M. Nakayama, S. Toyohisa, A. Fukushima teşekkür ediyoruz ve Y. Ishida için deneysel kurulumu için destekler. JSP'ler Grantin yardımından için bilimsel araştırma (B) aracılığıyla Proje No 26287061 ve Proje No ile genç bilim adamları (B) için fon minnetle anıyoruz 15K 17675. Bu eser de (yenilikçi alan "topolojik malzeme bilimi," vermek No. 16 H 00979) Japonya MEXT ve JSP'ler KAKENHI (Grant No. 16 H 02209) tarafından desteklenmiştir

1. örnek Mount ve yükleme
<ol><li>Tek-kristal örnekleri bı2Se313 yaklaşık bir 1 × 1 × 0,5 mm boyutunda kesme örnek tutucusu örneğe yapıştırmak için3 ve kullanım gümüş tabanlı epoksi.</li>
	<li>İskoç teyibini örnek yüzeyinde yapıştırın. Not: İskoç teyibini atomik temiz bir yüzey elde etmek için ultrahigh vakum (UHV) odası örnekte ayırmak için kullanılır.</li>
	<li>İçine yük kilit Dergisi örnek örnek yükleyin ve yük kilidi basınç 1 × 10-5 PA daha düşük olana pompa başlatın</li>
</ol>2. örnek fizyon
<ol><li>UHV Vana UHV hazırlık odası arasındaki yük kilidi açın.</li>
	<li>Örnek dergi yük kilit odasına bağlı doğrusal/döner feedthrough kullanarak yük kaya Hazırlık odasına taşıyın.</li>
	<li>Hazırlık odasına bağlı transfer çubuk tarafından dergi örnekten örnek almak.</li>
	<li>Örnek Dergisi yük kilide koy ve UHV Vanayı kapat.</li>
	<li>Hazırlık odası baskısı 5 × 10-7 PA tamamlanana kadar bekleyin</li>
	<li>Hazırlık odasında sallantı stick kullanarak İskoç teyibini soyma ve örnek UHV koşul altında ayırmak.</li>
</ol>3. örnek Transfer için ölçüm konumu
<ol><li>Örnek UHV ölçüm odasına aktarmak ve ölçüm odası ile donatılmış tornavida tarafından ana gonio aşamasına örnek düzeltmek.</li>
	<li>Gonio aşamalı ölçüm konuma taşımak ve mikrometre sahne tam olarak örnek konum Spektrometre odak üzerine taşımak için kullanın.</li>
</ol>4. 7eV-lazer Kur
<ol><li>Nd:YVO4 lazer açın. Not: Lazer yüksek tekrarlama oranı 120 MHz ile 355 nm lazer ışık üretir.</li>
	<li>Lazer ışını çekim açın ve lazer KBBF kristal ve 177 ikinci harmonik dalgası üzerinden geçer emin olun nm (6.994 eV) oluşturulur.</li>
	<li>7 eV-lazer gücü 355 nm lazer ile değişken zayıflatıcı gücünü değiştirerek optimize.</li>
</ol>5. ARPES veri toplama
<ol><li>Analyzer denetim yazılımı masaüstü bilgisayarda açın. Not: "Bir elektron saptırıcı ile kontrol ScientaOmicron analyzer için genel bir program olan SES yazılım" kullanın.</li>
	<li>Kurulum sırası menüsünden aşağıda seçin (Şekil 2, adım i.2-1) bar.</li>
	<li>ARPES yapılandırma (Şekil 3, adım ı.3-1) ve ARPES eşleme listesinde (Şekil 3, adım ı.3-2) photoelectron yansıtıcı yüzey eşleştirmeyle Fermi gerçekleştirmek için seçin.</li>
	<li>(Şekil 3, adım ı.3-3) Düzenle ' yi tıklatın ve Fermi yüzey eşleme-12 ° adım boyu 0.5 ° (Şekil 3, adım ı.3-4) ile bir emisyon açının θy 12 ° arasında değişen yapılandırın. Not: Hemisferik analyzer bir elektron saptırıcı ile bize örnek rotasyonlar olmadan Fermi yüzey eşlemek sağlar.</li>
	<li>(Şekil 2, adım i.2-3) Çalıştır ' ı tıklatın.</li>
</ol>6. SARPES veri toplama
<ol><li>El ile makine Kurulum Çözümleyicisi giriş yarık ve diyafram boyutu (resim 1) de dahil olmak üzere SARPES ölçüm için değiştirin.</li>
	<li>Kurulum sırası menüsünden aşağıda seçin (Şekil 2, adım i.2-2) bar.</li>
	<li>(Şekil 4, adım ı.4'te-1) yapılandırma Spin ve Normal listesinde (Şekil 4, adım ı.4'te-2) seçip Tamam (Şekil 4, adım ı.4'te-3)'ı tıklatın.</li>
	<li>DA30 (Şekil 5adım i.5-1) menü çubuğu ve Denetim tetaseçin... (DA30 açı (çapx, θy) yapılandırması için ayar panelini açmak içinŞekil 5adım i.5-2).</li>
	<li>Emisyon açı (çapx, θy) seçin SARPES spectra (Şekil 5adım i.5-3) almak (-6 °, 0 °) =.</li>
	<li>Manyetik alan iki kutuplu kondansatör banka VLEED hedef belirli eksen boyunca olumlu yönde manyetize kontrol ederek uygulamak (α: x, yveya z). Not: sistemimiz içinde buyurmak-e sevketmek ile [Şekil 6 (bir)] Bu işlem yapılabilir.</li>
	<li>Yoğunluk spektrum (Şekil 2, adım i.2-3) almak için Çalıştır ' ı tıklatın.</li>
	<li>Manyetik alan VLEED hedef α boyunca negatif yönde manyetize ve tarama yoğunluğu spektrum almaya başlamak için geçerli.</li>
	<li>Spin-polarizasyon ve spin çözüldü spectra hesaplayın.</li>
</ol>7. ışık polarizasyon bağımlılık taraması
<ol><li>λ/2-waveplate tam 7 eV-lazer ışık kutuplaşma ayarlamak için adım motor tarafından kontrollü açısını değiştirmek. Not: bizim sistemi, komut istemi [Şekil 6 (b)] ile bu işlem yapılabilir.</li>
	<li>X, y ve z eksenleri için spin çözüldü spectra al.</li>
	<li>Spin çözüldü spectra 0 ° yarım waveplate açıdan adım boyu 3 ° ile 102 ° değişen ışık polarizasyon bir fonksiyonu olarak inceden inceye gözden geçirmek.</li>
</ol>

