Minggu, 17 November 2013

New aluminum alloy stores hydrogen


This is a schematic of the hydrogenation reaction process of the newly developed hydride Al2CuHx. -  H. Saitoh /JAEA
This is a schematic of the hydrogenation reaction process of the newly developed hydride Al2CuHx. - H. Saitoh /JAEA
We use aluminum to make planes lightweight, store sodas in recyclable containers, keep the walls of our homes energy efficient and ensure that the Thanksgiving turkey is cooked to perfection. Now, thanks to a group of Japanese researchers, there may soon be a new application for the versatile metal: hydrogen storage for fuel cells.
Lightweight interstitial hydrides -- compounds in which hydrogen atoms occupy the interstices (spaces) between metal atoms -- have been proposed as a safe and efficient means for storing hydrogen for fuel cell vehicles. Hydrides using magnesium, sodium and boron have been manufactured, but so far, none have proven practical as a hydrogen repository. An aluminum-based alloy hydride offers a more viable candidate because it has the desired traits of light weight, no toxicity to plants and animals, and absence of volatile gas products except for hydrogen. Until now, however, only complex aluminum hydrides -- unsuitable for use as a hydrogen storage system -- have been created.
In a recent paper in the AIP Publishing journal APL Materials, a joint research group with members from the Japan Atomic Energy Agency (Hyogo, Japan) and Tohoku University (Sendai, Japan) announced that it had achieved the long-sought goal of a simple-structured, aluminum-based interstitial alloy. Their compound, Al2CuHx, was synthesized by hydrogenating Al2Cu at an extreme pressure of 10 gigapascals (1.5 million pounds per square inch) and a high temperature of 800 degrees Celsius (1,500 degrees Fahrenheit).
The researchers characterized the conditions of the hydrogenation reaction using in-situ synchrotron radiation X-ray diffraction measurement, while the crystal and electron structures of the compound formed were studied with powder X-ray diffraction measurement and first-principle calculations, respectively. Together, these examinations confirmed the first-ever formation of an interstitial hydride of an aluminum-based alloy.

3-dimensional carbon goes metallic



This shows 3-D metallic carbon with interlocking hexagons. -  Figure courtesy of Qian Wang, Ph.D.
This shows 3-D metallic carbon with interlocking hexagons. - Figure courtesy of Qian Wang, Ph.D.
A theoretical, three-dimensional (3D) form of carbon that is metallic under ambient temperature and pressure has been discovered by an international research team.
The findings, which may significantly advance carbon science, are published online this week in the Early Edition of the Proceedings of the National Academy of Sciences.
Carbon science is a field of intense research. Not only does carbon form the chemical basis of life, but it has rich chemistry and physics, making it a target of interest to material scientists. From graphite to diamond to Buckminster fullerenes, nanotubes and graphene, carbon can display in a range of structures.
But the search for a stable three-dimensional form of carbon that is metallic under ambient conditions, including temperature and pressure, has remained an ongoing challenge for scientists in the field.
Researchers from Peking University, Virginia Commonwealth University and Shanghai Institute of Technical Physics employed state-of-the-art theoretical methods to show that it is possible to manipulate carbon to form a three-dimensional metallic phase with interlocking hexagons.
"The interlocking of hexagons provides two unique features - hexagonal arrangement introduces metallic character, and the interlocking form with tetrahedral bonding guarantees stability," said co-lead investigator Puru Jena, Ph.D., distinguished professor of physics in the VCU College of Humanities and Sciences.

