The Mit Specular and Diffuse Neutron Reflectometer for the Investigation of Surfaces & Interfaces

1994 ◽  
Vol 376 ◽  
Author(s):  
Chwen-Yuan Ku ◽  
Xiao-Lin Zhou
Keyword(s):  
Nuclear Reactor ◽  
Dynamic Range ◽  
Sample Surface ◽  
Massachusetts Institute Of Technology ◽  
Neutron Reflectometer ◽  
Wide Range ◽  
Diffuse Reflectivity ◽  
Institute Of Technology ◽  
Beam Motion ◽  
Diffuse Neutron

ABSTRACTA specular and diffuse neutron reflectometer was designed at the Massachusetts Institute of Technology nuclear reactor, MITR-II, and the description of the facility is presented in this paper. This reflectometer uses a horizontal sample geometry so that both solid and liquid samples can be measured. To minimize sample or beam motion and reduce measurement time, two neutron beams are extracted from the same beam port and are incident simultaneously on the same sample surface at grazing incident angles of 0.2 and 1.5 degrees, respectively. The reflected neutrons are detected by a linear position sensitive detector and energy-analyzed by the time-of-flight method. The reflection flight path is enclosed in an evacuated chamber to reduce background counts. The reflectometer performance is estimated as 0.004-0.33 Å-1 dynamic range, 5% Q resolution, 1-10-7 measurable specular reflectivity range, and a 4 orders of magnitude range in diffuse reflectivity counts. Diffuse reflectivity can be measured as a two-dimensional function of both the wavelength and the in-plane diffuse reflection angle. The instrument can be used to investigate a wide range of surface systems of condensed and soft-condensed matters.

Ferroelectricity: The Foundation of a Field from Form to Function

MRS Bulletin ◽  
2005 ◽  
Vol 30 (11) ◽  
pp. 845-848 ◽  
Author(s):  
R.E. Newnham ◽  
L. Eric Cross
Keyword(s):  
Perovskite Structure ◽  
Mixed Oxides ◽  
The United States ◽  
Molecular Engineering ◽  
Temperature Phase ◽  
Massachusetts Institute Of Technology ◽  
Domain Structures ◽  
Wide Range ◽  
Sonar Systems ◽  
Institute Of Technology

AbstractThis article highlights the major role Arthur von Hippel and the Laboratory for Insulation Research at the Massachusetts Institute of Technology played in the early development of the field of ferroelectricity in mixed oxides with the perovskite structure and, in particular, in the identification of ferroelectricity in barium titanate following its discovery in industrial laboratories in the United States during World War II.Very early optical and x-ray studies highlighted the characteristics of the ferroelectric domain structures in both ceramic and single-crystal BaTiO3, the elimination of domains at the Curie temperature TC, and the salient characteristics of the two low-temperature phase transitions. Perhaps the culmination of this work was the detailed studies of lamella 90° domains by Peter Forsbergh and the gorgeous patterns these could generate. This article also traces the manner in which the early studies contributed to whole industries based on perovskite ferroelectrics. The ceramic capacitor industry is now fabricating sophisticated, cofired multilayer capacitors (MLCs) with up to a thousand 1-µm-thick dielectric layers interleaved with base metal electrodes, addressing a market for some 1013 capacitors per year.Manufacturers of large piezoelectric transducers depend almost exclusively on perovskite-structure oxide ceramics. Navy sonar systems are major customers, but spinoff has occurred into a wide range of commercial and medical ultrasound systems. The capability of current materials has improved more than tenfold over the original BaTiO3 ceramics as a result of the effective application of molecular engineering, a strong testament to the insight of the founder of this area of study.