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Instrum. 87 (5), 053111 (2016).</li><li>Shimojima, T., Okazaki, K., Shin, S. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Low-temperature+and+high-energy-resolution+laser+photoemission+spectroscopy.">Low-temperature and high-energy-resolution laser photoemission spectroscopy.</a> J. Phys. Soc. Jpn. 84 (7), 072001 (2015).</li><li>Augustine, S., Mathai, E. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Growth,+morphology,+and+microindentation+analysis+of+Bi2Se3,+Bi1.8In0.2Se3,+and+Bi2Se2.8Te0.2+single+crystals.">Growth, morphology, and microindentation analysis of Bi2Se3, Bi1.8In0.2Se3, and Bi2Se2.8Te0.2 single crystals.</a> Mater. Res. Bull. 36 (13), 2251-2261 (2001).</li><li>Hasan, M. Z., Kane, C. 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Yazarlar onlar rakip hiçbir mali çıkarları var bildirin.

ARPES ve SARPES teknikleri elektronik grup yapıları grubu eşleme ve spin-algılama1,2ile çalışmak için yaygın olarak kullanılmaktadır. Yukarıda gösterilen bu genel avantajları yanı sıra lazer-SARPES optik dipol uyarma yörünge seçim kuralına göre wavefunction ve kuantum spin girişim spin-orbital kaplin yürürlükte görüntülenmesi için yeni bir teknik olarak istihdam edilebilir . Şekil 9 ve 10</stron...