Chemical Weapons

Chemical Weapons

1. The provisions of this Article and the detailed procedures for its implementation shall apply to all chemical weapons owned or possessed by a State Party, or that are located in any place under its jurisdiction or control, except old chemical weapons and abandoned chemical weapons to which Part IV (B) of the Verification Annex applies.
2. Detailed procedures for the implementation of this Article are set forth in the Verification Annex.
3. All locations at which chemical weapons specified in paragraph 1 are stored or destroyed shall be subject to systematic verification through on site inspection and monitoring with on site instruments, in accordance with Part IV (A) of the Verification Annex.
4. Each State Party shall, immediately after the declaration under Article III,
paragraph 1 (a), has been submitted, provide access to chemical weapons specified in paragraph 1 for the purpose of systematic verification of the declaration through on site inspection.  Thereafter, each State Party shall not remove any of these chemical weapons, except to a chemical weapons destruction facility.  It shall provide access to such chemical weapons, for the purpose of systematic on site verification.
5. Each State Party shall provide access to any chemical weapons destruction facilities and their storage areas, that it owns or possesses, or that are located in any place under its jurisdiction or control, for the purpose of systematic verification through on site inspection and monitoring with on site instruments.
6. Each State Party shall destroy all chemical weapons specified in paragraph 1 pursuant to the Verification Annex and in accordance with the agreed rate and sequence of destruction (hereinafter referred to as "order of destruction").  Such destruction shall begin not later than two years after this Convention enters into force for it and shall finish not later than 10 years after entry into force of this Convention.  A State Party is not precluded from destroying such chemical weapons at a faster rate.
7. Each State Party shall:
          (a) Submit detailed plans for the destruction of chemical weapons specified in paragraph 1 not later than 60 days before each annual destruction period begins, in accordance with Part IV (A), paragraph 29, of the Verification Annex; the detailed plans shall encompass all stocks to be destroyed during the next annual destruction period;
          (b) Submit declarations annually regarding the implementation of its plans for destruction of chemical weapons specified in paragraph 1, not later than 60 days after the end of each annual destruction period; and
          (c) Certify, not later than 30 days after the destruction process has been completed, that all chemical weapons specified in paragraph 1 have been destroyed.
8. If a State ratifies or accedes to this Convention after the 10 year period for destruction set forth in paragraph 6, it shall destroy chemical weapons specified in paragraph 1 as soon as possible.  The order of destruction and procedures for stringent verification for such a State Party shall be determined by the Executive Council.
9. Any chemical weapons discovered by a State Party after the initial declaration of chemical weapons shall be reported, secured and destroyed in accordance with Part IV (A) of the Verification Annex.
10. Each State Party, during transportation, sampling, storage and destruction of chemical weapons, shall assign the highest priority to ensuring the safety of people and to protecting the environment.  Each State Party shall transport, sample, store and destroy chemical weapons in accordance with its national standards for safety and emissions.
11. Any State Party which has on its territory chemical weapons that are owned or possessed by another State, or that are located in any place under the jurisdiction or control of another State, shall make the fullest efforts to ensure that these chemical weapons are removed from its territory not later than one year after this Convention enters into force for it.  If they are not removed within one year, the State Party may request the Organization and other States Parties to provide assistance in the destruction of these chemical weapons.
12. Each State Party undertakes to cooperate with other States Parties that request information or assistance on a bilateral basis or through the Technical Secretariat regarding methods and technologies for the safe and efficient destruction of chemical weapons.
13. In carrying out verification activities pursuant to this Article and Part IV (A) of the Verification Annex, the Organization shall consider measures to avoid unnecessary duplication of bilateral or multilateral agreements on verification of chemical weapons storage and their destruction among States Parties.
To this end, the Executive Council shall decide to limit verification to measures complementary to those undertaken pursuant to such a bilateral or multilateral agreement, if it considers that:
          (a) Verification provisions of such an agreement are consistent with the verification provisions of this Article and Part IV (A) of the Verification Annex;
          (b) Implementation of such an agreement provides for sufficient assurance of compliance with the relevant provisions of this Convention; and
          (c) Parties to the bilateral or multilateral agreement keep the Organization fully informed about their verification activities.
14. If the Executive Council takes a decision pursuant to paragraph 13, the Organization shall have the right to monitor the implementation of the bilateral or multilateral agreement.
15. Nothing in paragraphs 13 and 14 shall affect the obligation of a State Party to provide declarations pursuant to Article III, this Article and Part IV (A) of the Verification Annex.
16. Each State Party shall meet the costs of destruction of chemical weapons it is obliged to destroy.  It shall also meet the costs of verification of storage and destruction of these chemical weapons unless the Executive Council decides otherwise.  If the Executive Council decides to limit verification measures of the Organization pursuant to paragraph 13, the costs of complementary verification and monitoring by the Organization shall be paid in accordance with the United Nations scale of assessment, as specified in Article VIII, paragraph 7.
17. The provisions of this Article and the relevant provisions of Part IV of the Verification Annex shall not, at the discretion of a State Party, apply to chemical weapons buried on its territory before 1 January 1977 and which remain buried, or which had been dumped at sea before 1 January 1985.