16 Noninvasive deep brain stimulation via delivery of temporally interfering electric fields

2020 ◽  
Vol 91 (8) ◽  
pp. e6.3-e7
Author(s):  
Nir Grossman
Keyword(s):  
Electric Field ◽  
Electric Fields ◽  
Brain Stimulation ◽  
Dynamic Range ◽  
Imperial College ◽  
Network Activity ◽  
Massachusetts Institute Of Technology ◽  
Neural Firing ◽  
Institute Of Technology ◽  
The Brain

Nir is a Lecturer (Assistant Professor) at Imperial College London and a founding fellow of the UK Dementia Research Institute (UK-DRI). The long-term goal of his research is to develop neuromodulatory interventions for neurodegenerative diseases by direct modulation of the underlying aberrant network activity. Nir received a BSc in Physics from the Israeli Institute of Technology (Technion), an MSc in Electromagnetic Engineering from the Technical University of Hamburg-Harburg, and a PhD in Neuroscience from Imperial College London. He then completed a postdoc training, as a Wellcome Trust Fellow, at the Massachusetts Institute of Technology (MIT) and Harvard University. Nir was recently awarded the prestige prize for Neuromodulation from the Science magazine for describing how temporal interfering of kHz electric fields can non-invasively stimulate focal neural structures deep in the brain.Electrical brain stimulation is a key technique in research and clinical neuroscience studies, and also is in increasingly widespread use from a therapeutic standpoint. However, to date all methods of electrical stimulation of the brain either require surgery to implant an electrode at a defined site, or involve the application of non-focal electric fields to large fractions of the brain. We report a noninvasive strategy for electrically stimulating neurons at depth. By delivering to the brain multiple electric fields at frequencies too high to recruit neural firing, but which differ by a frequency within the dynamic range of neural firing, we can electrically stimulate neurons throughout a region where interference between the multiple fields results in a prominent electric field envelope modulated at the difference frequency. We validated this temporal interference (TI) concept via modeling and physics experiments, and verified that neurons in the living mouse brain could follow the electric field envelope. We demonstrate the utility of TI stimulation by stimulating neurons in the hippocampus of living mice without recruiting neurons of the overlying cortex. Finally, we show that by altering the currents delivered to a set of immobile electrodes, we can steerably evoke different motor patterns in living mice.

scholarly journals Integrated water vapour from GPS

MAUSAM ◽  
2021 ◽  
Vol 58 (1) ◽  
pp. 101-106
Author(s):  
R. K. GIRI ◽  
L. R. MEENA ◽  
S. S. BHANDARI ◽  
R. C. BHATIA
Keyword(s):  
Water Vapour ◽  
Global Climate ◽  
Spatial Scales ◽  
Limited Area ◽  
Gps Data ◽  
Massachusetts Institute Of Technology ◽  
Stochastic Filtering ◽  
Wide Range ◽  
Integrated Water Vapour ◽  
Institute Of Technology

Water vapour is highly variable in space and time, and plays a large role in atmospheric processes that act over a wide range of temporal and spatial scales on global climate to micrometeorology. This paper deals with a new approach to remotely sense the water vapour based on the Global Position System (GPS). The signal propagating from GPS satellites to ground based receivers is delayed by atmospheric water vapour. The delay is parameterized in terms of time varying Zenith-Wet Delay (ZWD), which is retrieved by stochastic filtering of GPS data. With the help of surface pressure and temperature readings at the GPS receiver, the retrieved ZWD can be transformed into Integrated Water Vapour (IWV) overlying at the receiver with little additional uncertainties. In this study the Zenith Total time Delay (ZTD) data without met package is retrieved using the GAMIT (King and Bock, 1997) GPS data processing software developed by Massachusetts Institute of Technology (MIT) for the period of January 2003 to February 2003 for two stations New Delhi and Bangalore .The IWV retrieved from GPS and its comparison with Limited Area Model (LAM) retrieved IWV shows fairly good agreement.

Preface

2009 ◽  
Vol 81 (12) ◽  
pp. iv
Author(s):  
Bryan R. Henry
Keyword(s):  
Molecular Electronics ◽  
Gas Adsorption ◽  
Dna Nanotechnology ◽  
Porous Metal ◽  
Massachusetts Institute Of Technology ◽  
Max Planck ◽  
Past President ◽  
Selection Committee ◽  
Wide Range ◽  
Institute Of Technology