Photoemission açı çözüldü spektroskopisi (ARPES) tekniği quasiparticle grup yapıları sağlam Birleşik1' deki araştırmak için en güçlü bir araç haline geldi. En iyi şekilde çekici özelliği ARPES, enerji ve momentum uzayda elektronik Birleşik karakterize etmek Grup eşleştirme için yeteneği var. Spin çözüldü ARPES (burada spin-dedektörleri, e.gile donatılmış SARPES). Mott dedektörü2,3, daha fazla spin karakter gözlenen grup yapıları4gidermek bize sağlar. Mott dedektörü spin iki eksen (x ve z, veya y ve z) ile ölçebilirsiniz beri iki Mott dedektörleri daha fazla kombinasyonu bir üç boyut4,5 spin yönde elde etmek izin verir . Birkaç on yıl için ancak, SARPES deneyler onların düşük verimlilik (genellikle 1/spin entegre ARPES ölçüm için kıyasla 10000) zarar3,4,5,6 ,7enerji ve açısal çözünürlük sınırlı oldu,. Son zamanlarda, SARPES enerji çözünürlüğe üzerinde exchange saçılma, sözde çok düşük enerjili elektron-kırınım (VLEED) dedektörü7,8,9 dayalı bir yüksek verimli spin dedektörü ile artış ,10. Bu dedektörü ile veri toplama süresi kısaltılmış ve veri kalitesi önemli ölçüde geliştirilmiştir. Son zamanlarda, SARPES büyük ölçüde elektronik Birleşik spin polarize ve özellikle spin-yörünge kaplin etkisi yüzey bantları7spin doku kaynaklanan adrese başarılı oldu.
Burada, biz SARPES istihdam ölçümleri bir kutuplaşma değişkenli vakum ultraviyole ile lazer ışığı (lazer-SARPES) ve bu kombine teknik büyük avantajları göstermektedir. Spin-yörünge birleştiğinde yüzey Birleşik BI2Se3soruşturma, biz iki lazer-SARPES yeteneklerini mevcut. İlk olarak, doğrusal polarize lazerler dipol geçiş rejimi, p- ve syörünge seçim kuralı nedeniyle-polarize ışık seçerek heyecanlandırmak eigen-wavefunctions farklı yörünge simetri ile bir parçası. Yörünge bir seçici uyarma SARPES, yani, orbital-seçici SARPES böylece kullanılabilir. İkinci olarak, üç boyutlu (3D) spin-algılama SARPES spin kuantum eksen yönünü gösterir ve doğrudan ışık-polarizasyon bağımlılığı tam bilgileri görüntüler. Bu iletişim kuralı kısaca güçlü spin-yörünge kaplin etkilerini incelemek için bu state-of--art lazer-SARPES teknik gerçekleştirmek için bir metodoloji açıklayın.
Lazer-SARPES sistemimiz Institute for Solid State fizik, Tokyo Üniversitesi11yer alır. Bizim lazer-SAPRES makine şematik çizim Şekil 1' de gösterilen. Polarizasyon değişkenli 7-eV lazer ışık12 örnek yüzeyi aydınlatan ve photoelectrons örnek yayılan. Lazer kutuplaşma otomatik olarak MgF2- tabanlı λ/2 - ve seçmeli olarak doğrusal ve dairesel kutuplaşmalar kullanmak için λ/4-waveplates tarafından kontrol edilir. Hemisferik elektron analyzer photoelectrons düzeltir ve onların kinetik enerji (Ekin) ve emisyon açı (çapx ve θy) analiz eder. Photoelectron yoğunluklarda Ekin- CCD kamera tarafından izlenençapx ekran üzerinde eşleştirilir. Bu görüntü doğrudan enerji grup yapısı karşılıklı uzayda dönüşüyor.
SARPES ölçüm, belirli emisyon açı ve kinetik enerji elektron Çözümleyicisi tarafından analiz ile photoelectrons iki VLEED tipi spin yangın dedektörleri ile 90 derece photoelectron saptırıcı için yönlendirilir ve photoelectron kirişler iki odaklanmıştır farklı hedefler filmlerin oksijen tarafından sona Fe(001) -p(1 × 1). Hedefler tarafından yansıyan photoelectrons her spin Dedektör yerleştirilen bir channeltron kullanarak tek kanal algılama ile tespit edilir. VLEED hedefleri saygı ile dik geometri ile düzenlenmiş olan Helmholtz tipi elektrikli bobinleri ile mıknatıslı olmalı. Mıknatıslama yönü iki kutuplu kondansatör banka tarafından denetlenir. Çift Kişilik VLEED spin Dedektör böylece bize photoelectron üç boyutlu spin-polarizasyon vektör analiz etmek etkinleştirin.