The periodic table: how elements get their names


Periodic table of elements
Most people could name many of the elements, but how many of us know how they got those names?
Each of the 115 known chemical elements was discovered over the last few thousand years, from before recorded history began to the nuclear laboratories of the 21st century.

British scientists and the elements

Humphry Davy experimenting
  • Humphry Davy discovered nine elements using electrolysis - the splitting up of compounds into elements by applying electricity.
  • William Ramsay discovered a new group of unreactive elements using spectroscopy, now called the noble gases.
  • William Crookes identified helium for the first time, and also discovered thallium.
Their chosen names were influenced by an ever changing mix of language, culture and our understanding of chemistry.
So how did they get these names? And why do they end in -ium?
Ancient Elements Several elements' names have Anglo-Saxon language origins, including gold, iron, copper and silver.
These metals were known long before they got these names, however. Gold can be found in its pure form in nature and although iron is usually found in ores which require smelting, the earliest known iron artefacts, from 3500 BCE, derive from purer metal from meteorites.
The Latin names of these elements are commemorated in their atomic symbols, Au (aurum) for gold and Fe (ferrum) for iron.
The Romans began the practise of element names ending in "-um," with Victorian scientists continuing the trend.
Piece of meteoric iron Meteoric iron was used by humans before smelting of iron ores was invented.
Element of uncertainty Since 1947, the International Union of Pure and Applied Chemistry (IUPAC) has had the responsibility for approving elements' names, and deciding the single internationally recognised symbol for each element.
Before this, there were multiple historical occasions of elements being given several names, usually due to simultaneous discovery or uncertainty over a discovery.
The name of element 41 was not agreed for 150 years. It was called columbium in America and niobium in Europe until IUPAC finally decided the official name would be niobium in 1949.
Dr Fabienne Meyers, Associate Director of IUPAC, explains the current naming process: To start with, "the discoverers are invited to propose a name and a symbol."
"For linguistic consistency, the recommended practice is that all new elements should end in '-ium'," she adds.

“Start Quote

The sake of naming an element is essentially to avoid confusion.”
Dr Fabienne Meyers Associate Direcor, IUPAC
"Since the sake of naming an element is essentially to avoid confusion, it is important to ensure that the proposed name is unique and has not been used earlier even unofficially or temporarily for a different element."
"After examination and acceptance by the division - which includes a public review period of five months - the name and symbol are then submitted to the IUPAC Council for approval."
The name is then published in the scientific journal Pure and Applied Chemistry.
Actinium to zirconium A common source of names both now and historically, over a quarter of the elements are named after a place, often where they were discovered or synthesised.
These places range in size from continents (europium) and countries (americium, francium, polonium) to the the Scottish village Strontian (strontium).
Because of the great wealth of discoveries made there, four elements are named after the Swedish mining village, Ytterby (ytterbium, yttrium, erbium and terbium).
There is just one element that wasn't first discovered on Earth, and it too is named after its place of the discovery - helium, from the Greek word for Sun, helios.
Myth and legend
Photograph of Dmitri Mendeleev Dmitri Mendeleev published the periodic table in its modern form.
About a dozen elements take their name directly from legends, including titanium, arsenic and tantalum.
Nickel and cobalt are named after 'devil' and 'kobold', from the Germanic folk belief that malign creatures snuck into mines to replace valuable and similar-looking copper and silver ores with these less valuable ones.
In 1949 the artificial element Promethium was named after Prometheus, the man in Greek legend punished with eternal torture for stealing fire from the gods, as a reference to the great difficulty and sacrifice needed to synthesise new elements.
Eponymous elements Modestly, no discoverer has ever named an element after him or herself, but several scientists have been honoured by having elements named after them. These include curium, einsteinium and fermium.
Seaborgium, named after American chemist Glenn Seaborg, was the first element to be named after a living scientist.
There is also mendelevium, named after Dmitri Mendeleev, the Russian scientist who established the first periodic table in 1869, and fitted the known elements into their places in the table based on their properties.
Elemental techniques
Glass vial of green chlorine gas Sample of chlorine created by Humphry Davy in 1810. It is named after the Greek word for green.
Fifty elements were discovered in the 19th Century, the greatest number of any century. By comparison, twenty nine elements were discovered in the 20th Century, and five new ones have been synthesised so far in the 21st.
Frank James, Professor of the History of Science at The Royal Institution in London, where several elements were discovered, says that the contribution of British scientists was very important.
"Using electro-chemical methods, Humphry Davy either isolated or demonstrated the elemental nature of a total of nine chemical elements naming most of them in the process, such as sodium, potassium and chlorine."
British scientist William Ramsay used a powerful new technique, spectroscopy, to discover the noble gases, a group of elements which had evaded discovery due to their lack of reactivity. He used Greek words to name neon (new), xenon (stranger), krypton (hidden), and argon (inactive).
Colours and sense Colours are a name source for nine elements. Each element can be identified by the colours it emits using spectroscopy, and several elements are named after the brightest colour they emit, including indium and rubidium.

