Posted in science

Is pet food costing the Earth?

Have you ever wondered about your cat’s carbon footprint?

According to researchers at UCLA, meat eaten by cats and dogs in the US creates the equivalent of 64 million tons of carbon dioxide per year – the same climate impact as a year’s worth of driving from 13.6 million cars.

Livestock production required to meet overall US demand produces, on average, the equivalent of 260 million tons of carbon dioxide per year. Of this, between 25 to 30% can be chalked up to the meaty diet of cats and dogs. Currently, our fluffy friends consume around 25% of the animal-derived calories in the US. Incredibly, if the 163 million cats and dogs currently residing in America were to create their own furry country, they would rank fifth in global meat consumption.

Despite having the most pets per capita, this is not just an American issue. As of 2014, it was estimated that 24% of the UK’s population owned a dog and 18% owned a cat – percentages that are echoed by the majority of developed countries. Along with this, as emerging countries such as Brazil and China become more affluent, more people are purchasing pets.

Now, this isn’t to say that we should put our pets on a vegetarian diet. Indeed, doing this would be harmful and unhealthy for them. Getting rid of pets isn’t really an option either. Growing numbers of people consider their pets to be more like family members than animals, and it’s indisputable that pets provide both friendship and a wide variety of other social, health and emotional benefits.

So, how do we solve the problem?

Although the pet food industry is beginning to take steps towards greater sustainability, it will take a while to get there. In the meantime, you could consider getting a vegetarian pet such as a bird, hamster or rabbit in order to cut your carbon footprint.

Of course, if small animals aren’t really your cup of tea, you could always take Professor Gregory Okin’s advice and purchase a tiny horse. As he points out, ‘we’d all get more exercise taking them for walks, and they would also mow the lawn.’

Tabitha Watson

Posted in general, science, technology

Not feeling your selfie?

In a rather Black Mirror turn of events, researchers at the University of Waterloo have developed an app that will tell you how to take ‘the perfect selfie’.

To help you capture your best angle, the app uses an algorithm to direct the way you position the camera.

In order to decide on the ‘best’ angle, the researchers used 3D digital scans of a collection of computer generated people. Then, after taking hundreds of virtual selfies – each with different composition and lighting, an online crowdsourcing service was used to get thousands of people to rate the selfies as either ‘good’ or ‘bad’. These voting patterns were then mathematically modelled in order to develop the algorithm.

To check that the app worked as it should, the researchers had real people take selfies with and without the computerised aid. Based on the subsequent online ratings, a 26% improvement was seen in selfies taken with the app compared to a normal phone camera.

‘We can expand the potential to include variable aspects such as hairstyle, types of smile or even the outfit you wear,’ says Dan Vogel, one of the scientists involved in the development of the app.

Tabitha Watson

To see the app in action, click here.

Image credit: [http://images.shape.mdpcdn.com/sites/shape.com/files/styles/story_detail/public/selfie-study-promo.jpg]

Posted in chemistry, science

The perfume conundrum – why it smells different on different people

I’m sure you’ve noticed that perfume never smells the same on any two people, a fact that can be jolly frustrating when you’re out shopping for a new scent. Something that smells divine in the bottle or when worn by a friend can easily seem cloying and repugnant once applied to your skin. So, why do these variations occur?

Well. As you would expect, it all begins in the nose. Our sense of smell is dependent on a small patch of specialised olfactory sensory neurons located high up in the nasal cavity. This patch is called the olfactory epithelium, and it is covered by a carpet of olfactory receptors. On average, humans tend to have around 450 different types of olfactory receptor, each capable of binding to a wide array of odour molecules. Unlike conventional receptors which only bind to one type of thing, olfactory receptors can be activated by many different molecules (and each molecule can activate many different receptors). Each molecule/receptor combination binds in a slightly different way, and these differences provide us with our nuanced sense of smell. In fact, your sense of smell is probably better than you think – researchers at Rockefeller University have found that humans are capable of detecting over one trillion individual scents.

Due to natural variation, different people have a different number and combination of olfactory receptors. This leads to different experiences of smell. Someone could find the aroma of patchouli in a perfume overpowering, whilst another may not be able to detect the scent at all. Whilst this difference in interpretation is certainly a part of the puzzle, it doesn’t explain why the same perfume smells different on different people. Don’t worry – I’m getting to that bit.