IUPAC is a global, scientific organization that contributes to the worldwide understanding of chemistry and the chemical sciences. It is certainly true that young chemists are shaping our science, and it is important for IUPAC to provide encouragement to our young colleagues. IUPAC accomplishes this goal through the IUPAC Prize for Young Chemists. This prestigious annual prize honors four to five chemists for important and outstanding research carried out during recent Ph.D. studies. The work is mainly judged on the basis of a 1000-word essay which is supported by recommendations from the senior scientist(s) with whom the candidate collaborated.As immediate Past President of IUPAC, I have had the pleasure of chairing an international prize selection committee of eminent chemists with a wide range of expertise in chemistry that adjudicated essays from 36 applicants from 19 countries. Reading these outstanding essays provided a wonderful overview of new trends in chemistry. Due to the large number of excellent candidates, it was not an easy task to pick the winners, but in the end the committee arrived at a unanimous decision and awarded the 2009 IUPAC Prize for Young Chemists to the following five chemists:- Faisal A. Aldaye, McGill University, Montréal, Canada; "Supramolecular DNA nanotechnology: Discrete nanoparticle organization, three dimensional DNA construction, and molecule-mediated DNA self-assembly"- Christopher Bettinger, Massachusetts Institute of Technology, Cambridge, MA, USA; "Synthesis and microfabrication of elastomeric biomaterials for advanced tissue engineering scaffolds"- Xinliang Feng, Max Planck Institute for Polymer Research, Mainz, Germany: "C3-symmetric discotic liquid-crystalline materials for molecular electronics: Versatile synthesis and self-organization"- Xing Yi Ling, University of Twente, Enschede, The Netherlands: "From supramolecular chemistry to nanotechnology: Assembly of 3D nanostructures"- Shengqian Ma, Miami University, Oxford, OH, USA; "Gas adsorption applications of porous metal–organic frameworks"Each winner received a cash prize of USD 1000 and a trip to the 42nd IUPAC World Chemistry Congress, which took place in Glascow, Scotland, 2-7 August, 2009. Here the winners had the opportunity to present their work, which is an important stage of any research project. The prize winners also were invited to submit manuscripts on aspects of their research for publication in Pure and Applied Chemistry (PAC). It is a pleasure to see that all five prize winners have taken advantage of this offer. The result is five refereed papers which contain critical reviews of high quality and appear in PAC.Finally, it is an honor and a pleasure to congratulate each of the winners (and their supervisors) for winning the 2009 IUPAC Prize. It is IUPAC's hope that each of them has been encouraged to continue to do exciting research that will contribute to a bright future for the molecular-based sciences, which are so important for our common future.Bryan R. HenryIUPAC Immediate Past President and Chair of the IUPAC Prize Selection Committee

Scanning tunneling microscopy of polymers: A status report

1989 ◽  
Vol 47 ◽  
pp. 330-331
Author(s):  
P.E. Russell ◽  
I.H. Musselman
Keyword(s):  
High Resolution ◽  
Scanning Tunneling Microscopy ◽  
Sample Surface ◽  
Atomic Scale ◽  
Constant Current ◽  
Scanning Tunneling ◽  
Status Report ◽  
Tunneling Microscopy ◽  
Research Issues ◽  
Wide Range

Scanning tunneling microscopy (STM) has evolved rapidly in the past few years. Major developments have occurred in instrumentation, theory, and in a wide range of applications. In this paper, an overview of the application of STM and related techniques to polymers will be given, followed by a discussion of current research issues and prospects for future developments. The application of STM to polymers can be conveniently divided into the following subject areas: atomic scale imaging of uncoated polymer structures; topographic imaging and metrology of man-made polymer structures; and modification of polymer structures. Since many polymers are poor electrical conductors and hence unsuitable for use as a tunneling electrode, the related atomic force microscopy (AFM) technique which is capable of imaging both conductors and insulators has also been applied to polymers.The STM is well known for its high resolution capabilities in the x, y and z axes (Å in x andy and sub-Å in z). In addition to high resolution capabilities, the STM technique provides true three dimensional information in the constant current mode. In this mode, the STM tip is held at a fixed tunneling current (and a fixed bias voltage) and hence a fixed height above the sample surface while scanning across the sample surface.