Spectroscopy

The unique emission spectrum of helium
Each element can be made to emit a unique spectrum of light which identifies it like a fingerprint. Helium's emission spectrum is shown above.
WATCH: Brian Cox explains how the colour of stars reveals what they are made of
WATCH: Brian Cox explains how the chemical elements are created within stars
Visible traits are a major source of names, but the other senses are represented too: osmium and bromine are named for their smell, and aluminium is named after the Latin word for the bitter tasting chemical in which it was first discovered, alum.
Ununpentium onwards The newest element to be experimentally confirmed, element 115, will be called ununpentium until an official name is decided, and 114 (Flerovium) and 116 (Livermorium) were named in 2012.
IUPAC's Dr Meyers explains that although all recent elements have been named after people and places, "a mythological concept or character, a mineral or a property of the element could also be used as the root for an acceptable name."
And with no shortage of eminent scientists and important centres of science as inspiration, new names will always retain an element of surprise.

Bahan Lain yang Berbahaya dalam Pabrik

Di samping pada bahan pencemar yang lepas ke udara terdapat pula bahan tertentu yang tersimpan ataupun masih dalam proses di pabrik. Bahan ini karena sifat fisis dan kimianya cukup berbahaya bagi lingkungan apabila terlepas dengan sengaja ataupun tidak sengaja. Sifat racun suatu bahan belum tentu sama dengan sifat bahaya. Bahan yang bersifat racun 591 belum tentu men imbulkan/merupakan bahaya apabila bahan tersebut digunakan secara tepat.
Sifat racun menunjukkan efek biologis atau kemampuan untuk melukai tubuh, sedang sifat bahaya menunjukkan kemungkinan kerugian. Bahan semacam ini banyak digunakan sebagai bahan penolong ataupun bahan utama pabrik kimia. Juga banyak diperoleh sebagai hasil jadi atau sampingan.
Tingkat bahaya yang ditimbulkan sebagai racun sangat membahayakan bagi manusia karena menimbulkan bermacam-macam gangguan seperti: merusakkan kulit, menyulitkan pernafasan, akut maupun kronis, bahkan dapat mematikan. Di samping itu mempunyai daya ledak, mudah terbakar, mudah menyala, sehingga pengelolaannya harus dilakukan dengan sangat herhati-hati.
Bensena, siklo hexanol, asam sulfat, amonium hidroksida,amonium sulfat, amonium nitrat, hidrogen karbon dioksida,belerang dioksida dan lain-lain yang terdiri dari 90 macam bahan,telah diklasifikasikan sebagabahan tersebut ialah tentang penyimpanan, pengolahan, pengemasan dan transportasi.
Oleh sebab itu pengawasan dan pengamanan terhadap bahan ini harus ditingkatkan dari waktu ke waktu menyangkut sifat fisis dankimia. Besarnya resiko kerusakan lingkungan akibat bahan tersebut telah banyak terbukti seperti tragedi Chernobyl di Uni Soviet ataupun Bhopal di India.Kerusakan yang ditimbulkannya selain mengancam kehidupan manusia juga akan mengancam biota lainnya baik dalam jangka panjang maupun pendek.