<table>
	<tbody>
		<tr>
			<td>DA30-L hemispherical analyzer</td>
			<td>ScientaOmicron</td>
			<td></td>
			<td>http://www.scientaomicron.com/en/products/353/1170</td>
		</tr>
		<tr>
			<td>Silver-based epoxy</td>
			<td>Epoxy Technology</td>
			<td>H20E</td>
			<td></td>
		</tr>
		<tr>
			<td>Sctoch tape</td>
			<td>3M</td>
			<td>801-1-18C</td>
			<td></td>
		</tr>
		<tr>
			<td>UHV valve</td>
			<td>VAT</td>
			<td>01034-KE01</td>
			<td></td>
		</tr>
		<tr>
			<td>linear/rotary feedthrough</td>
			<td>Ferrovac</td>
			<td>MD40</td>
			<td></td>
		</tr>
		<tr>
			<td>transfer rod</td>
			<td>UHV design</td>
			<td>PP series</td>
			<td></td>
		</tr>
		<tr>
			<td>wobble stick</td>
			<td>Ferrovac</td>
			<td>WM40</td>
			<td></td>
		</tr>
		<tr>
			<td>Paladin compact 355</td>
			<td>Coherent</td>
			<td></td>
			<td></td>
		</tr>
		<tr>
			<td>half waveplate</td>
			<td>Kogakugiken</td>
			<td></td>
			<td>order made</td>
		</tr>
		<tr>
			<td>Bipolar condenser bank</td>
			<td>Tsuji electronics</td>
			<td></td>
			<td></td>
		</tr>
	</tbody>
</table>

experimental methods for spin- and angle-resolved photoemission spectroscopy combined with polarization-variable laser

Bu protokolü nasıl spin ve açı çözüldü photoemission spektroskopisi polarizasyon değişkenli 7-eV lazer (lazer-SARPES) ile birlikte gerçekleştirmek için mevcut ve katı hal fiziği çalışmak için bu teknik bir güç göstermek için hedeftir. Lazer-SARPES iki büyük yetenekleri sağlar. İlk olarak, yörünge seçim kuralı doğrusal polarize lazerlerin inceleyerek, yörünge seçici uyarma SAPRES deneyde yürütülen olabilir. İkinci olarak, teknik bir varyasyon spin kuantum eksen ışık polarizasyon bir fonksiyonu olarak tam bilgi gösterir. Lazer-SARPES bu yetenekleri işbirliği gücünü göstermek için spin-yörünge birleştiğinde yüzey Birleşik BI2Se3araştırmalar için bu tekniği uygulamak. Bu teknik spin ve yörünge spin-yörünge birleştiğinde wavefunctions bileşenlerinden çürümeye affords. Ayrıca, doğrudan spin algılama kullanarak bir temsilci avantajı polarizasyon-değişken laser ile işbirliği gibi teknik belirsizliğe yer bırakmadan spin kuantum eksen üç-boyut ışık polarizasyon bağımlılığının görüntüler. Lazer-SARPES önemli ölçüde photoemission teknik kapasitesini artırır.

SARPES deneyler başlamadan önce k pozisyonlar yüksek hayatinizda spin entegre ARPES sonuçları yüksek enerji - ve açısal-çözünürlük ile (5.1-5,5 iletişim kuralı) kullanarak spektrum spin çözüldü almak için doğru bir şekilde belirlenecektir gerekir. Bu nerede bir bı2Se3 tek kristal ARPES sonuçları sunulmuştur Şekil 7 ' de gösterilmiştir. Bu malzeme bir spin polarize yüzey Birleşik14...

Watch this Scientific Journal Video about Experimental Methods for Spin- and Angle-Resolved Photoemission Spectroscopy Combined with Polarization-Variable Laser at JoVE.com

Experimental Methods for Spin- and Angle-Resolved Photoemission Spectroscopy Combined with Polarization-Variable Laser

Burada, polarizasyon değişkenli 7-eV lazer spin-orbital kaplin etkisi katı Birleşik Devletleri görselleştirmek için spin ve açı çözüldü photoemission tekniği ile birleştirir.

Spin ve açı çözüldü Photoemission spektroskopisi polarizasyon değişkenli lazer ile kombine için deneysel yöntemleri

The goal of this protocol is to present how to perform spin- and angle-resolved photoemission spectroscopy combined with polarization-variable 7-eV laser ...

experimental-methods-for-spin-angle-resolved-photoemission

Research

JoVE Journal

Engineering

9.8K Görüntüleme.  University of Tokyo. Burada, polarizasyon değişkenli 7-eV lazer spin-orbital kaplin etkisi katı Birleşik Devletleri görselleştirmek için spin ve açı çözüldü photoemission tekniği ile birleştirir.

