Friday, 25 April 2014

Mari Mengenal Lintah Dengan Lebih Dekat!



Sekali pandang pada lintah-lintah, reaksi wajah terus berkerut kerana 'geli' melihat struktur kulitnya yang licin lalu akan berundur setapak ke belakang mengelak dari menyentuhnya.

Secara amnya, lintah boleh dijumpai di dalam air tawar dan air laut. Ia adalah haiwan jenis hermafrodit iaitu mempunyai kedua-dua organ jantan dan betina. Terdapat satu bahagian penghisap darah pada mulut lintah yang dikenali sebagai 'penghisap anterior'. Lintah berpaut pada perumah seperti manusia dengan penghisap anterior dan akan mengeluarkan sejenis bendalir seperti bius yang menyebabkan perumah tidak menyedari hinggapan lintah. Lintah berpaut pada manusia untuk menghisap darah sehingga kenyang. Kemudian ia akan turun dari perumah untuk menghadam makanannya. 
Pada kebiasaannya, kita akan terkejut dan menjerit-jerit sekiranya melihat lintah melekat pada badan kita. Kita akan terus menarik lintah untuk membuangnya. Tetapi, tahukah anda bahawa lintah boleh memanjangkan badannya sehingga kebuh kurang 30cm panjang. Sekiranya ia ditarik terlalu kuat, bahagian penghisap anterior mungkin akan tertinggal pada badan kita.  Lihat video di bawah!

video
Sungguhpun haiwan ini menggelikan, ia mempunyai manfaat lain dalam bidang perubatan. Lintah atau nama saintifiknya Hirudo medicinalis boleh mengeluarkan bahan hirudin, iaitu sejenis protein yang berfungsi sebagai agen anti-pembekuan darah semulajadi. Protein ini dirembeskan keluar dari kelenjar liurnya semasa menggigit perumah. Dari beberapa penyelidikan yang pernah dijalankan oleh universiti -universiti tempatan,  protein ini dapat membantu ahli perubatan dalam kajian penyakit-penyakit tertentu oleh kerana hirudin dari lintah tidak toksik berbanding bahan sintetik lain yang lebih mahal.


#petrosains #eww









Posted by Ayu
Learning Specialist, Petrosains






Saturday, 19 April 2014

Food Preservation



Food plays an important role in our lives. Without food, we will not be able to survive. Living in Malaysia is definitely a blessing to us Malaysians. This is because we are able to enjoy different types of foods due to our multi-racial heritage. Thanks to our tropical climate, we are able to produce an abundance of crops and so far our country has not experienced a disastrous food shortage. However, other countries are not as lucky as us. To overcome this problem, humans have invented smart ways to preserve food.
Food preservation is actually the activity of preventing the growth of bacteria or microorganisms from spoiling the food. There are different ways to preserve foods.
The first way is by using heat such as drying and smoking. By introducing sufficient heat, the microorganisms will die since it cannot withstand the high temperature surroundings. Excess water is also removed to slow down the growth of bacteria.

Another way is by curing the food. The food can be cured by either pickling them in vinegar or candying them in sugar. Candying is the process of cooking the food e.g. ginger in sugar till the point of crystallization. Another way is to preserve them in salt such as salted fish or placing them in a heavy sugar syrup solution. Either way, moisture is removed and makes it unsuitable for microorganisms to grow.
Preservatives are also added to mainly increase the food’s shelf life. Canning and bottling involves cooking food and then placing them in sterile cans or jars. The cans or jars are sterilized by boiling them to weaken the growth of bacteria.
Refrigeration and freezing are probably the most popular forms of food preservation in use today. In the case of refrigeration, the idea is to slow bacterial action to a crawl so that it takes food much longer (perhaps a week or two, rather than half a day) to spoil.

One of the advantages of food preservation is mainly that by preserving food, the foods are prevented from being spoiled by the action of enzymes such as ethane and microorganisms. Refrigeration and freezing are probably the most popular forms of food preservation in use today. It allows the food to be stored for a longer period of time. It also increases the availability of certain foods and makes the transportation of foods easier. 