Kehadiran bahan beracun dan berbahaya sebagai limbah seperti mata rantai yang tak berujung. Bila kita bertolak dari sudut pengadaan akan jelas bahwa kebutuhan bahan tersebut selalu harus terpenuhi. Pengadaan dilakukan dari pabrik (produksi) maupun import. Bahan ini dalam bentuknya sesuai dengan sifatnya harus tersimpan secara baik. Lokasi penyimpanan dan wadahnya juga harus memenuhi kriteria tertentu sesuai dengan klasifikasi yang ditetapkan.
Barang-barang tersebut bila hendak dipindahkan/diangkut untuk kebutuhan proses industri membutuhkan angkutan tersendiri, mungkin dibutuhkan desain khusus alat pengangkut sampai kepada proses, sehingga menjadi barang jadi atau setengah jadi untuk kemudian dikonsumsi oleh industri hilir atau konsumen langsung. Oleh pihak industri maupun konsumen untuk sebagian terbuang sebagai limbah. Sebagai limbah yang ekonomis dapat didaur ulang dan sebagai limbah nonekonomis akan dibuang melalui proses pangolahan.
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Bila dilihat dalam mata rantai tersebut, setiap titik akan menimbulkan peluang untuk mencemarkan dan atau merusakkan lingkungan. Kriteria beracun dan berbahaya akan memenuhi setiap mata rantai tersebut. Berbahaya dan beracun yang dimaksudkan karena dapat mematikan seketika atau pun beberapa lama, dapat secara biologis, dapat berakumulasi dalam lingkungan dan terakhir tidak bisa terdegradasi.
Ditinjau dari sudut pengawasan dan pengamanan bahan ini pengelolaannya harus dilaksanakan mulai dari pengadaan sampai kepada distribusi. Mengingat seringnya terjadi kecelakaan yang ditimbulkan bahan beracun dan berbahaya maka setiap pengusaha dianjurkan untuk membuat label setiap jenis bahan tersebut. Label itu menunjukkan jenis bahan, sifat kimia maupun Pengadaan Pengangkutan
Penyimpanan Limbah ekonomis.
fisikanya sehingga setiap orang dapat melihat dan membaca. Dari penjelasan. dalam label mungkin juga terdapat beberapa usaha pencegahan andaikata terjadi hal-hal yang tidak sesuai menurut prosedur.

Bahan kimia berbahaya dalam kosmetik


Bahan kimia berbahaya dalam kosmetik

Bahan kimia berbahaya dalam kosmetik

Selain beberapa bahan kimia diatas, ada beberapa bahan kimia lain yang lebih terkenal yang sering digunakan dalam kosmetik. Berikut bahan kimia berbahaya dalam kosmetik yang sering ditemukan :

Merkuri atau Air Raksa
Air raksa adalah bahan yang biasanya digunakan untuk mengawetkan hewan yang sudah mati seperti harimau, anjing, macan tutul, dan sebagainya. Merkuri atau air raksa ini tergolong ke dalam kategori logam berat yang berbahaya yang dalam konsentrasi yang kecil sekalipun sudah merupakan zat racun.

Penggunaan merkuri dalam kosmetik akan menyebabkan berbagai macam masalah seperti perubahan pada warna kulit,  iritasi kulit, alergi, kerusakan pada otak, ginjal, dan juga gangguan perkembangan janin bahkan paparan jangka pendek dalam dosis yang tinggi dan bisa menyebabkan muntah-muntah. Selain itu, yang lebih berbahaya ialah bahwa merkuri atau air raksa ini merupakan zat karsinogenik atau zat yang bisa menyebabkan kanker pada manusia.

Asam Retinoat
Asam retinoat  ini cukup beresiko tinggi apabila ikut dalam campuran bahan untuk kosmetika. Asam retinoat bisa menyebabkan rasa terbakar pada kulit, kulit kering, dan juga cacat pada rahim (teratogenik).

