Gamma


The first gamma ray source to be discovered historically was the radioactive decay process called gamma decay. In this type of decay, an excited nucleus emits a gamma ray almost immediately upon formation (it is now understood that a nuclear isomeric transition, however, can produce inhibited gamma decay with a measurable and much longer half-life).

Paul Villard, a French chemist and physicist, discovered gamma radiation in 1900, while studying radiation emitted from radium. Villard knew that his described radiation was more powerful than previously described types of rays from radium, which included beta rays, first noted as "radioactivity" by Henri Becquerel in 1896, and alpha rays, discovered as a less penetrating form of radiation by Rutherford, in 1899.

However, Villard did not consider naming them as a different fundamental type Villard's radiation was recognized as being of a type fundamentally different from previously-named rays, by Ernest Rutherford.

who in 1903 named Villard's rays "gamma rays" by analogy with the beta and alpha rays that Rutherford had differentiated in 1899. The "rays" emitted by radioactive elements were named in order of their power to penetrate various materials, using the first three letters of the Greek alphabet: alpha rays as the least penetrating, followed by beta rays, followed by gamma rays as the most penetrating.

Rutherford also noted that gamma rays were not deflected (or at least, not easily deflected) by a magnetic field, another property making them unlike alpha and beta rays.

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Gamma rays were first thought to be particles with mass, like alpha and beta rays. Rutherford initially believed they might be extremely fast beta particles, but their failure to be deflected by a magnetic field indicated they had no charge. In 1914, gamma rays were observed to be reflected from crystal surfaces, proving they were electromagnetic radiation.

Rutherford and his coworker Edward Andrade measured the wavelengths of gamma rays from radium, and found that they were similar to X-rays but with shorter wavelengths and (thus) higher frequency. This was eventually recognized as giving them also more energy per photon, as soon as the latter term became generally accepted. A gamma decay was then understood to usually emit a single gamma photon.

Natural sources of gamma rays on Earth include gamma decay from naturally occurring radioisotopes such as potassium-40, and also as a secondary radiation from various atmospheric interactions with cosmic ray particles. Some rare terrestrial natural sources that produce gamma rays that are not of a nuclear origin, are lightning strikes and terrestrial gamma-ray flashes, which produce high energy emissions from natural high-energy voltages.

Gamma rays are produced by a number of astronomical processes in which very high-energy electrons are produced. Such electrons produce secondary gamma rays by the mechanisms of bremsstrahlung, inverse Compton scattering and synchrotron radiation.

A large fraction of such astronomical gamma rays are screened by Earth's atmosphere and must be detected by spacecraft. Notable artificial sources of gamma rays include fission such as occurs in nuclear reactors, and high energy physics experiments, such as neutral pion decay and nuclear fusion.(wikipedia.org)

Cosmic


In the 1920s the term "cosmic rays" was coined by Robert Millikan who made measurements of ionization due to cosmic rays from deep under water to high altitudes and around the globe. Millikan believed that his measurements proved that the primary cosmic rays were gamma rays, i.e., energetic photons.

And he proposed a theory that they were produced in interstellar space as by-products of the fusion of hydrogen atoms into the heavier elements, and that secondary electrons were produced in the atmosphere by Compton scattering of gamma rays. But then, in 1927, J.

Clay found evidence, later confirmed in many experiments, of a variation of cosmic ray intensity with latitude, which indicated that the primary cosmic rays are deflected by the geomagnetic field and must therefore be charged particles, not photons. In 1929, Bothe and Kolhörster discovered charged cosmic-ray particles that could penetrate 4.1 cm of gold.

Charged particles of such high energy could not possibly be produced by photons from Millikan's proposed interstellar fusion process. In 1930, Bruno Rossi predicted a difference between the intensities of cosmic rays arriving from the east and the west that depends upon the charge of the primary particles - the so-called "east-west effect."

Three independent experiments found that the intensity is, in fact, greater from the west, proving that most primaries are positive. During the years from 1930 to 1945, a wide variety of investigations confirmed that the primary cosmic rays are mostly protons, and the secondary radiation produced in the atmosphere is primarily electrons, photons and muons.

physicsworld.com

In 1948, observations with nuclear emulsions carried by balloons to near the top of the atmosphere showed that approximately 10% of the primaries are helium nuclei (alpha particles) and 1% are heavier nuclei of the elements such as carbon, iron, and lead.

