I’m used to working with wood, but I had no experience with epoxy. I made many mistakes, but that’s how I learn. You might watch the relaxing river table videos on the internet; I could have filmed my work too, but it was far from relaxing.

First, I had to get wood.

I bought two oak slabs, each about 2.50 m long, from someone online. They didn’t fit in my car, so I had to drive with the trunk half open, which provided great ventilation during the hot summer.

This is what I got:

I cut both slabs to 150cm.

Formwork

The next step was constructing the formwork (or mold). The formwork is essentially a container that holds the wood slabs and contains the liquid epoxy resin, preventing any leaks until it cures (at least in theory; we’ll see about that later).

On the base of the formwork, I sketched out a plan:

And here is the completed formwork:

I applied a layer of tape between the wood slabs and the formwork base to prevent the epoxy from sticking. To prevent leaks, the sides of the formwork were screwed securely into the base and everything was sealed with a thick silicone joint.

Epoxy

Once the formwork was finished, it was time to mix and pour the epoxy. I added a blue dye to the epoxy.

And here was my first mistake: The wood slabs were not flat, and the epoxy leaked out of the formwork.

Eventually, the epoxy cured and fixed the leaks, but by then, most of the epoxy had already dripped onto the ground. Something the relaxing river table videos don’t usually tell you is that epoxy resin is very expensive. You might have noticed a few clamps on the left; that was another attempt to contain the leaks.

While the first layer of epoxy cured and fixed the leaks by effectively sealing all the gaps, I bought another batch and poured a second layer.

The white and blue tape on the top was intended to prevent epoxy from running all over the wood. Looking back this was my second mistake, it would have been so much easier to pour a thin layer over the wood slabs, since I ended up with some wood sections with epoxy and others without, which was a pain to sand.

Somehow I suspected there would be leaks and I had already put a plastic layer on the ground. The last thing I needed was to scrape epoxy off the concrete.

Sanding / varnish

Anyway, once the epoxy was mostly cured, it was time to sand and varnish the wood.

I started by sanding the wood, progressing from coarse grit to fine ones. While this process took a long time, with a good sander it’s fine. I then put a few layers of varnish on the wood to protect it.

Here, you can see the wood finished, but the epoxy remains untouched:

A few people told me to remove the live edge because it eventually falls away; however, I didn’t listen. I sanded it a bit and varnished it, though.

I also sanded the epoxy the same way.

Legs attempt 1

The first attempt at the legs was out of metal. Unfortunately, the legs were bending under the weight of the table.

The interesting part here is the view under the table, where we can see the epoxy that leaked. I spent a lot of time trying to get rid of that epoxy but eventually decided it’s not worth the effort. Even some of the formwork base remained stuck to it.

Polish

Once the wood was protected with a layer of varnish, it was time for polishing. I polished with my drill because it worked well and I was too lazy to use the right tools.

Final result

In the end it looks like this:

I learned a lot.

Would I do it again? Not with epoxy. It’s expensive, overrated, and not too pleasant to work with; curing takes a long time and the material is very hard.

That said, here are my takeaways:

• Level your wood slabs before pouring.
• Pour a thin sealing layer of epoxy on top of the wood.

Mailway is an email forwarding service I launched two year ago (December 2020). To learn more about the service please visit the website: Mailway.

The stack is about the following: all email services are written in Golang, the routing configuration is stored in Workers KV, the dashboard uses Cloudflare Workers and the frontend is using React.

See the complete technical architecture.

It’s now time for the service to sunset.

User base

At the time of writing, the numbers are the following:

• 516 users

Alternative

I recommend using Cloudflare’s Email Routing service as an alternative.

Speed of light

The speed of light in a vacuum (denoted as \(c\)) is: \(299,792,458\) metres per second.

Refractive index

The speed of which light propagates through transparent materials will be is less than \(c\), by a coefficient called refractive index.

The formula to calculate the speed given a refractive index (called \(n\)) is: \(v = c/n\).

Air (at standard temperature and pressure) has a refractive index of \(1.000273\), meaning that light can only travel at \(\approx 299,710,637m/s\) which is \(\approx 82km/s\) slower than \(c\).

See list of refractive indexes per materials.

Optical fibers

Fibers are made from the following materials: Silica, Fluoride glass, Phosphate glass and Chalcogenide glass. Their respective refractive index are 1.458, 1.51, 1.701 and unknown. Note that I can’t guarantee that these measurements were done in the same conditions.

These materials range from \(\approx 94,173km/s\) to \(\approx 123,548km/s\) slower than \(c\), or approximately \(\approx 2/3\) of \(c\).

Repeater

Optical fibers over a long distance need to be repeated every few 100km to combat light attenuation. Near-infrared wavelengths are generally used because this wavelength has the lowest attenuation rate.

Note that each repeaters require power which is routed through the cable.

Apollo example

Apollo transatlantic submarine cable system (now owned by Vodafone).

Based on submarinenetworks.com the Apollo cable network uses Alcatel-Lucent’s 1620 Light Manager (LM).