Video: Experimental Methods for Spin- and Angle-Resolved Photoemission Spectroscopy Combined with Polarization-Variable Laser

Angle-resolved Photoemission Spectroscopy At Ultra-low Temperatures

The physical properties of a material are defined by its electronic structure. Electrons in solids are characterized by energy (&omega;) and momentum (k) and the probability to find them in a particular state with given &omega; and k is described by the spectral function A(k, &omega;). This function can be directly measured in an experiment based on the well-known photoelectric effect, for the explanation of which Albert Einstein received the Nobel Prize back in 1921. In the photoelectric effect the light shone on a surface ejects electrons from the material. According to Einstein, energy conservation allows one to determine the energy of an electron inside the sample, provided the energy of the light photon and kinetic energy of the outgoing photoelectron are known. Momentum conservation makes it also possible to estimate k relating it to the momentum of the photoelectron by measuring the angle at which the photoelectron left the surface. The modern version of this technique is called Angle-Resolved Photoemission Spectroscopy (ARPES) and exploits both conservation laws in order to determine the electronic structure, i.e. energy and momentum of electrons inside the solid. In order to resolve the details crucial for understanding the topical problems of condensed matter physics, three quantities need to be minimized: uncertainty* in photon energy, uncertainty in kinetic energy of photoelectrons and temperature of the sample.
In our approach we combine three recent achievements in the field of synchrotron radiation, surface science and cryogenics. We use synchrotron radiation with tunable photon energy contributing an uncertainty of the order of 1 meV, an electron energy analyzer which detects the kinetic energies with a precision of the order of 1 meV and a He3 cryostat which allows us to keep the temperature of the sample below 1 K. We discuss the exemplary results obtained on single crystals of Sr2RuO4 and some other materials. The electronic structure of this material can be determined with an unprecedented clarity.

The overall goal of this method is to determine the low-energy electronic structure of solids at ultra-low temperatures using Angle-Resolved Photoemission Spectroscopy with synchrotron radiation.

Ultra-düşük sıcaklıklarda Açı çözüldü Photoemission Spektroskopi

The physical properties of a material are defined by its  electronic structure. Electrons in solids are characterized by energy (&omega;)  and momentum ...

Mühendislik

Spatial Separation of Molecular Conformers and Clusters

Gas-phase molecular physics and physical chemistry experiments commonly use supersonic expansions through pulsed valves for the production of cold molecular beams. However, these beams often contain multiple conformers and clusters, even at low rotational temperatures. We present an experimental methodology that allows the spatial separation of these constituent parts of a molecular beam expansion. Using an electric deflector the beam is separated by its mass-to-dipole moment ratio, analogous to a bender or an electric sector mass spectrometer spatially dispersing charged molecules on the basis of their mass-to-charge ratio. This deflector exploits the Stark effect in an inhomogeneous electric field and allows the separation of individual species of polar neutral molecules and clusters. It furthermore allows the selection of the coldest part of a molecular beam, as low-energy rotational quantum states generally experience the largest deflection. Different structural isomers (conformers) of a species can be separated due to the different arrangement of functional groups, which leads to distinct dipole moments. These are exploited by the electrostatic deflector for the production of a conformationally pure sample from a molecular beam. Similarly, specific cluster stoichiometries can be selected, as the mass and dipole moment of a given cluster depends on the degree of solvation around the parent molecule. This allows experiments on specific cluster sizes and structures, enabling the systematic study of solvation of neutral molecules.

We present a technique that allows the spatial separation of different conformers or clusters present in a molecular beam. An electrostatic deflector is used to separate species by their mass-to-dipole moment ratio, leading to the production of gas-phase ensembles of a single conformer or cluster stoichiometry.

Moleküler Konformatörlerin ve Kümelerin Mekansal Ayrımı

Gas-phase molecular physics and physical chemistry experiments commonly use supersonic expansions through pulsed valves for the production of cold ...

Quantum State Engineering of Light with Continuous-wave Optical Parametric Oscillators

Engineering non-classical states of the electromagnetic field is a central quest for quantum optics1,2. Beyond their fundamental significance, such states are indeed the resources for implementing various protocols, ranging from enhanced metrology to quantum communication and computing. A variety of devices can be used to generate non-classical states, such as single emitters, light-matter interfaces or non-linear systems3. We focus here on the use of a continuous-wave optical parametric oscillator3,4. This system is based on a non-linear &#967;2 crystal inserted inside an optical cavity and it is now well-known as a very efficient source of non-classical light, such as single-mode or two-mode squeezed vacuum depending on the crystal phase matching. 
Squeezed vacuum is a Gaussian state as its quadrature distributions follow a Gaussian statistics. However, it has been shown that number of protocols require non-Gaussian states5. Generating directly such states is a difficult task and would require strong &#967;3 non-linearities. Another procedure, probabilistic but heralded, consists in using a measurement-induced non-linearity via a conditional preparation technique operated on Gaussian states. Here, we detail this generation protocol for two non-Gaussian states, the single-photon state and a superposition of coherent states, using two differently phase-matched parametric oscillators as primary resources. This technique enables achievement of a high fidelity with the targeted state and generation of the state in a well-controlled spatiotemporal mode.