As you may know, each individual has a unique ‘skin chemistry’. This is influenced by a great deal of factors ranging from temperature, humidity and sweat composition to the types of medication you’re taking and the range of aromatic herbs in your diet. In some circumstances, your skin chemistry can alter by the hour. When you apply perfume, the naturally occurring chemicals on your skin mingle with those present in the perfume, creating a subtly different scent. The environment you’re in can also influence your perception of a smell – sampling a perfume in someone’s bedroom will often be an entirely different experience to testing a new brand at your local shop.

Along with the influence of your skin chemistry, the time after application can also have an impact on your perception of a perfume or cologne. Each concoction tends to be made up of three different ‘notes’ – top, middle and base. The top notes are the ones you smell immediately after application (their small and volatile structures evaporate easily and float straight towards the nose). The middle notes are next, emerging after around two hours due to their larger molecular weight. The base notes are the last to appear, a good five hours after initial application. They are the largest molecules, so require prolonged exposure to body heat in order to evaporate.

So, here we are. After a bit of discussion, it seems like the differences in perfume experience are due to a wide range of factors. Not only does your individual nose play a part, but so does the garlic bread you had for lunch and the weather that day. Pretty pot-luck, eh?

Tabitha Watson

Image Credit: [http://mac.h-cdn.co/assets/15/51/980×490/landscape-1450470504-best-perfume.jpg]

 

Posted in physics, science

How do headphones work?

With a market value set to reach $15.8 billion by 2025, chances are you own a pair of headphones. However, the odds of the average person knowing how they work are significantly worse.

At the most basic level, all speakers are made up of three main constituents: a cone (sometimes referred to as a diaphragm), a coil of wire and a permanent magnet. As shown in the main image, the cone is attached to the coil. The permanent magnet is situated within the coil.

Electricity is fundamental to the function of headphones – when it flows through the coil, it becomes an electromagnet. If the flow of the electricity is altered, the electromagnet either attracts or repels the permanent magnet. This combination of both attraction and repulsion induces motion in the coil, causing the cone to move. These movements generate vibrations (a.k.a. soundwaves) in the air – much like those produced by banging on the skin of a drum. As discussed in my previous post ‘How do we hear?’, the ear detects these vibrations and converts them into signals that can be processed by the brain.

Once the soundwaves are being produced, factors such as volume and pitch are controlled by the strength and frequency of vibration. In order to generate a louder sound, larger and more powerful vibrations are required. Pitches are determined by the frequency of the soundwave. The frequency is defined as the rate of the wave, illustrated by Figure 1. Whilst pitch is altered simply by increasing the power of vibration, frequency is governed more by the size of the speaker. Hence, huge subwoofers produce much better bass than a tiny in-ear headphone.
frequency1

Figure 1

Although humans are capable of hearing many different types of sound, headphones and other sound-systems can typically only produce two: monoaural and stereo. Monoaural is when the sound only comes from one source, such as someone speaking. This is the type of sound encountered during a phone conversation or from an old radio. Stereo sound is encountered when two speakers generate slightly different vibrations in order to emulate a 2D soundscape. Have you ever had a song begin in one headphone and move across to the other? That’s an example of stereo. Whilst it is possible to generate 3D sound artificially, it is a lot more time consuming. To be effective, speakers must be placed around the audience and each must play subtly different things. Currently, the only place that this is practical is for ‘surround-sound’ in cinemas. Though, given the passage of time, it may well become a future household staple.

Tabitha Watson

Image Creds: [http://www-cdn.sciencebuddies.org/Files/7472/6/speaker-diagram.png

images.tutorvista.com/cms/images/83/frequency1.PNG]

Posted in biology, science

How do we hear?

In order to hear the world around us, humans and other mammals rely on vibrations travelling in the air. To interpret these vibrations, the ear has evolved a complex system of canals and tiny hair-like protrusions, all working in harmony to generate sound as we know it.

The ear is a complex structure composed of three distinct parts, each with separate functions. The outer ear (or pinna) is the external section that protrudes from the side of the head. Responsible for the placement of sounds in relation to our bodies, the complex arches and valleys funnel vibrations into the ear canal and create a three dimensional soundscape.