It supports WDM but for the sake of example let’s only consider the band 2:

• Frequency: \(195.3125 GHz\)
• Wavelength: \(1534.937 nm\)

I have no idea what type of fiber Apollo uses but let’s use Corning® SMF-28® as an example. Which with a wavelength of \(1550 nm\) has a refractive index of \(1.4682\).

One particular path called Apollo South has a length of \(\approx 5,582km\).

The maximum theoretical speed is \(\approx 204,190,477m/s\) (again, approximately \(\approx 2/3\) of \(c\)), it takes \(~27ms\) for the light to cross the ocean. This is excluding any light repeaters or network equipment on the way.

Radio

As a side note, it’s possible to communicate between similiar distances closer to \(c\) using various radio frequencies, as the radio waves travel through air instead of fibers.

This technology is mostly used for trading and comes with its own problem, see kc1ght.com’s article for more information.

Poste proposé: temps plein

Contexte

Les Hôpitaux Universitaires de Strasbourg (HUS), établissement de référence du Grand Est classé parmi les premiers CHU français, ont une triple mission de soins, d’enseignement et de recherche. Ils se composent de 5 sites hospitaliers, organisés en 21 pôles d’activités cliniques et médicotechniques, et comptent 2 750 lits et places, 1 pôle logistique ainsi que 7 écoles et instituts de formation. Avec plus de 11 850 employés, professionnels médicaux et non-médicaux, le centre hospitalier régional universitaire de Strasbourg est le premier employeur d’Alsace.

Au sein des HUS, le Groupe Méthode en Recherche Clinique (GMRC), équipe pluridisciplinaire de 10 personnes, rattaché au Pôle Santé publique, santé au travail et hygiène hospitalière, est une structure support pour tous les personnels souhaitant mener des recherches cliniques ou des recherches épidémiologiques. Le GMRC intervient aux stades d’écriture du protocole, de soumissions aux instances réglementaires ou aux demandes de financement, d’analyse et interprétation des résultats de l’étude, de rédaction des articles et communications scientifiques. Le GMRC est spécialisé dans la méthodologie des études et en sciences des données pour la réutilisation de données de santé.

Profil recherché

Nous recherchons un biostatisticien polyvalent dans l’analyse des études cliniques et la sciences des données.

De formation Bac+5 en informatique, diplômé d’une école d’ingénieur, d’un master universitaire spécialisé en technologies de l’information, d’un master en statistique dans un parcours de biostatistique ou d’une formation équivalente assortie d’une expérience professionnelle minimale,

• vous êtes à la recherche d’un nouveau challenge qui fait sens dans secteur de la santé,
• vous êtes passionné par le traitement des données de santé et éventuellement disposez d’une première expérience réussie dans ce domaine,
• vous avez déjà utilisé le langage R
• vous travaillez avec des bases de données relationnelles et maitrisez SQL
• vous êtes curieux et force de proposition

ce poste est fait pour vous!

Vos missions

Au sein du GMRC, le biostatisticien participe à la conception des méthodologies biostatistiques utilisées dans les projets qui lui sont confiés. Il est en charge, suivant le plan d’analyse statistique du protocole, des analyses des données et participe à la rédaction des communications scientifiques. Il travaille en collaboration avec les acteurs de chaque projet (cliniciens, épidémiologistes, chercheurs, data-manager…). D’autre part, le biostaticien participera à la montée en charge de l’entrepôt de données des HUS.

Plus spécifiquement, le biostatisticien:

• aide à la formulation des hypothèses de recherche d’une étude et au choix du plan expérimental, calcule le nombre de sujets nécessaires ou la puissance, participe aux choix des méthodes et techniques statistiques appropriées, rédige les plans d’analyse statistique, programme les analystes statistiques dans R;
• participe à l’élaboration des plans de data management nécessaires aux études en lien avec le datamanager;
• met en oeuvre le plan d’analyse statistique, rédige un rapport d’analyse et une synthèse des résultats;
• participe à la valorisation des travaux réalisés (résumés pour des congrès, rédactions d’articles scientifiques);
• assure une veille scientifique des méthodes statistiques les plus adaptées aux données traitées;
• participe aux travaux de recherche du GMRC et à des échanges entre biostatisticiens.

Particularité du poste:

• accès à des données médicales confidentielles;
• mise en oeuvre de l’entrepôt de données de santé des HUS et premiers travaux utilisant les techniques de science des données et traitement automatique du langage;
• accès et utilisation du Système national des données de santé (SNDS).

Vos compétences

• Maîtrise des méthodes statistiques;
• Maîtrise du data management nécessaire pour les analyses statistiques;
• Bonne maîtrise du logiciel statistique R, et éventuellement de SAS, des requêtes SQL;
• Connaissance des méthodes de machine learning;
• Maîtrise des outils bureautiques et de communication (Excel, Word, Powerpoint);
• Maîtrise de l’anglais scientifique.

