You can go visit the proposal right now to get an idea of some of the questions and topics. Or even better, comment and contribute some of your own! If the idea of creating such a community appeals to you as it does to me, please take (literally) a few seconds to log in and follow the fledgling community. By doing this you show support for the idea and are speeding up the process of it becoming a full online community site.

Many unofficial sites that use the Stack Overflow software (the so-called Stack Exchange) system have also sprung up over the past months, perhaps the most active and well-known of these being Math Overflow. (Beware, however, the content is more than a bit scary unless you’re a post-graduate level mathematician!) This surge in popularity has even led to the creation of the Area 51 Stack Exchange site, which is a sort of officially-run staging ground for new Stack Exchange sites. (It does however require a strict process of definition, commitment, and beta testing before such communities are created as websites of there own.) Several communities are already on there way to becoming fully-fledged communities in the theme of Stack Overflow, for topics such as Web Applications, Cooking, Mathematics, and English Language.

What is more, a Physics proposal has been made for a Stack Exchange community, but is still only in its middle stages of creation. What it needs at the moment is what the creators of Area 51 term commitment (users stating that they intend to be active in the new community). No surprise then, that I’m advertising to the physics enthusiasts out there to go and sign up for the new community by committing. It takes no more time than signing in with your Google Account and clicking a button, but will give this community a real chance to develop into something great.

The popularity and sheer visitor count of the Stack Exchange and now the Area 51 websites should indicate that this could potentially be a very active and hugely useful community for physicists and physics students assisting each other in problems and sharing knowledge across the world. Unfortunately the existing attempt at a Stack Exchange community for physics over at physicsoverflow.net has shown little sign of taking off. Let us hope the two sites merge once things take off on the staging ground. Certainly, the process that Area 51 forces such sites to go through does however give every sign of success!

So, I thought I’d take this opportunity to share a brief list of some of the most clever/entertaining/useful apps I have on my iPhone at the moment. Not that anyone with an iPhone doesn’t already have enough, but it’s a handy reference list if you’re being picky about what to install, or browsing through streams of ratings! I’ve also thrown in a few iPhone/mobile-specific websites that are worth noting.

Information and Utilities

• Wikipedia/Wikipanion – pretty similar, but the former is a new official app, and the latter a slightly more established one
• Wolfram – great native interface for accessing Wolfram Alpha
• Google Earth – touch interface for Google Earth
• Tube Map – map and other utilities for London Underground
• Bloomberg – live updates and news for stocks, bonds, and currencies
• GraphCalc – advanced graphing and calculator for mathematical functions
• RedLaser – scans any bar code using camera and looks up best prices online
• iBooks – official app for downloading and reading books from the Apple store
• Stanza – download and read books, with interfaces for websites like Project Gutenburg
• IMDB – browse and view information about films
• Google Translate (website) – instantaneously translate text between any two languages

Media

• BBC iPlayer (website) – watch recent BBC shows anywhere for free
• TVCatchup Mobile (website) – watch UK FreeView channels anywhere for free
• NYTimes – best news app around, though it doesn’t cover local UK news of course
• BBC News – pretty useful app for UK and World news, though could do with a few usability improvements
• Remote – control iTunes on any computer within the local network
• Files (lite) – local file system for viewing images, Microsoft Office, and other files, can upload from anywhere in local network
• Dropbox – upload and download files from/to your space on the Dropbox.com service

Social

• Facebook – a great (and pretty complete) app for accessing Facebook, also an effective time sink!
• Skype – official Skype app, works alomost exactly like the normal phone app, and completely free
• Messenger – official MSN messenger app
• Google Talk – web app, accessible via the GTalk site
• Colloquy – IRC client

Fun and Games

• DoodleJump
• Angry Birds
• iChess
• Scrabble
• Physics Free

Note that most of these apps (and all of the websites) are completely free, though a few cost a small amount of money, typically no more than £1.

Pyotr Ilyich Tchaikovsky, by Nikolay Kuznetsov, 1893

The genius of Pyotr Ilyich Tchaikovsky is beyond doubt, yet the life and reputation of the man were often greatly troubled. (For that matter, it is hard to think of any great Romantic composer, from Beethoven to Schumann to Chopin, who did not have their fair share of life’s pains.) Not only was he constantly under attack for his homosexuality (which he tried constantly to hide), but his compositions were given a tough time even in his own country. It is not surprising that the portrait taken in his final year shows such a grave expression. His unique yet essentially Western European style was much resented by the the so-called Mighty Handful of contemporary Russian composers, who had different ideals (largely nationalistic). Later in the 20th century, his music was considered somewhat superficial and trivial, yet this view has since disappeared for the most part. His creative talents probably deserve more merit than the layman’s recognition of a few parts from The Nutcracker suite!

Tchaikovsky’s Slavonic March in B-flat minor (often given its French name, Marche Slave) is one of his minor works, but one that stands out for me. Emotionally charged, its mood varies from the sombre (reflecting the Russo-Turkish war of the time) to the hopeful, even cheerful. For sure, there is hardly a piece more evocative of Imperial Russia!