Once the vibrations begin to move down the ear canal, they enter the middle ear. This section is composed of the auditory canal, which terminates at the eardrum (also known as the tympanic membrane). The eardrum is then attached to three tiny bones called ossicles, surrounded by a small pocket of air. Individually, these bones are the malleus, incus and stapes (or alternatively, the hammer, anvil and stirrup). The ossicles are then attached to a fluid-filled structure called the cochlea. It is here that the inner ear begins.

The primary function of the cochlea is to convert vibrations into electrical impulses to be sent down the auditory nerve and interpreted by the brain. In order to change the vibrations to impulses, a rather ingenious method is employed. Once the vibration reaches the cochlea from the ossicles, it travels down the basilar membrane whereupon it is detected by approximately 16,000 to 20,000 hair-like cells called cilia. These cilia are attached to a specialised part of the ear canal called the Organ of Corti, and it is here that the raw vibrations are converted to nerve impulses and passed along the auditory nerve to the brain. This is achieved by the deformation of the cilia – as they are moved by the vibrations, specialised ion channels are pulled open and the resultant influx of potassium and calcium ions depolarises the cells and produces an action potential.

So how are humans able to hear such a spectrum of different sounds and pitches? Well, it’s all down to the tapered shape of the cochlea. Due to their individual amplitudes, different frequencies of sound wave peak at different times as they travel down the ear canal. As higher frequency waves have larger amplitudes, they are not able to travel as far as lower frequency waves. Due to this, each section of cilia is sensitive to a particular frequency of wave – this is what enables the detection of such a vast spectrum of sound.

Tabitha Watson

Image Credit:

[http://dt7v1i9vyp3mf.cloudfront.net/styles/news_large/s3/imagelibra/E/Ear_01.jpg?W0hbNd_Wzq4sD071RFwOhUnzgBMQHi22=&itok=VJ-3sBGY]

Posted in chemistry, physics, science

How do things glow in the dark?

It is relatively common nowadays to see a plethora of glow-in-the-dark products across a vast spectrum of items. Although most regularly found in toys and watches, there seems to be no end to the types of item that can be modified to glow. So, how does this phenomenon occur?

Firstly, it is important to pin-point what is meant by the term ‘glow-in-the-dark’. In this instance, it is used to describe luminescence. Luminescence is the emission of light from a source that has not been heated; due to the lack of heat, it is a form of spontaneous emission. If heat is involved, then the phenomena is labelled incandescence and is not considered spontaneous. There are several different ways in which luminescence can occur, including through chemical reactions, electric currents and the compression of certain types of crystal.

The type of luminescence encountered most commonly in day-to-day products is phosphorescence. Phosphorescence is a specific type of photoluminescence that involves molecules called phosphors. Usually transition metals or rare earth elements, phosphors absorb energy from electromagnetic radiation and emit it as visible light over timescales between nanoseconds and hours. Funnily enough, phosphorus is not defined as a phosphor – it is chemiluminescent as opposed to photoluminescent.

Underpinning the ability for photoluminescent materials to emit light is quantum mechanics. When a photon collides with the phosphor and is absorbed, it excites an electron to a higher transition state. When the electron drops back down to its usual state, it releases a photon whose energy exactly corresponds to the size of the gap between the levels. This is what we perceive as the emitted ‘glow’. In the majority of photoluminescent events, this excitation and relaxation of electrons occurs over extremely short timescales, often in the region of nanoseconds. This is known as fluorescence. However, when phosphors (such as zinc sulphide and strontium aluminate) are involved, phosphorescence can emit light over much longer periods of time. This is the key difference between fluorescence and phosphorescence – the time taken to re-emit the energy.

So, why is it that phosphorescence can occur over such long timescales? Again, it’s all based on quantum mechanics. As you may know, ‘allowed transition states’ and ‘forbidden transition states’ are key within quantum mechanics. These, along with a rather expansive set of rules, govern the movement of electrons in their respective shells. In normal circumstances, when a ground state electron is excited to a higher energy level, it will transition into an exited singlet state. This means that it has paired up with another electron with an opposite spin (i.e. obeying the Pauli Exclusion Principle). The Pauli Exclusion Principle states that no two particles with a half integer spin (such as electrons) can occupy the same orbital at the same time (think of people on a bus – ideally, people aim to sit on an unoccupied pair of seats before going to sit next to a stranger).

