I decided to see if I could install Slackware and get it to work. I used it a lot in the first years of the current century. Could I still manage it now, or had the comforts of the Ubuntu installation process dulled my edge? From Slackware 15 – The old brigade:

    Slackware is deployed using an ncurses interface, with a set of menus where you must make intelligent choices, including partitioning and package selection. And then, there’s LILO the bootloader. Not GRUB, mind! Feels a bit daunting, but then, if you’re careful and methodical, there should be no issues. That said, the approach automatically precludes Slackware from being a typical desktop choice, as most people would have no idea what to do with the installer.

    Continue reading

    Rang Gaeilge, 30ú lá na Márta 2022

    Duinnín agus Imleacán Kali

    Dineen and the navel of Kali

    Nodlaig, -lag, pl. -i, f. , oft. with art … .
    N. mhaith chughat, I wish you a merry Christmas…

    • Seachtain roimh Nollaig. An aimsir an-mhíthaitneamhach ar
      fad. Gálaí gaoithe, ráigeanna baistí, flichshneachta. An Duinnineach
      ar a bhealach isteach go hEaglais na mBráithre Bána. Bhí
      sé thart ar a haon agus ba léir go leanfadh an lá anfach, fliuch. I
      halla mór na hEaglaise, bhí go leor pramanna, báibíní ina gcodladh iontu,
      teachtaireachtaí carntha orthu. Bhí daoine, mná don
      chuid is mó de, ag rith isteach chun faoistine nó ag lasadh
      coinnle: ullmhú i gcomhair na Nollag faoi lán tseoil.

      Week before Christmas. The weather was thoroughly unpleasant. Gales of wind,
      sudden outbreaks of rain, sleet. Dineen was on his way to the WhiteFriars’ church.
      It was about one and it was clear that the rainy, wet day would continue.
      In the great hall of the Church, there were many prams, babies sleeping in them,
      messages piled on them. There were people, mostly women, running in to confession or lighting up candles: preparation for Christmas in full swing[sail].

      míthaitneamhach Displeasing, disagreeable; unpleasant, unattractive
      ráig udden rush; sudden outbreak; fit, bout, attack f pl ráigeanna
      flichshneachta sleet m
      anfach Stormy, rough, tempestuous
      teachtaireacht message f
      carn heap, pile v
      faoistin confession f
    • Léigh tuilleadh

    Rang Gaeilge, 23ú lá Mí Feabhra 2022

    Duinnín i Ráth Maonais (tuilleadh)

  • ‘Rachaidh mé féin anseo isteach, ‘arsa an Duinníneach nuair
    a shroicheadar an eaglais. ‘Ba mhaith liom cúpla focal a bheith
    agam le Tom Merrigan.’

    Tharla cruinniú coiste de chuid bhuanchoiste an aonaigh
    saothair ar siúl ar ardán an halla nuair a bhuail an Duinníneach
    isteach agus bhí an tAthair Merrigan ag déanamh eadrána idir
    seastán na gcístí agus lucht roth an áidh. Chuir sé na mná uaisle
    ar fad in aithne don Duinníneach, a gheall go dtiocfadh sé chun
    aonaigh agus go gceannódh sé stocaí bána cniotáilte uathu dá
    mbeidís ar fáil. D’éalaigh siad on gcruinniú ansin agus shiúil
    siad thart ar an halla, idir na stainníní, agus iad ag caint.

    ‘I’ll go in here myself,’ said Dineen when they reached the church.
    ‘I would like to have a few words with Tom Merrigan.’

    A meeting of the standing committee of the job fair was taking place on the hall stage
    when Dineen came in and Father Merrigan was mediating between the cake stand and
    the wheel of fortune. He introduced all the ladies to Dineen, who promised to come to the
    fair and buy white knitted socks from them if available. They then escaped from the meeting and walked around the hall, between the booths, talking.

    coiste jury, committee m
    buanchoiste Standing committee m
    ardán platform, stage, stand m
    eadráin Separation of combatants; intervention in dispute; mediation, conciliation f gs eadrána
    seastán stand m
    roth wheel n
    ádh luck m gs áidh
    lucht Content, charge; fill, capacity; cargo, load;
    Class, category, of) people
    m
    geall pledge, security m
    stainnín Stand, stall, booth m
  • Léigh tuilleadh

    More about Zoom under Windows

    As I wrote in September, my HP EliteDesk 705 G2 SFF desktop with an AMD PRO A4-8350B R5 processor was giving me messages about limited computer resources when using Zoom under Windows 10, though not under Linux. These sitll occur, even though I have added memory, taking it from 8GB to 24GB. This last time, I finally remembered to bring up Task Manager. It showed me that there was no memory problem, but that Zoom was using a lot of CPU. Why this occurs with Windows but not Linux is puzzling. For now I will have to have all of my Zoom sessions on that system under Linux rather than Windows.