During a test of his equipment for measuring the east-west effect, Rossi observed that the rate of near-simultaneous discharges of two widely separated Geiger counters was larger than the expected accidental rate. In his report on the experiment, Rossi wrote "... it seems that once in a while the recording equipment is struck by very extensive showers of particles, which causes coincidences between the counters, even placed at large distances from one another.

In 1937 Pierre Auger, unaware of Rossi's earlier report, detected the same phenomenon and investigated it in some detail. He concluded that high-energy primary cosmic-ray particles interact with air nuclei high in the atmosphere, initiating a cascade of secondary interactions that ultimately yield a shower of electrons, and photons that reach ground level.

Soviet physicist Sergey Vernov was the first to use radiosondes to perform cosmic ray readings with an instrument carried to high altitude by a balloon. On 1 April 1935, he took measurements at heights up to 13.6 kilometers using a pair of Geiger counters in an anti-coincidence circuit to avoid counting secondary ray showers.

Homi J. Bhabha derived an expression for the probability of scattering positrons by electrons, a process now known as Bhabha scattering. His classic paper, jointly with Walter Heitler, published in 1937 described how primary cosmic rays from space interact with the upper atmosphere to produce particles observed at the ground level.

Bhabha and Heitler explained the cosmic ray shower formation by the cascade production of gamma rays and positive and negative electron pairs.(wikipedia.org)

Binatang


Tarantula adalah nama yang diberikan untuk salah satu jenis laba-laba dengan ukuran sangat besar yang umumnya berbulu.Laba-laba ini masuk pada keluarga theraphosidae dan paling tidak ada sekitar 800 spesies yang telah berhasil diidentifikasi.

Sebagian besar spesies tarantula tidak berbahaya untuk manusia, dan beberapa jenis spesies lainnya menjadi terkenal karena diperdagangkan sebagai hewan peliharaaan eksotik.

www.reptilx.com

Tarantula dapat menggigit, karena seperti laba-laba pada umumnya tarantula memiliki taring dan gigitannya dikenal menyakitkan untuk manusia, namun racun dalam gigitannya lebih lemah daripada racun yang terdapat pada lebah madu pada umumnya dan gigitannya diketahui lebih sakit dari sengatan tawon. Nama tarantula berasal dari satu kota di Italia yaitu Taranto

Tarantula hidup di daerah-daerah hangat di seluruh dunia beberapa laba-laba ditemukan hidup dalam sarangnya yang berupa liang yang terdapat di bawah tanah, beberapa lainnya hidup diatas tanah, dan sebagian lain hidup di pohon-pohon.

Mereka juga ditemukan di hutan hujan, padang pasir dan gurun, serta habitat lainnya.Sebaran habitatnya termasuk Amerika Selatan, bagian selatan Amerika Utara, Eropa Selatan, Afrika, bagian selatan Asia, dan Australia.

Tarantula itu adalah hewan dari keluarga arachnida yang cukup berbeda dengan arachnida pada lainnya.

Ukuran tarantula dapat jauh lebih besar daripada laba laba pada umumnya. Kalau laba laba pada umumnya kita lihat memiliki besar sekitar 1 cm, kalau tarantula bisa menembus ukuran 20cm dari rentang kaki ke kakinya.

Dari mitos mitos di kalangan masyarakat yang banyak beredar tentang tarantula adalah mereka dapat membunuh manusia dengan racunnya. Kenyataannya adalah tidak begitu. Riset membuktikan kalau tidak ada orang didunia yang meninggal dunia karena gigitan tarantula,

karena gigitannya hanya mematikan bagi hewan hewan kecil yang menjadi mangsanya seperti serangga dan tikus tikus kecil.

Yang menarik dari tarantula adalah warnanya yang sangat beragam seperti oranye, merah, hitam, putih, biru, pink, bahkan ada yang berwarna ungu. Beberapa jenis diantaranya bahkan sangat jinak dan bisa dipegang oleh manusia.(wikipedia.org)

Tanaman Obat


Secara umum, lidah buaya merupakan satu dari 10 jenis tanaman terlaris di dunia yang mempunyai potensi untuk dikembangkan sebagai tanaman obat dan bahan baku industri.

Berdasarkan hasil penelitian, tanaman ini kaya akan kandungan zat-zat seperti enzim, asam amino, mineral, vitamin, polisakarida dan komponen lain yang sangat bermanfaat bagi kesehatan.

Selain itu, menurut Wahyono E dan Kusnandar (2002), lidah buaya berkhasiat sebagai anti inflamasi, anti jamur, anti bakteri dan membantu proses regenerasi sel.

majalahkesehatan.com

Di samping menurunkan kadar gula dalam darah bagi penderita diabetes, mengontrol tekanan darah, menstimulasi kekebalan tubuh terhadap serangan penyakit kanker, serta dapat digunakan sebagai nutrisi pendukung penyakit kanker, penderita HIV/AIDS.