Download and Listen Here

(Performed by the Montreal Symphony Orchestra, 1999.)

View near the entrance of Fingal's Cave on Staffa in the Hebrides isles off Scotland

Felix Mendelssohn was a prolific composer of symphonies, concerti, operas, piano music, and songs, yet the Hebrides Overture stands out among all his works as one of the most beautiful and enchanting compositions of the era. Although you might classify it as a “concert overture”, its lyrical and emotive nature truly makes it unique among all pieces.

The style of Mendelssohn’s music was often criticised within his own lifetime as being too traditional and unadventurous (or even lacking in depth). Fortunately, the composer and his style has found much greater appreciation in recent decades. A curious fact, considering that he did so much to revive the works of J. S. Bach, himself a monumental composer whose music went out of favour for many years following his death. Undoubtedly, the predominance of his contemporary on the German music scene, Richard Wagner, who strongly voiced his antisemitism (Mendelssohn was born of Jewish heritage, despite later becoming a Christian), did nothing to help his popularity. Indeed, it strikes me as a great shame that himself and his music were disparaged so greatly during the 19th century, while arguably lesser composers such as Wagner were promoted. He did however find much popularity in Britain, hence his numerous visits to the island including Fingal’s Cave, situated in the Inner Hebrides, inspiring the piece that is the subject of this post.

Download or Listen Here

(Performed by the Musikkollegium Winterthur orchestra.)

• Permutations with repetition
• Permutations without repetition
• Combinations with repetition
• Combinations without repetition

Worth noting is that the algorithms run purely in-place on the list, and involve no recursion (only a single while loop). While memory usage is minimal, they do of course still run in factorial (or equivalently exponential) time complexity, though it’s well known you can’t do any better than that if you require all permutations/combinations of a given size.

Download the full (documented) code for the utility class here.

All four algorithms have been sufficiently tested and verified for small lists, running on .NET 4.0 (Windows). I would be inclined to bet everything runs perfectly well on Mono too. Needless to say, bug reports and feedback are welcome.

Of Rossini’s most notable operas, The Barber of Seville is surely right at the top. The aria from it that is commonly known as the Largo al Factotum is quite possibly one of the most recognisable arias in all opera. In this sense, I am somewhat breaking from the tradition of this series of posts, though for the sake of variety and because it would unfair not to mention a bit of opera when discussing Romantic music, I have included this piece in the series. Listening to this piece, you cannot but admire the extraordinary difficulty for the baritone singer, but also the wonderful meldoy that is created.

Download or Listen Here

(Sung by Nicolae Herlea. Original available from his official website.)

"Sonata Kreutzer", painted in 1901 by René François Xavier Prinet

Moving on into the Romantic period of music, it is only appropriate to begin with the great initiator of Romantic music, who is of course Ludwig van Beethoven. When I say romantic music, of course I do not refer to the romance of love, but rather to the philosophical and intellectual movement of Romanticism, which developed first in literature and art and later entered music. I have to confess that my love of Romantic music does as a whole outweigh that of Classical period. (Baroque music, on the other hand, being at least on par with that of the Romantic period, though it is somewhat unfair to compare them directly.) Its sheer variety makes it one of the fascinating genres, and its style is in many ways very modern (not surprising, considering it extended into the early 20th century and influenced almost every later style).

Beethoven’s Violin Sonata No. 9, better known as the Kreutzer sonata is perhaps one of the earliest and finest examples of Romanticism in music. Its association with passion and love, while not strictly related to it being a “Romantic” piece, becomes superbly clear once listening to it (in particular the first movement). This reputation is no doubt augmented by Leo Tolstoy’s short novel The Kreutzer Sonata.

Oh, and if you are feeling too impatient to hear out the whole piece, let me at least recommend listening to the first movement (around 10 minutes long), which is the true jewel of the work!

Listen or Download Here

(Performed by Paul Rosenthal and Edward Auer.)

As an incidental note, it is a quirk of history that this sonata is not in fact called the “Bridgetower Sonata”, since it was originally dedicated to the great violinist and Beethoven’s friend George Bridgetower. In fact, it was after the premiere that Bridgetower, whilst drinking with Beethoven, insulted a woman for whom Beethoven cared greatly, causing a rift between the two men, and hence the original dedication was removed and has since been forgotten.

The circumstances in which he composed this masterpiece are also shrouded in much myth, as he was working on it during the final days before his untimely death. (His friend and student Franz Xaver Süssmayr did in fact complete the work from Mozart’s drafts, though the first half or so of the mass is entirely Mozart’s own work.) Perhaps the greatest of these conspiracy theories is the one involving his supposed poisoning by Antonio Salieri (his great rival in Vienna), perpetuated in the play and film Amadeus, but very likely without basis. Others say he wrote this Requiem Mass for his own funeral, knowing he was to die soon. What is known for sure however is that he was commissioned by a mysterious stranger. In hindsight, it is thought likely that this stranger was Franz von Walsegg, an Austrian nobleman who had a habit of commissioning works from notable composers and passing them off as his own. Whatever the true circumstances, this work is surely a fine tribute the composer and his tragic death. Indeed, the Requiem Mass was played not only at his funeral (incompletely), but also at those of Haydn in 1809 and Chopin in 1849.