Applying the Anderson-Darling Test to Suicide Clusters

Crisis ◽  
2013 ◽  
Vol 34 (6) ◽  
pp. 434-437 ◽  
Author(s):  
Donald W. MacKenzie
Keyword(s):  
Poisson Process ◽  
Goodness Of Fit ◽  
Small Samples ◽  
Massachusetts Institute Of Technology ◽  
Homogeneous Poisson Process ◽  
Cornell University ◽  
The Difference ◽  
Suicide Clusters ◽  
Institute Of Technology ◽  
Anderson Darling

Background: Suicide clusters at Cornell University and the Massachusetts Institute of Technology (MIT) prompted popular and expert speculation of suicide contagion. However, some clustering is to be expected in any random process. Aim: This work tested whether suicide clusters at these two universities differed significantly from those expected under a homogeneous Poisson process, in which suicides occur randomly and independently of one another. Method: Suicide dates were collected for MIT and Cornell for 1990–2012. The Anderson-Darling statistic was used to test the goodness-of-fit of the intervals between suicides to distribution expected under the Poisson process. Results: Suicides at MIT were consistent with the homogeneous Poisson process, while those at Cornell showed clustering inconsistent with such a process (p = .05). Conclusions: The Anderson-Darling test provides a statistically powerful means to identify suicide clustering in small samples. Practitioners can use this method to test for clustering in relevant communities. The difference in clustering behavior between the two institutions suggests that more institutions should be studied to determine the prevalence of suicide clustering in universities and its causes.

Editorial: Advancing the Debate on Architecture, Planning, and Built Environment Research

2015 ◽  
Vol 9 (2) ◽  
Author(s):  
Ashraf M. Salama
Keyword(s):  
Learning Styles ◽  
Cultural Values ◽  
Urban Studies ◽  
Wide Spectrum ◽  
Journal Ranking ◽  
Massachusetts Institute Of Technology ◽  
Open Access Journals ◽  
Practice Based Research ◽  
Institute Of Technology ◽  
Number Of Citations

With an acceptance rate that does not exceed 25% of the total papers and articles submitted to the journal, IJAR – International Journal of Architectural Research is moving forward to position itself among the leading journals in architecture and urban studies worldwide. As this is the case since the beginning of volume 5, issue 1, March 2011, one must note that the journal has been covered by several data and index bases since its inception including Avery Index to Architectural Periodicals, EBSCO-Current Abstracts-Art and Architecture, INTUTE, Directory of Open Access Journals, Pro-Quest, Scopus-Elsevier and many university library databases across the globe. This is coupled with IJAR being an integral part of the archives and a featured collection of ArchNet and the Aga Khan Documentation Centre at MIT: Massachusetts Institute of Technology, Cambridge, MA.In 2014, IJAR was included in Quartile 2 / Q2 list of Journals both in ‘Architecture’ and ‘Urban Studies.’ As of May 2015, IJAR is ranked 23 out of 83 journals in ‘Architecture’ and 59 out of 119 in ‘Urban Studies.’ Rankings are based on the SJR (SCImago Journal Ranking); an Elsevier- SCOPUS indicator that measures the scientific influence of the average article in a journal. SJR is a measure of scientific influence of scholarly journals that accounts for both the number of citations received by a journal and the importance or prestige of the journals where such citations come from. See here for more information (http://www.scimagojr.com/index.php) and (http://www.journalmetrics.com/sjr.php). While the journal is now on top of many of the distinguished journals in Elsevier- SCOPUS database, we will keep aspiring to sustain our position and move forward to Q1 group list and eventually in the top 10 journal list in the field. However, this requires sustained efforts and conscious endeavours that give attention to quality submissions through a rigorous review process. This edition of IJAR: volume 9, issue 2, July 2015 includes debates on a wide spectrum of issues, explorations and investigations in various settings. The issue encompasses sixteen papers addressing cities, settlements, and projects in Europe, South East Asia, and the Middle East. Papers involve international collaborations evidenced by joint contributions and come from scholars in universities, academic institutions, and practices in Belgium; Egypt; Greece; Italy; Jordan; Malaysia; Palestine; Qatar; Saudi Arabia; Serbia; Spain; Turkey; and the United Kingdom. In this editorial I briefly outline the key issues presented in these papers, which include topics relevant to social housing, multigenerational dwelling, practice-based research, sustainable design and biomimetic models, learning environments and learning styles, realism and the post modern condition, development and planning, urban identity, contemporary landscapes, and cultural values and traditions.

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