We describe the reliable generation of non-Gaussian states of traveling optical fields, including single-photon states and coherent state superpositions, using a conditional preparation method operated on the non-classical light emitted by optical parametric oscillators. Type-I and type-II phase-matched oscillators are considered and common procedures, such as the required frequency filtering or the high-efficiency quantum state characterization by homodyning, are detailed.

Sürekli dalga Optik Parametrik Osilatörler ile Işığın kuantum Devlet Mühendislik

Engineering non-classical states of the electromagnetic field is a central quest for quantum optics1,2. Beyond their fundamental significance, such states ...

Laser-induced Breakdown Spectroscopy: A New Approach for Nanoparticle's Mapping and Quantification in Organ Tissue

Emission spectroscopy of laser-induced plasma was applied to elemental analysis of biological samples. Laser-induced breakdown spectroscopy (LIBS) performed on thin sections of rodent tissues: kidneys and tumor, allows the detection of inorganic elements such as (i) Na, Ca, Cu, Mg, P, and Fe, naturally present in the body and (ii) Si and Gd, detected after the injection of gadolinium-based nanoparticles. The animals were euthanized 1&#160;to 24 hr&#160;after intravenous injection of particles. A two-dimensional scan of the sample, performed using a motorized micrometric 3D-stage, allowed the infrared laser beam exploring the surface with a lateral resolution less than 100 &#956;m. Quantitative chemical images of Gd element inside the organ were obtained with sub-mM sensitivity. LIBS offers a simple and robust method to study the distribution of inorganic materials without any specific labeling. Moreover, the compatibility of the setup with standard optical microscopy emphasizes its potential to provide multiple images of the same biological tissue with different types of response:&#160;elemental, molecular, or cellular.

Laser-induced breakdown spectroscopy performed on thin organ and tumor tissue successfully detected natural elements and artificially injected gadolinium (Gd), issued from Gd-based nanoparticles. Images of chemical elements reached a resolution of 100 &#956;m and quantitative sub-mM sensitivity. The compatibility of the setup with standard optical microscopy emphasizes its potential to provide multiple images of a same biological tissue.

Lazer kaynaklı Arıza Spektroskopisi: Organ Doku Nanopartikülün en Mapping ve Nicelik için Yeni Bir Yaklaşım

Emission spectroscopy of laser-induced plasma was applied to elemental analysis of biological samples. Laser-induced breakdown spectroscopy (LIBS) ...

Proton Transfer and Protein Conformation Dynamics in Photosensitive Proteins by Time-resolved Step-scan Fourier-transform Infrared Spectroscopy

Monitoring the dynamics of protonation and protein backbone conformation changes during the function of a protein is an essential step towards understanding its mechanism. Protonation and conformational changes affect the vibration pattern of amino acid side chains and of the peptide bond, respectively, both of which can be probed by infrared (IR) difference spectroscopy. For proteins whose function can be repetitively and reproducibly triggered by light, it is possible to obtain infrared difference spectra with (sub)microsecond resolution over a broad spectral range using the step-scan Fourier transform infrared technique. With ~102-103 repetitions of the photoreaction, the minimum number to complete a scan at reasonable spectral resolution and bandwidth, the noise level in the absorption difference spectra can be as low as ~10-4, sufficient to follow the kinetics of protonation changes from a single amino acid. Lower noise levels can be accomplished by more data averaging and/or mathematical processing. The amount of protein required for optimal results is between 5-100 &#181;g, depending on the sampling technique used. Regarding additional requirements, the protein needs to be first concentrated in a low ionic strength buffer and then dried to form a film. The protein film is hydrated prior to the experiment, either with little droplets of water or under controlled atmospheric humidity. The attained hydration level (g of water / g of protein) is gauged from an IR absorption spectrum. To showcase the technique, we studied the photocycle of the light-driven proton-pump bacteriorhodopsin in its native purple membrane environment, and of the light-gated ion channel channelrhodopsin-2 solubilized in detergent.

Key steps of protein function, in particular backbone conformational changes and proton transfer reactions, often take place in the microsecond to millisecond time scale. These dynamical processes can be studied by time-resolved step-scan Fourier-transform infrared spectroscopy, in particular for proteins whose function is triggered by light.

Tarafından Işığa Proteinler Proton Transferi ve Protein Konformasyon Dynamics Zamanda çözülmüş kızılötesi spektroskopi Fourier-dönüşümü Step-tarama

Monitoring the dynamics of protonation and protein backbone conformation changes during the function of a protein is an essential step towards ...