Since the piece is (unsurprisingly) rather long in duration – more or less an hour – I’ve selected several of the movements that I think showcase both the wonder and variation of the work.

Listen or Download:

Dies Irae

Lacrimosa

Agnus Dei

Lux aeterna

(Performed by the Schiller Institute Orchestra and Chorus, 1985.)

The complete performance is available to listen/download for free on the Schiller Institute website.

Having played around a lot with WPF recently (mainly as part of developing my little Windows 7 Film Browser app), I’ve found the need to create a variety of utility methods relating to WPF functionality. In particular, I’ve been finding certain utilities (helper and extension methods, that is) come in handy particular often, hence I thought I’d post them here to share with anyone who might find them useful.

You’ll have to forgive the lack of comments, but I’d rather hope the purposes of the methods are pretty clear anyway! Note that the class resides in the System.Windows namespace, so you’ll need to import that, in particular if you want to make the extension methods available.

using System;
using System.Collections.Generic;
using System.Linq;
using System.Text;
using System.Windows;
using System.Windows.Controls;
using System.Windows.Media;
using System.Windows.Media.Imaging;
using System.Windows.Threading;

namespace System.Windows
{
    public static class WindowsUtilities
    {
        // Useful for getting the item associated with the element clicked in a ListBox (generically any ItemsControl).
        public static object GetItemFromElement(this ItemsControl itemsControl, DependencyObject element)
        {
            return itemsControl.ItemContainerGenerator.ItemFromContainer(itemsControl.ContainerFromElement(element));
        }

        // Same as GetBounds method, but offsets bounds by Margin of element.
        public static Rect GetBoundsWithMargin(this FrameworkElement element)
        {
            var bounds = GetBounds(element);
            var margin = element.Margin;
            return new Rect(bounds.Left + margin.Left, bounds.Top + margin.Top, bounds.Right - margin.Right,
                bounds.Bottom - margin.Bottom);
        }

        public static Rect GetBounds(this UIElement element)
        {
            var window = Window.GetWindow(element);
            var position = element.TranslatePoint(new Point(0, 0), window);
            return new Rect(position, element.RenderSize);
        }

        public static Rect SubtractMargin(this Rect rect, Thickness margin)
        {
            return new Rect(rect.X + margin.Left, rect.Y + margin.Top, rect.Width - margin.Left - margin.Right,
                rect.Height - margin.Top - margin.Bottom);
        }

        public static TAncestor FindVisualAncestor<TAncestor>(this DependencyObject obj)
            where TAncestor : DependencyObject
        {
            var current = obj;
            do
            {
                if (current is TAncestor)
                    return (TAncestor)current;
                current = VisualTreeHelper.GetParent(current);
            } while (current != null);
            return null;
        }

        public static TAncestor FindLogicalAncestor<TAncestor>(this DependencyObject obj)
            where TAncestor : DependencyObject
        {
            var current = obj;
            do
            {
                if (current is TAncestor)
                    return (TAncestor)current;
                current = LogicalTreeHelper.GetParent(current);
            } while (current != null);
            return null;
        }

        public static IEnumerable<TAncestor> FindVisualDescendants<TAncestor>(this DependencyObject obj)
            where TAncestor : DependencyObject
        {
            var childrenCount = VisualTreeHelper.GetChildrenCount(obj);
            for (int i = 0; i < childrenCount; i++)
            {
                var child = VisualTreeHelper.GetChild(obj, i);
                if (child is TAncestor)
                    yield return (TAncestor)child;
                foreach (var subChild in FindVisualDescendants<TAncestor>(child))
                    yield return subChild;
            }
        }

        public static IEnumerable<TAncestor> FindLogicalDescendants<TAncestor>(this DependencyObject obj)
            where TAncestor : DependencyObject
        {
            foreach (var child in LogicalTreeHelper.GetChildren(obj).OfType<DependencyObject>())
            {
                if (child is TAncestor)
                    yield return (TAncestor)child;
                foreach (var subChild in FindVisualDescendants<TAncestor>(child))
                    yield return subChild;
            }
        }

        // This eliminates the slightly cumbersome task of casting a lambda expression to a delegate when calling Dispatcher.Invoke.
        public static void Invoke(this Dispatcher dispatcher, Action action)
        {
            dispatcher.Invoke(action);
        }
    }
}

The code was written as part of a WPF 4 (.NET 4.0) project, but I believe it’s totally compatible with WPF 3.5.

I’ll try to update to this post as my collection of handy utility methods grows (and maybe even add comments!). In the meanwhile, do feel free to suggest any improvements to the existing methods or even new ones that you find yourself using frequently.