However, in some cases (as in phosphorescence), the excited electron will transition into an excited triplet state. This is where things get a little complicated. In an excited triplet state, the excited electron is spinning parallel to the ground state. This is called intersystem crossing. As having the same spin is considered ‘forbidden’ within quantum mechanics (again, due to our friend Pauli), it means that the excited triplet state electron is in a bit of a pickle. The ‘forbidden’ transitions are less kinetically favourable than the ‘allowed’ transitions, meaning that it is more difficult for the electron to relax back to its normal ground state. This prolongs the relaxation progress, ensuring that the glow of released photons lasts for longer.

So, there it is. Objects glow in the dark due to the phenomena of phosphorescence – the process by which electrons are excited to ‘forbidden’ quantum spin states. As the electrons are allowed to relax, they emit a photon of light corresponding to the distance between the energy levels, producing the subtle glow which is now associated with watch hands and plastic stars. In conclusion, the entire glow-in-the-dark industry is reliant upon a small group of rebellious electrons not doing what they should. Pretty neat, huh?

Tabitha Watson

Posted in biology, science

Is napping bad for you?

Unfortunately, it is often the case that the most enjoyable things in life are also the worst for you. Sweets, coffee, alcohol; the list seems endless. One of the most enjoyable things in life (at least for a student), is a cheeky nap after a particularly trying lecture. However, is it good for you?

There is conflicting evidence surrounding the concept of napping – some suggest that a brief siesta after your 9am lecture could help you lose weight and even boost brain activity, whereas others think that too many naps could increase an individual’s risk of developing Type 2 diabetes. So, which is the truth?

A study conducted at the University of Tokyo in Japan found that those who napped for longer than an hour per day were 45% more likely to contract Type 2 diabetes than those who did not nap or who napped for less than an hour. Despite this seemingly damning evidence, all is not lost for those who enjoy a longer snooze. It is very likely that the data gathered by the Japanese research team could have been influenced by external factors not recorded in the distributed questionnaire – in fact, it is almost certain. A more recent research project presented at the European Association for the Study of Diabetes suggested that the correlation between obesity and napping is likely to have influenced the apparent link to diabetes. They argued that the existing obesity epidemic and not the act of napping itself was to blame for the raised diabetes risk.

The claim that napping can help with weight loss can also be swiftly debunked: on average, people who sleep around 5 hours per night tend to gain less than 2kg of weight per year, which is on par with those who sleep around 7 hours per night.

After examining both sides of the argument, it appears that napping is a fairly neutral pastime. When the evidence is weighed up, the correlations between extra sleep and the proposed health benefits and/or detriments seem to be built on rather spurious connections, vastly influenced by external variables. Finally, a pleasure that can be enjoyed sans-guilt.

Tabitha Watson

Image Credit: [https://i.kinja-img.com/gawker-media/image/upload/s–1FvmwsTr–/c_scale,fl_progressive,q_80,w_800/191dbvjco20mbjpg.jpg]

Posted in science

What causes colour-blindness?

Colour-blindness is a relatively common human condition – 8% of men are born colour-blind, as are 4.5% of women. This discrepancy between the genders is due to the gene linked to colour-blindness being on the X chromosome (i.e. women inherit two copies so both of the inherited genes must be faulty for them to be impacted). That being said, although the majority of cases of colour-blindness are genetic, a percentage of people can develop colour-blindness later in life. Colour vision tends to decline past the age of 60, and ill-managed chronic conditions such as diabetes, strokes, chronic alcoholism and Parkinson’s disease can all lead to eventual colour-blindness.

So what exactly causes people to be unable to see colour? It’s all linked to the many complex structures within the eye. There are two main light-sensitive cells within the human eye, both found in the retina. These cells are rods and cones. Both are found in vast numbers – in each individual retina there is in excess of 90 million rods and between 6 to 7 million cones. Despite their apparent similarities, rods and cones have very different and distinct roles when it comes to detecting light and processing images.

