Senin, 08 Maret 2010

tembaga & emas...?? logam yang "aneh"....


Setauku ya... sejak jaman SD, SMP sampe SMA yang namanya logam tu cling cling bling,,,, trus agak agak perak gitu dee... tapi kok tembaga sama emas beda ya?
pertamanya sih kupikir emas bukan logam, soalnya warnanya kuning terus dari dulu uda sering ngeliat emas di tiphi,di kuping dan tempat2 yang dianggap indah lainnya....
lhah terus,,, kenapa warnanya bisa mlencong sendiri ya,,, egk kaya logam2 yang lain....
setelah browsing2 akhirnya dapet info juga ternyata tembaga ketika sedikit, melepas warna kilauan merah jambu apabila cahaya yang mencukupi sehingga tembaga berwarna merah, selain itu tembaga memantulkan cahaya merah dan jingga dari spektrum cahaya.Emas berwarna kuning disebabkan oleh frekuensi plasmon emas yang terletak pada julat penglihatan, mengakibatkan warna merah dan kuning dipantulkan sementara warna biru diserap.

ow..ow... jadi begitu,,,,
that's all for today... :)

Sabtu, 05 Desember 2009

polyvinyl chloride...




Two types of polyvinyl chloride (PVC) homopolymer are produced: rigid resins which have considerable strength and hardness; and flexible resins that contain a large proportion of plasticizers to make them soft and stretchable.

Rigid PVC resins are mainly extruded or moulded to make pipe and conduit, fittings, windows, roof tiles, fencing and automobile parts. Flexible PVC finds outlets in film and sheets, wire and cable coating, flooring, shower curtains and synthetic leather products.

Polyvinyl chloride consumption is mostly influenced by the construction industry and so demand correlates closely with economic growth. The global PVC market had been growing around 4%/year with strongest demand growth seen in Asia, in particular China and India. However, global demand collapsed in 2008 due to the economic downturn and destocking throughout the chain. Recovery is expected to be slow in many markets.

Polymerisation is normally performed at 40-70oC with the vinyl chloride monomer (VCM) in a liquid state under pressure in a batch reactor. Suspension polymerisation is the most common PVC process because the resins produced are the most versatile and suitable for a wide range of applications.

Polyvinyl chloride occurs as white, amorphous, odourless powder. PVC is stable under normal temperatures and pressures but above 80oC the resin discolours and evolves hydrogen chloride.


taken from: http://www.icis.com/V2/chemicals/9074317/polyvinyl-chloride.html

accesed: Saturday December 5th 2009 at 09:40 pm

,,oxygen and plants..



Oxygen (O2)is used in large quantities by plants. If you were to analyse a dried plant you would find that about 45% consisted of Oxygen atoms. Just like humans, plants need fresh air and their cells use O2 in the same kind of quantities that ours do. In air conditions with a low concentration of O2, or where the air is poor, plants do not thrive. Those that do manage to eke out an existence remain poor stunted specimens.

The leaves of a plant have easy access to O2. They make it as a natural bi-product of the process of producing plant sugars and breathe it out as waste during the process of photosynthesis.

The roots of the plant do not have the same amount of O2 available to them. They have to work a lot harder to find enough for their needs. Insufficient O2 at the roots will reduce the plants root respiration and result in the shutting down of photosynthesis.

A plant’s growth and its yield are governed by the size and health of its root system. It can only grow to its full potential if the roots have enough O2 for their needs. In plants grown hydroponically this essential ingredient is supplied dissolved in the nutrient solution.

Dissolved Oxygen in the nutrient solution can be measured by a DO meter (dissolved oxygen meter). These are available from all good hydroponics equipment suppliers.

The amount of O2 dissolved in the solution will vary depending on both temperature and pressure. The warmer the water the lower the gaseous content will be. Really cold fresh water has a DO reading of up to 14 ppm or 14mg/litre, while water at 30 degrees centigrade can only hold about 5ppm or 5 mg/l DO.

This DO only amounts to a very small percentage of the roots needs. All water culture systems have to utilise some other form of oxygenation for the roots as well as DO in the nutrient. Root systems that have insufficient O2 available will soon turn brown and become very sick.

We aerate the nutrient in our systems in order to get the best saturation that we can, (from 5ppm to 8ppm) but the main function of this aeration is to kill off the anaerobic bacteria around the roots. Anaerobic bacteria are pathogens that cannot survive in an oxygenated environment; (Anaerobic meaning without air).

Because the DO in the nutrient can only supply about 1% of the roots requirements, the balance must be made up by breathing air. This air is trapped within the soil in conventional gardening and in the growing medium in normal hydroponics systems. This O2 search uses up energy that the plant could better use to produce root growth.

The only type of system where this does not happen is the aeroponics system. The aerated water being sprayed directly onto the roots, allows the plant to take in free Oxygen from the surrounding air, while still keeping the roots moist and supplied with nutrient.