Vos qualités

• Vous avez envie de mettre vos compétences aux services de la santé;
• Curieux, vous cherchez à comprendre les problématiques métier (médecine hospitalière);
• Vous savez être autonome et, si besoin, prendre des initiatives, notamment dans la recherche de solutions
• Vous aimez travailler dans des équipes pluridisciplinaires et vous adapter;
• Vous disposez d’un bon esprit d’analyse et de synthèse;
• Vous savez vous conformer à l’organisation et au fonctionnement de la structure et respecter le secret professionnel.

Ce poste vous intéresse? contactez le Pr Erik-A. SAULEAU: erik.sauleau@chru-strasbourg.fr.

Mailway is an email forwarding service I launched a year ago (December 2020). To learn more about the service please visit the website: Mailway.

The stack is about the following: all email services are written in Golang, the routing configuration is stored in Workers KV, the dashboard uses Cloudflare Workers and the frontend is using React.

See the complete technical architecture.

User base

At the time of writing, the numbers are the following:

• 417 users
• 331 domains are pointing to Mailway MX servers (meaning they are active)
• 234 domains haven’t been activated yet

Emails metrics

In average 1647 emails were received per day during the past 2 weeks:

Self-hosted instances

Mailway’s service can be self-hosted. Currently 45 self-hosted instances have been created but we don’t have any visiblity into them.

The Mailway Docker image has been pulled more than 10K times.

Reliability

Since the launch, we had no major outages. Partly thanks to Mailway’s design.

During the last month the API’s availability was good:

While working on mailway.app I experimented with routing emails based on SNI.

Let’s imagine a common email setup:

• sauleau.com has a MX record that points to mx.sauleau.com.
• mx.sauleau.com has an A record that points to an email server’s IP.

When someone sends an email to hello@sauleau.com, it needs to resolve the MX record and the A record to find the corresponding email server.

Traditionally, mx.sauleau.com would run on its dedicated email server and listen on port 25. To run a secure email server we have a TLS certificate stored on the server issued specifically for mx.sauleau.com.

The certificate is presented to anyone connecting to the IP and asking for a secure connection. Which implies that it’s not related to the hostname we used to resolve the IP (A record), more importantly, most clients will abort if the TLS certificate doesn’t match the hostname it attempted to connect to.

To address this issue we could use SNI since it appears earlier in the SMTP communication with the email server and allows to select a TLS certificate to present to the client, which would use the right hostname. However, not all email clients support sending the SNI.

Email providers support

Once upon a time

My domain xtuc.fr is very likely the first domain I ever bought, it was registered on the 2010-07-07T14:08:06Z.

Over the years my old domain has served many purposes, but it's not in use for a while now.

Anyway, it's just a domain...

The spam

The emails are mostly noise (aka spam); AWS or Facebook notifications, wordpress.com subscriptions, old mailing lists, or whoever bought a list that included it, online forums, etc and from time to time I see something interesting.

Interestingly, I didn't register a Facebook account with that email nor do I subscribe to hundreds of Wordpress blogs.

Mailway

Note that I'm using mailway.app here, but other similar services should work as well.

Here is a screenshot of the routing rules I have configured:

The result that is many emails are dropped before they can reach my inbox, even if they will likely be moved to the spam folder.

Here's the result after a week:

Conclusion

Even if the emails mostly went to the spam folder, it greatly improved the signal-to-noise ratio which made it possible to catch interesting emails.

Status of all features

More details

More information are available on the GitHub repo.

Background

JavaScript’s Number type is a float64 and is limited to 53 bits of actual value (as specified by IEEE 754).

Wasm offers a 64 bits integer type, there’s currently no efficient way to represent this type in JavaScript, which can be limiting.

JavaScript recently introduced the BigInt object, allowing the representation of arbitrary length integers.

Performance

The BigInt interpretation inevitably introduce an overhead, however the conversions happen only at the JavaScript boundaries. The i64 is then used directly in Wasm, which has no overhead.

Under the hood - v8

You can see the CL I made here: https://chromium-review.googlesource.com/c/v8/v8/+/1355144.

        
(module
  (func export 'fn') (result i64)
    (i64.const 66)
  )
)
        
      

        
(module
  (func (export 'fn') (param i64) (result i64)
    (get_local 0)
  )
)
        
      

In this article I will focus on the usage in Webpack but if you want to learn about writing WebAssembly (using the text format) you can read this great article: Writing WebAssembly By Hand.

        
module.exports = {
  entry: "./index.js",
  module: {
    rules: [
      {
        test: /\.wast$/,
        loader: "wast-loader",
        type: "webassembly/experimental"
      }
    ]
  }
};
        
      

        
import("./add.wast").then(({add}) => {
  console.log("add", add(1, 2));
});
        
      

        
(module
  (func (export "add") (param i32 i32) (result i32)
    (get_local 0)
    (get_local 1)
    (i32.add)
  )
)
        
      

        
(module
  (import "./file.js" "n" (global i32))

  (func (export "getn") (result i32)
    (get_global 0)
  )
)