Rods are able to function in less light and are more sensitive than cones, and therefore they are mainly used for night vision. They are capable of responding to a single photon of light, making them around 100 times more sensitive than cones. However, they only contain one type of colour pigment. Rods are concentrated around the outer edges of the retina, and are used in peripheral vision during the daylight. However, as there are so many rod cells in the retina, multiple cells tend to share a neuron in order to amplify their signals. This makes the resolution of images detected by rods much less clear.

Despite there being many, many fewer cones than rods, they are responsible for much of the clarity of colour we experience. The exact opposite to rods, they function best in bright light. Three different varieties of cones are found in the retina of typical humans, L-cones, M-cones and S-cones. This means that as a species we are said to have ‘trichromatic vision’. Each different type of cone detects a different wavelength of light, and these wavelengths combine to give the large spectrum of visible colour seen by the majority of people. This range varies from species to species – amazingly, it has been reported that some types of snake can observe some wavelengths in the infrared spectrum.

There are three main pigments in the eye that allow us to observe colour, and – bizarrely enough – they vary from person to person due to genetic mutation and other factors. This means that everyone sees colour differently.

This intricate network of different receptors and pigments within the eye is very fragile, making it susceptible to damage and mutation. If a combination of rods and/or cones are faulty, then not all wavelengths of light can be absorbed. This leads to some colours appearing differently to the affected person, or perhaps not appearing at all. The most common form of colour-blindness is ‘red-green colour-blindness’. This is an umbrella term for people with either deuteranomaly or protanomaly. This is caused by one type of cone being slightly faulty, which causes the spectrum of visible colour to shift, rendering some colours slightly out-of-whack.

However, my parting thought is this: as no-one sees colour in exactly the same way, who’s to say who’s version of colour is correct?

Tabitha Watson

Image Credit: [http://www.colourblindawareness.org/wp-content/themes/outreach/images/slider/types/xeye.jpg.pagespeed.ic.mmcI6be7ml.jpg]

Posted in science

Why do leaves change colour?

The changing colours of the leaves is many people’s favourite part of autumn – the gorgeous hues are pretty much synonymous with the changing of the seasons. There is so much variation as well; many trees display a wide array of yellows, golds, oranges, reds and everything in-between. So, what causes this transformation to occur?

As the days get shorter and darker, there is less light intensity falling on the leaves of trees. This reduced light intensity initiates the breakdown of chlorophyll, a green pigment which is responsible for absorbing light to facilitate photosynthesis. As the chlorophyll begins to break down and be removed from the leaves, other pigments start to become visible. Funnily enough, it is these secondary pigments that cause the vibrant (and picturesque) autumnal colours. The main compounds which are revealed are xanthophyll, carotene and anthocyanins. Xanthophyll and carotene are responsible for the more orange shades, and any red colours are attributed to the anthocyanins.

At the same time as the chlorophyll is being broken down, a specialist layer of cells named ‘cork cells’ build up at the base of the leaf. These cells shut off the veins in the leaf from the rest of the tree, forming a leaf scar which protects the overall plant when the leaf is eventually severed.

The overall colours of the leaves are determined by a combination of environmental factors. Light intensity, temperature and the abundance of water all play roles. For example: the colder the temperature, the redder the leaves. This is due to the anthocyanins being more visible.

Currently there are two main theories as to why leaves change colour; photoprotection and coevolution. The idea behind the photoprotection theory is that as the chlorophyll breaks down and exposes more anthocyanins, they are then able to protect the leaves from damage caused by high light intensity at low temperatures. This helps to reduce photo-oxidation and photo-inhibition, therefore (theoretically) making the reabsorption of nutrients more efficient.

The coevolution theory states that the brighter red the leaves turn, the more toxic the tree is to certain types of insect. This would act as an indicator to the creatures affected, reducing the parasite load of the tree for the onset of winter. Equally, the vibrant colours could attract certain types of insect or bird. This said, neither of these theories has been fully proven, and neither of them provide a justifiable explanation as to how the colour change links to the inevitable dropping of the leaves.

So, to conclude: the fantastic autumnal colours of leaves are produced as chlorophyll breaks down, and no one fully understands why this occurs.

Tabitha Watson

Image credit: http://www.mrwallpaper.com/wallpapers/Autumn-Leaves-Background-851×315.jpg