Hidrokinon
Hidrokinon  termasuk salah satu obat keras yang patut diminimalisir bahkan dihindari penggunaannya. Bahaya pemakaian obat keras tanpa pengawasan dokter bisa menyebabkan iritasi kulit yang merah dan rasa terbakar serta bercak-bercak hitam.

Setelah tahu berbagai bahan kimia berbahaya dalam kosmetik yang bisa menyebabkan alergi dan kanker. Semestinya harus lebih berhati-hati dalam memilih kosmetik agar tidak berakifat negatif bagi pengguna.

Kandungan Kimia Dan Manfaat Daun Sirsak


manfaat dan khasiat yang terkandung dalam daun sirsak untuk kesehatan tubuh
Kandungan kimia dan manfaat daun sirsak :: Setelah sebelumnya diulas tentang kandungan gizi dan khasiat buah sirsak, artikel kali ini akan mengulas tentang kandungan senyawa kimia dalam daun sirsak serta manfaatnya bagi kesehatan tubuh.
Tidak kalah dengan buah sirsak, Daun sirsak juga memiliki khasiat hampir sama untuk kesehatan tubuh. Khasiat ini  tidak terlepas dari beberapa senyawa kimia yang terkandung dalam daun sirsak

Kandungan kimia daun sirsak.

Daun sirsak mengandung tanin, alkaloid, dan sejumlah kandungan kimia lainnya seperti acetogenins, annocatacin, annocatalin, annohexocin, annonacin, annomuricin, anomurine, anonol, gentisic acid caclourine, linoleic acid, gigantetronin dan muricapentocin. Kandungan senyawa kimia tersebut merupakan senyawa yg dapat memberikan manfaat untuk tubuh, baik sebagai obat ataupun meningkatkan sistem kekebalan tubuh.

Manfaat daun sirsak bagi kesehatan

Daun sirsak digunakan sebagai obat tradisional untuk menyembuhkan beberapa macam penyakit. Cara penggunaannya bisa secara sederhana yaitu merebus daun sirsak atau secara modern dengan mengambil ekstak dari daun. Tubuh akan mendapatkan manfaat dari air rebusan / ektrak daun sirsak ini bila dikonsumsi secara rutin dan teratur.
Beberapa manfaat daun sirsak bisa kita dapatkan untuk kesehatan tubuh antara lain :
  1. Menghambat mutasi gen, pertumbuhan bakteri, perkembangan virus, perkembangan parasit, dan pertumbuhan tumor.
  2. Menurunkan kadar gula, demam, dan tekanan darah tinggi.
  3. Membantu menguatkan syaraf, meningkatkan produksi asi pada ibu hamil, melebarkan pembuluh darah, menyehatkan jantung, meredakan nyeri, mengurangi stess, serta merileksasi otot.
  4. Menguatkan pencernaan dan meningkatkan nafsu makan.
  5. Dapat menekan peradangan.
  6. Membunuh cacing parasit dan sebagai anti kejang

Manfaat daun sirsak untuk kanker

Daun sirsak banyak dipercaya bisa menyembuhkan kanker. Dalam daun sirsak banyak terkandung zat aktif dimana salah satunya bersifat antioksidan yg mampu menangkal radikal bebas penyebab kanker. Daun sirsak juga dapat menaikkan sistem imun tubuh serta mengurangi efek yang ditimbulkan dari penyakit kanker pada tubuh.
Sampai saat ini, sebenarnya riset tentang khasiat daun sirsak hanya baru sampai uji pra klinik, dan belum secara formal di ujicobakan pada manusia. Dengan melakukan tes uji kepada manusia, dapat ditentukan siapa yang boleh dan tidak mengkonsumsi.
Dalam prakteknya, satu tanaman obat bisa menyembuhkan penyakit pada pengguna yang satu tapi justru dapat menimbulkan penyakit pada pengguna lainnya.
Demikian ulasan mengenai sejumlah kandungan kimia dan manfaat daun sirsak sebagai tanaman obat tradisional. Smoga artikel ini bisa memberikan manfaat.