Advanced Experimental Methods for Low-temperature Magnetotransport Measurement of Novel Materials

Novel electronic materials are often produced for the first time by synthesis processes that yield bulk crystals (in contrast to single crystal thin film synthesis) for the purpose of exploratory materials research. Certain materials pose a challenge wherein the traditional bulk Hall bar device fabrication method is insufficient to produce a measureable device for sample transport measurement, principally because the single crystal size is too small to attach wire leads to the sample in a Hall bar configuration. This can be, for example, because the first batch of a new material synthesized yields very small single crystals or because flakes of samples of one to very few monolayers are desired. In order to enable rapid characterization of materials that may be carried out in parallel with improvements to their growth methodology, a method of device fabrication for very small samples has been devised to permit the characterization of novel materials as soon as a preliminary batch has been produced. A slight variation of this methodology is applicable to producing devices using exfoliated samples of two-dimensional materials such as graphene, hexagonal boron nitride (hBN), and transition metal dichalcogenides (TMDs), as well as multilayer heterostructures of such materials. Here we present detailed protocols for the experimental device fabrication of fragments and flakes of novel materials with micron-sized dimensions onto substrate and subsequent measurement in a commercial superconducting magnet, dry helium close-cycle cryostat magnetotransport system at temperatures down to 0.300 K and magnetic fields up to 12 T.

We describe the methodology of mechanical exfoliation and deposition of flakes of novel materials with micron-sized dimensions onto substrate, fabrication of experimental device structures for transport experimentation, and the magnetotransport measurement in a dry helium close-cycle cryostat at temperatures down to 0.300 K and magnetic fields up to 12 T.

Yeni Malzemelerin Düşük sıcaklık Magnetotransport Ölçüm İleri Deneysel Yöntemler

Novel electronic materials are often produced for the first time by synthesis processes that yield bulk crystals (in contrast to single crystal thin film ...

SSVEP-based Experimental Procedure for Brain-Robot Interaction with Humanoid Robots

Brain-Robot Interaction (BRI), which provides an innovative communication pathway between human and a robotic device via brain signals, is prospective in helping the disabled in their daily lives. The overall goal of our method is to establish an SSVEP-based experimental procedure by integrating multiple software programs, such as OpenViBE, Choregraph, and Central software as well as user developed programs written in C++ and MATLAB, to enable the study of brain-robot interaction with humanoid robots.
This is achieved by first placing EEG electrodes on a human subject to measure the brain responses through an EEG data acquisition system. A user interface is used to elicit SSVEP responses and to display video feedback in the closed-loop control experiments. The second step is to record the EEG signals of first-time subjects, to analyze their SSVEP features offline, and to train the classifier for each subject. Next, the Online Signal Processor and the Robot Controller are configured for the online control of a humanoid robot. As the final step, the subject completes three specific closed-loop control experiments within different environments to evaluate the brain-robot interaction performance.
The advantage of this approach is its reliability and flexibility because it is developed by integrating multiple software programs. The results show that using this approach, the subject is capable of interacting with the humanoid robot via brain signals. This allows the mind-controlled humanoid robot to perform typical tasks that are popular in robotic research and are helpful in assisting the disabled.

The overall goal of this method is to establish an SSVEP-based experimental procedure by integrating multiple software programs to enable the study of brain-robot interaction with humanoid robots, which is prospective in assisting the sick and elderly as well as performing unsanitary or dangerous jobs.

İnsansı Robotlar ile Beyin Robot Etkileşimi Deneysel Prosedür SSVEP tabanlı

Brain-Robot Interaction (BRI), which provides an innovative communication pathway between human and a robotic device via brain signals, is prospective in ...

Experimental Methods for Investigation of Shape Memory Based Elastocaloric Cooling Processes and Model Validation