However, the disadvantages of food preservation is that sometimes the nutrients found in fresh foods cannot be found in the foods preserved but this depends on how it is preserved. Besides that, food preserved in jars, cans or etc. cost more due to the packaging. The taste may also differ from fresh foods. Food preservation also requires a long time to process and ready for consumption.


Food preservation has definitely helped us in our daily lives. Not only has it made life easier for those who are busy, but food preservation has helped to overcome a major issues in countries where fresh food is scarce. However, like all things, foods that are preserved are best consumed in moderation.













This blog-post is from Claire Richard, a member of the 2014 Petrosains Science Action Team (SAT) and is one of a series of blog-posts by SAT members to share and communicate science with the general public. 





Wednesday, 16 April 2014

Tanah Liat & Kesan Penyejukannya



Nampak kotor serta menggelikan. Tetapi tidak untuk pesawah yang sentiasa bergelumang dengan tanah liat demi untuk mencari rezeki. Sungguhpun begitu, tahukah anda ia mempunyai banyak kelebihan luar biasa seperti ia mampu memberi kesan penyejukan?Apakah ciri-ciri yang ada pada tanah liat sehingga ia dikatakan sangat unik? Apakah pula proses sains yang terlibat?
Rumah yang beratapkan tanah liat
Tanah liat adalah jenis tanah yang memiliki struktur  liang-liang halus. Pada atap rumah yang diperbuat daripada tanah liat seperti dalam gambar di atas, liang-liang halus berfungsi untuk menyerap haba cahaya matahari  dan sekaligus, menghalang haba tersebut memasuki ruang dalam rumah. Ini akan menyebabkan ruang dalam rumah menjadi kurang panas pada waktu siang berbanding rumah yang mempunyai atap yang diperbuat daripada bahan lain.
Kepingan-kepingan atap diperbuat daripada tanah liat 
Manakala air yang disimpan di dalam labu sayung yang diperbuat daripada tanah liat akan menjadi lebih sejuk daripada suhu di sekeliling disebabkan oleh proses penyejatan yang berlaku pada dinding labu sayung, menurut satu kajian teori yang pernah dijalankan di salah sebuah universiti tempatan. Namun, kadar penyejukan air di dalam labu sayung juga dipengaruhi oleh beberapa faktor lain seperti  kelembapan udara, ketebalan dinding labu dan jenis tanah liat yang digunakan untuk membuatnya.

Labu sayung yang diperbuat daripada tanah liat
Menarik, bukan? Kedua-dua fenomena di atas menerangkan kesan penyejukan yang disebabkan oleh bahan yang digunakan iaitu tanah liat. Proses sains yang terlibat untuk kedua-dua keadaan adalah berbeza, membuktikan bahawa tanah liat memang istimewa!





Posted by Ayu
Learning Specialist, Petrosains






Thursday, 10 April 2014

Let's Balance an Aluminium Can at a 45 Degree Angle



Let’s take a break and watch this cool magic trick that can be done with just a normal aluminium can. It's not even magic, it's actually physics!

video

Want to try this amazing trick yourself? What you need is just an aluminium can, a measuring cup and a small amount of water. Here’s how in 4 easy steps:  

Step 1:
- Get an empty aluminium can.

Step 2:
- Fill a measuring cup to 100ml (or just about half-fill a regular glass with water)

Step 3:
- Pour the water into the can

Step 4:
- Tilt it and balance the aluminium can at a 45 degree angle 


The key to balancing the aluminium can is making sure that the centre of gravity is supported. When the can is empty, the centre of gravity is somewhere in the centre of the can. That means when you tilt it to 45 degree angle, the centre of gravity still remains in the centre of the can but as the can is no longer upright, it will fall over. However, when the can has a little bit of water in it, the centre of gravity will be somewhat in the centre of wherever most of the water is. So when the can with water is at a 45 degree angle, the centre of gravity shifts enough to remain in the ‘centre’ of the tilted can and therefore allowing it to stay in balance.

Try this at home. Test a can with no liquid in it, and then try to figure out how much liquid is needed to balance a tin can at a 45 degree angle. Different types of cans may need different amounts of water in it to make it balance!












This blog-post is from Jiun Hong Lim, a member of the 2014 Petrosains Science Action Team (SAT) and is one of a series of blog-posts by SAT members to share and communicate science with the general public.