Salah satu zat yang terkandung dalam lidah buaya adalah aloe emodin, sebuah senyawa organik dari golongan antrokuinon yang mengaktivasi jenjang sinyal insulin seperti pencerap insulin-beta dan -substrat1, fosfatidil inositol-3 kinase dan meningkatkan laju sintesis glikogen dengan menghambat glikogen sintase kinase 3beta


sehingga sangat berguna untuk mengurangi rasio gula darah.
Di negara-negara Amerika, Australia, dan Eropa, saat ini lidah buaya juga telah dimanfaatkan sebagai bahan baku industri makanan dan minuman kesehatan.

Lidah buaya mengandung banyak vitamin dan mineral yang efektif untuk mengobati rambut rontok. Campur ekstrak lidah buaya dengan shampo dan oleskan pada rambut Anda.

Penipisan rambut membuat Anda jadi botak? Anda dapat meningkatkan pertumbuhan rambut dengan mengoleskan gel atau jus lidah buaya pada kulit kepala Anda secara teratur. Biarkan 10 menit dan bilas dengan shampo.

Jika Anda menderita ketombe, kulit kepala kering dan gatal, segera gunakan gel atau jus lidah buaya untuk mengobati ketombe secara alami. Oleskan ekstrak lidah buaya pada kulit kepala dan biarkan selama 40-60 menit untuk menyingkirkan ketombe.(wikipedia.org)

Teknolog


Pernahkah terbayangkan, memutar video high definition (HD) dari notebook atau PC ke layar TV tanpa menggunakan kabel? Berkat alat anyar yang baru diperkanenalkan D-Link, hal tersebut bisa dilakukan.

Namanya D-Link DH-131 Wireless Display (WiDi), bentuk dan fisiknya mirip perangkat akses point nirkabel yang sering dijadikan hotspot, hanya saja yang ini sedikit lebih mungil.


D-Link

Di belakangnya ada port High Definition Multimedia Interface (HDMI) yang bisa dihubungkan ke layar High Definition Television (HDTV) alias televisi berdefinisi tinggi.

Nah, PC atau notebook yang punya konten HD kemudian terhubung ke D-Link DHD-131 ini menggunakan jaringan nikabel.
 
Menurut klaim D-Link, DHD-131 bisa mengalirkan video beresolusi 1080p (Full HD) pada 30 frame per detik lewat jaringan nirkabel menggunakan kompresi video H.264. Supaya aman D-Link tidak ketinggalan memasukkan standar pengamanan  WPA/WPA2 di jalur nirkabel DHD-131.

“Inovasi pertama kami ini berdasarkan pada platform WiDi, D-Link DHD-131 membuat streaming dan melihat konten-konten dengan definisi tinggi menjadi lebih mudah dan nyaman,” kata Desmond Toh, Direktur Pemasaran dari D-Link International Pte Ltd.

Sayang belum ada informasi harga jual D-Link DHD-131 di Indonesia beserta tanggal resmi ketersediaannya.(beritateknologi.com)

Jejaring Sosial


Kabar mengenai langkah Twitter untuk melakukan IPO (initial public offering) sedikit demi sedikit mulai terjawab. Perusahaan jejaring sosial yang berbasis di San Francisco tersebut pun baru saja mengumumkan harga awal saham miliknya, yakni sebesar 26 USD per lembar.

bikeleague.org

Total Twitter akan menjual sebanyak 70 juta lembar saham. Pihak Twitter pun akan menunjuk beberapa perusahaan seperti Goldman Sachs, JP Morgan, Morgan Stanley, BofA Merril Lynch serta Deutsche Bank sebagai bookrunner. Sementara itu Code Advisors dan Allen & Company akan bertindak sebagai co-manager.
 
Harga saham awal Twitter tersebut pun lebih rendah jika dibandingkan yang telah dilakukan oleh Facebook. Pada saat melakukan IPO, Facebook menawarkan sahamnya dengan harga sebesar 38 USD per lembar.

Dan seperti halnya yang terjadi pada IPO Facebook, penjualan saham awal Twitter tersebut pun nantinya diperkirakan bakal menarik banyak perhatian. Dan IPO tersebut akan mulai dilaksanakan oleh Twitter pada 7 November waktu Amerika di New York Stock Exchange.(beritateknologi.com)