Shape Memory Alloys (SMA) using elastocaloric cooling processes have the potential to be an environmentally friendly alternative to the conventional vapor compression based cooling process. Nickel-Titanium (Ni-Ti) based alloy systems, especially, show large elastocaloric effects. Furthermore, exhibit large latent heats which is a necessary material property for the development of an efficient solid-state based cooling process. A scientific test rig has been designed to investigate these processes and the elastocaloric effects in SMAs. The realized test rig enables independent control of an SMA&#39;s mechanical loading and unloading cycles, as well as conductive heat transfer between SMA cooling elements and a heat source/sink. The test rig is equipped with a comprehensive monitoring system capable of synchronized measurements of mechanical and thermal parameters. In addition to determining the process-dependent mechanical work, the system also enables measurement of thermal caloric aspects of the elastocaloric cooling effect through use of a high-performance infrared camera. This combination is of particular interest, because it allows illustrations of localization and rate effects &#8212; both important for efficient heat transfer from the medium to be cooled.
The work presented describes an experimental method to identify elastocaloric material properties in different materials and sample geometries. Furthermore, the test rig is used to investigate different cooling process variations. The introduced analysis methods enable a differentiated consideration of material, process and related boundary condition influences on the process efficiency. The comparison of the experimental data with the simulation results (of a thermomechanically coupled finite element model) allows for better understanding of the underlying physics of the elastocaloric effect. In addition, the experimental results, as well as the findings based on the simulation results, are used to improve the material properties.

Experimental methods for investigation of solid state cooling processes and characterization of elastocaloric material properties of Shape Memory Alloys (SMA) are presented. A custom-built test rig has been designed for controlling and comprehensive monitoring of elastocaloric cooling processes. Furthermore, it provides a validation platform for thermomechanically coupled modeling approaches.

Şekil Bellek İncelenmesi Tabanlı Elastocaloric Soğutma Süreçler ve Model Doğrulama için Deneysel Yöntemler

Shape Memory Alloys (SMA) using elastocaloric cooling processes have the potential to be an environmentally friendly alternative to the conventional vapor ...

Compact Lens-less Digital Holographic Microscope for MEMS Inspection and Characterization

A micro-electro-mechanical-system (MEMS) is a widely used component in many industries, including energy, biotechnology, medical, communications, and automotive. However, effective inspection and characterization metrology systems are needed to ensure the functional reliability of MEMS. This study presents a system based on digital holography as a tool for MEMS metrology. Digital holography has gained increasing attention in the past 20 years. With the fast development and decreasing cost of sensor arrays, resolution of such systems has increased broadening potential applications. Thus, it has attracted attention from both research and industry sides as a potential reliable tool for industrial metrology. Indeed, by recording the interference pattern between an object beam (which contains sample height information) and a reference beam on a CCD camera, one can retrieve the quantitative phase information of an object. However, most of digital holographic systems are bulky and thus not easy to implement on industry production lines. The novelty of the system presented is that it is lens-less and thus very compact. In this study, it is shown that the Compact Digital Holographic Microscope (CDHM) can be used to evaluate several characteristics typically consider as criteria in MEMS inspections. The surface profiles of MEMS in both static and dynamic conditions are presented. Comparison with AFM is investigated to validate the accuracy of the CDHM.

We present a compact reflection digital holographic system (CDHM) for inspection and characterization of MEMS devices. A lens-less design using a diverging input wave providing natural geometrical magnification is demonstrated. Both static and dynamic studies are presented.

MEMS Muayene ve Karakterizasyonu için kompakt Lens az Dijital Holografik Mikroskop

A micro-electro-mechanical-system (MEMS) is a widely used component in many industries, including energy, biotechnology, medical, communications, and ...

Free-form Light Actuators &#8212; Fabrication and Control of Actuation in Microscopic Scale

Liquid crystalline elastomers (LCEs) are smart materials capable of reversible shape-change in response to external stimuli, and have attracted researchers&#39; attention in many fields. Most of the studies focused on macroscopic LCE structures (films, fibers) and their miniaturization is still in its infancy. Recently developed lithography techniques, e.g., mask exposure and replica molding, only allow for creating 2D structures on LCE thin films. Direct laser writing (DLW) opens access to truly 3D fabrication in the microscopic scale. However, controlling the actuation topology and dynamics at the same length scale remains a challenge.
In this paper we report on a method to control the liquid crystal (LC) molecular alignment in the LCE microstructures of arbitrary three-dimensional shape. This was made possible by a combination of direct laser writing for both the LCE structures as well as for micrograting patterns inducing local LC alignment. Several types of grating patterns were used to introduce different LC alignments, which can be subsequently patterned into the LCE structures. This protocol allows one to obtain LCE microstructures with engineered alignments able to perform multiple opto-mechanical actuation, thus being capable of multiple functionalities. Applications can be foreseen in the fields of tunable photonics, micro-robotics, lab-on-chip technology and others.

Here, we fabricate 3D polymeric micro/nano structures in which both the shape and the molecular alignment can be engineered with nanometer scale accuracy by the use of direct laser writing. Light induced deformation of several types of liquid crystalline elastomer microstructures can be controlled in the microscopic scale.