One of the functions of Oxygen is to facilitate the exchange of nutrients and gasses between the plant roots and the surrounding solution. It does this by changing the electrical charges within the water, so allowing the roots to absorb the available nutrients with the least expenditure of energy. For this reason, if no other, the roots need all the Oxygen they can get.


taken from: http://www.hydroponics-gardening-information.com/Oxygen.html On Saturday, December 5th 2009 at 08:52 pm

Rabu, 28 Oktober 2009

Asteroid Jatuh????


Pakar astronomi mengungkapkan bahwa ledakan besar yang terjadi di perairan Teluk Bone pada 8 Oktober 2009 lalu adalah akibat jatuhnya meteorit yang berasal dari asteroid berdiameter sekitar 10 meter ke bumi.

"Ledakan terjadi karena tekanan atmosfer menyebabkan pelepasan energi yang cukup besar, di mana kecepatan jatuh meteorit tersebut sekitar 20,3 km per detik atau 73.080 km per jam," kata pakar astronomi dari Lembaga Penerbangan dan Antariksa Nasional (Lapan) Dr Thomas Djamaluddin di Jakarta, Selasa (27/10).

Sistem pemantau internasional untuk larangan percobaan nuklir dari 11 stasiun, ujarnya, melaporkan telah mendeteksi adanya ledakan besar yang berpusat di sekitar lintang 4,5 LS dan bujur 120 BT, sekitar pukul 11.00 Wita pada 8 Oktober. Analisis ledakan menunjukkan bahwa kekuatan ledakan sekitar 50 kiloton TNT (trinitrotoluena) dan sinyal ledakan tersebut juga mencapai stratosfer yang tingginya lebih dari 20 km.

Kebanyakan asteroid yang jatuh tidak menyebabkan kerusakan di bumi, kecuali diameternya mencapai lebih dari 25 meter. Dikatakan Djamal, berdasarkan perkiraan sebaran meteoroid-asteroid di antariksa dekat bumi, obyek seperti itu punya kemungkinan jatuh di bumi setiap 2 sampai 12 tahun.

Pada Kamis (8/10), warga Kabupaten Bone, Sulawesi Selatan, dikejutkan dengan adanya suara ledakan di mana sejumlah saksi mata sempat melihat benda memancarkan api dan asap di udara.

Namun, informasi yang beredar simpang siur, kebanyakan mengira ledakan itu merupakan ledakan pesawat jet tempur Sukhoi yang sedang melakukan latihan dari markasnya di Skuadron Udara 11 Pangkalan Udara Sultan Hassanuddin, Makassar.

Sedangkan Badan Meteorologi, Klimatologi, dan Geofisika (BMKG) IV Makassar sempat mengaku telah terjadi gempa kecil sebesar 1,9 skala Richter (SR) di permukaan di perbatasan Kabupaten Bone dan Wajo, di mana di wilayah tersebut terdapat Patahan Sa`dang.

Warga lainnya menyebutkan, ledakan yang sempat menimbulkan getaran di darat tersebut disebabkan aksi bom ikan yang dilakukan nelayan setempat, tetapi ada pula warga yang telah menduga bahwa benda tersebut adalah meteorit.

Sabtu, 24 Oktober 2009

Hati-hati 75 Persen Es Kutub Selatan Sudah Hilang


Beberapa ilmuwan Selandia Baru telah memperingatkan bahwa Kutub Selatan mencair lebih cepat daripada perkiraan.

Profesor Peter Barrett dari Antarctic Research Center, Victoria University mengatakan, jumlah es yang hilang mencapai 75 persen sejak 1996, dan bertambah dengan cepat.

Hilangnya gletser di ujung Kutub Selatan mengakibatkan kenaikan permukaan air laut 0,4 Mm per tahun, tambahnya seperti dilaporkan kantor berita Xinhua.

"Hilangnya es global dari Greenland, Antartika dan gletser lain menunjukkan permukaan air laut akan naik antara 80 centimeter dan 2 meter sampai 2100," kata Barett.

Direktur pusat penelitian Profesor Tim Naish, yang memimpin satu tim peneliti yang membor jauh ke dalam batu di Kutub Selatan dan menemukan catatan kuno dari yang terakhir bahwa CO2 atmosfir mencapai tingkatnya sekarang.

Mereka mendapati, 3 juta sampai 5 juta tahun lalu, permukaan air laut cukup hangat untuk mencairkan banyak bagian es Kutub Selatan ketika CO2 atmosfir hanya sedikit lebih tinggi dibandingkan kondisinya hari ini.

Naish mengatakan es di bagian barat Antartika akan mencair sebelum lapisan es yang lebih besar di bagian timur Kutub Selatan karena es itu berada di bawah permukaan air laut dan menghangat bersama dengan air samudra.

Namun, ia mengatakan penelitian tersebut mengangkat pertanyaan yang tak terjawab mengenai berapa banyak CO2 atmosfir perlu naik untuk mencapai temperatur sampai 2 derajat celsius atau lebih.

Kondisi CO2 di atmosfir sekarang berjumlah 387 bagian per juta, naik dari sebanyak 280 bagian per juta pada awal Revolusi Industri.

Kutub Bakal Tak Punya Es


Para peneliti meramalkan, Laut Artik (kutub) akan bebas es pada musim panas dalam satu dekade mendatang. Setelah musim semi berlalu, para peneliti kembali mengukur ketebalan es sepanjang 450 kilometer dengan rute menyeberangi Laut Beaufort. Mereka menemukan sebagian besar es sangat tipis.

Pemimpin ekspedisi dan pakar es lautan dari University of Cambridge, Peter Wadhams, mengatakan, pada musim semi tahun lalu rata-rata ketebalan es hanya 1,8 meter, menandakan usia lapisan itu sekitar satu tahun. Sementara itu, es yang sudah bertahun-tahun sekitar 3 meter.

Tipisnya lapisan tersebut menjadi indikasi penting kondisi memprihatinkan es di Laut Artik. ”Secara sederhana, es tipis itu akan sekejap hilang pada musim es mulai meleleh,” ujarnya. Angin dan arus laut dapat pula memecah es yang tipis itu. Es yang terpecah dan mengapung bebas akan mudah terdorong ke wilayah perairan yang lebih hangat dan mencair. Catlin Arctic Survey dan kelompok konservasi internasional WWF mendukung penemuan tersebut.

Situasi es di Artik tersebut sangat dipengaruhi iklim dan kondisi alam. Kondisi es di Laut Artik kerap pula dikaitkan dengan perubahan iklim dan pemanasan global.

TWILIGHT "new moon" is coming up!!!!




pssst.... sequel twilight yang kedua uda mau maen...... uda egk sabar pengen ngeliat si Edward Cullen.

The second installment of Stephenie Meyers phenomenally successful TWILIGHT series, the romance between mortafeefl and vampire soars to a new level as BELLA SWAN (Kristen Stewart) delves deeper into the mysteries of the supernatural world she yearns to become part of only to find herself in greater peril than ever before.

Following Bellas ill-fated 18th birthday party, EDWARD CULLEN (Robert Pattinson) and his family abandon the town of Forks, Washington, in an effort to protect her from the dangers inherent in their world. As the heartbroken Bella sleepwalks through her senior year of high school, numb and alone, she discovers Edwards image comes to her whenever she puts herself in jeopardy. Her desire to be with him at any cost leads her to take greater and greater risks.

With the help of her childhood friend JACOB BLACK (Taylor Lautner), Bella refurbishes an old motorbike to carry her on her adventures. Bellas frozen heart is gradually thawed by her budding relationship with Jacob, a member of the mysterious Quileute tribe, who has a supernatural secret of his own.

When a chance encounter brings Bella face to face with a former nemesis, only the intervention of a pack of supernaturally large wolves saves her from a grisly fate, and the encounter makes it frighteningly clear that Bella is still in grave danger. In a race against the clock, Bella learns the secret of the Quileutes and Edwards true motivation for leaving her. She also faces the prospect of a potentially deadly reunion with her beloved that is a far cry from the one she'd hoped for. With more of the passion, action and suspense that made TWILIGHT a worldwide phenomenon, THE TWILIGHT SAGA: NEW MOON is a spellbinding follow-up to the box office hit.

Italy 21 October 2009 (Rome Film Festival)
USA 16 November 2009 (Los Angeles, California) (premiere)
Belgium 18 November 2009
France 18 November 2009
Italy 18 November 2009
Spain 18 November 2009
Switzerland 18 November 2009 (French speaking region)
Argentina 19 November 2009
Australia 19 November 2009
Greece 19 November 2009
Hungary 19 November 2009
Netherlands 19 November 2009
New Zealand 19 November 2009
Russia 19 November 2009
Thailand 19 November 2009
Brazil 20 November 2009
Bulgaria 20 November 2009 (Sofia)
Canada 20 November 2009
Cyprus 20 November 2009
Denmark 20 November 2009
Finland 20 November 2009
Mexico 20 November 2009
Norway 20 November 2009
Sweden 20 November 2009
Turkey 20 November 2009
UK 20 November 2009
USA 20 November 2009
Czech Republic 26 November 2009
Germany 26 November 2009
Lebanon 26 November 2009
Portugal 26 November 2009
Slovakia 26 November 2009
Slovenia 26 November 2009
Switzerland 26 November 2009 (German speaking region)
United Arab Emirates 26 November 2009
Estonia 27 November 2009
Iceland 27 November 2009
Latvia 27 November 2009
Lithuania 27 November 2009
Romania 27 November 2009
Venezuela 27 November 2009
Japan 28 November 2009
Singapore 3 December 2009
South Korea 3 December 2009
Taiwan 4 December 2009
Hong Kong 18 December 2009 (Hong Kong International Film Festival)
Egypt 23 December 2009