scholarly journals The synthetic versatility of the Tiffeneau–Demjanov chemistry in homologation tactics

2019 ◽  
Vol 150 (12) ◽  
pp. 2011-2019 ◽  
Author(s):  
Stefan M. Kohlbacher ◽  
Vivien-Sandra Ionasz ◽  
Laura Ielo ◽  
Vittorio Pace
Keyword(s):  
Diazo Compounds ◽  
Ring Extension ◽  
Ring Contraction ◽  
Simple Rules ◽  
Steric Factors ◽  
Rearrangement Process ◽  
High Level ◽  
Interesting Alternative

Abstract The Tiffeneau–Demjanov rearrangement can be regarded as an interesting alternative to the more common semi-pinacol transposition. It is usually employed for ring extension but, under specific conditions, it can also be used for ring contraction. Compared to other techniques, such as the Demjanov rearrangement or homologations with diazo compounds, the Tiffeneau–Demjanov pathway presents attractive features including high yielding and selective processes. Ring enlargements follow very strict and simple rules, such as the movement of the less substituted carbon and retention of the configuration. The rearrangement process is mainly affected by steric factors, due to presence of neighbouring groups, rather than electronic ones. The ring contraction may be achieved positioning the amine within the ring, thus achieving a high level of control. Unfortunately, applications of the reaction in modern homologation chemistry are rare; therefore, the aim of the review is re-proposing to the synthetic community the versatility of this venerable reaction and thus, spurring its employment for tackling challenging homologations processes. Graphic abstract

Information technology outsourcing and architecture dynamic capabilities as enablers of organizational agility

2019 ◽  
Vol 34 (2) ◽  
pp. 129-159 ◽  
Author(s):  
Forough Karimi-Alaghehband ◽  
Suzanne Rivard
Keyword(s):  
Information Technology ◽  
Dynamic Capabilities ◽  
It Services ◽  
Organizational Agility ◽  
It Architecture ◽  
Simple Rules ◽  
It Department ◽  
Information Technology Outsourcing ◽  
High Level ◽  
Case Data

Grounded in the dynamic capabilities perspective, our study addresses the question of how information technology outsourcing capabilities can interact with other IT strategic capabilities to enable organizational agility through the ongoing reconfiguration of IT solutions. To answer our question, we built on the notion of microfoundations that undergird the high-level dynamic capabilities of sensing, seizing, and reconfiguring. Adopting a theory elaboration approach, we studied the case of a firm evolving in a turbulent environment, which had outsourced the quasi-totality of its IT services and had a mature IT architecture. From the case data, we specify two types of microfoundations: repeatability-related microfoundations (i.e. processes) and ability-related microfoundations (i.e. IT department structure, skills, simple rules, and communications) that undergird either information technology outsourcing dynamic capabilities or IT architecture dynamic capabilities. We propose a model that outlines how the interaction between repeatability-related microfoundations, supported by ability-related microfoundations, enables the reconfiguration of IT solutions. Our study also elucidates how a firm can follow a logic of opportunity enabled by their IT outsourcing and IT architecture dynamic capabilities.

Thermolyse und Photolyse von cyclischen Diazoverbindungen [1] / Thermolysis and Photolysis of Cyclic Diazo Compounds [1]

1996 ◽  
Vol 51 (9) ◽  
pp. 1325-1333 ◽  
Author(s):  
Hans-Dietrich Stachel ◽  
Hermann Poschenrieder ◽  
Jutta Redlin
Keyword(s):  
Butyl Alcohol ◽  
Diazo Compounds ◽  
Wolff Rearrangement ◽  
Ring Contraction ◽  
Tert Butyl ◽  
Tert Butyl Alcohol

The rhodium-catalyzed decomposition of the diazoketones 4 in tert-butyl alcohol at 130 °C furnishes the m onoenolethers 5 and, after deprotection, the aci-reductones 6. In absence of intercepting agents the intermediate carbenes preferentially undergo Wolff rearrangement with ring contraction. In this case the β-thiolactone 10b or the β-lactone 13 or the β-lactam 14 are thermolysis products of the corresponding diazoketones. During photolysis of the diazoketones 4d/4g in presence of alcohols the 2-azetidinones 10c/d are formed.

scholarly journals Defining the Structural Stability Field of Disordered Fluorite Oxides

2021 ◽  
Vol 9 ◽  
Author(s):  
Eric C. O’Quinn ◽  
Devon L. Drey ◽  
Maik K. Lang
Keyword(s):  
Ionic Crystal ◽  
Fluorite Structure ◽  
Stability Field ◽  
Chemical Compositions ◽  
Radiation Fields ◽  
Energy Technologies ◽  
Ionic Substitution ◽  
Simple Rules ◽  
High Level ◽  
Intense Radiation

Fluorite-structured oxides constitute an important class of materials for energy technologies. Despite their high level of structural symmetry and simplicity, these materials can accommodate atomic disorder without losing crystallinity, making them indispensable for uses in environments with high temperature, changing chemical compositions, or intense radiation fields. In this contribution, we present a set of simple rules that predict whether a compound may adopt a disordered fluorite structure. This approach is closely aligned with Pauling’s rules for ionic crystal structures and Goldschmidt’s rules for ionic substitution.

scholarly journals Airborne, Autonomous & Collaborative

2011 ◽  
Vol 133 (04) ◽  
pp. 26-31 ◽  
Author(s):  
Brandon Basso ◽  
Joshua Love ◽  
J. Karl Hedrick
Keyword(s):  
Unmanned Aerial Vehicles ◽  
Moving Objects ◽  
Nearest Neighbor ◽  
Heuristic Algorithms ◽  
Leading Edge ◽  
Common Goal ◽  
Multiple Sensors ◽  
Simple Rules ◽  
High Level ◽  
Flying Robots

This article describes how collaboration of unmanned aerial vehicles (UAVs) can be done to achieve a common goal. With UAVs becoming both cheap and easy to build, the field's leading edge is now collaborating squadrons of two or five or ten aircrafts, to achieve a common goal. The ambition is to use teams of flying robots to develop vision-based maps of large areas, track moving objects, fuse information from multiple aircraft and multiple sensors, and perform high-level task planning. One form of collaboration consists of enabling teams of UAVs to work together on a task that would be impossible with only one UAV. The next extension of UAV collaboration is to enable the vehicles to work together on several tasks at the same time. It is possible to have a human user manually assign individual UAVs to specific tasks. Automated allocation can also be done through heuristic algorithms, such as the nearest-neighbor approach, which assigns the UAV closest to the task. The heuristics produce simple rules that behave predictably, but not necessarily optimally.

Effect of strain on ADF-STEM high-resolution images

1991 ◽  
Vol 49 ◽  
pp. 666-667
Author(s):  
M. Kelly ◽  
D.M. Bird
Keyword(s):  
High Resolution ◽  
Strong Influence ◽  
Intensity Variation ◽  
Dark Field ◽  
Atomic Resolution ◽  
Strain Fields ◽  
High Resolution Image ◽  
Annular Dark Field ◽  
High Resolution Images ◽  
Interesting Alternative

It is well known that strain fields can have a strong influence on the details of HREM images. This, for example, can cause problems in the analysis of edge-on interfaces between lattice mismatched materials. An interesting alternative to conventional HREM imaging has recently been advanced by Pennycook and co-workers where the intensity variation in the annular dark field (ADF) detector is monitored as a STEM probe is scanned across the specimen. It is believed that the observed atomic-resolution contrast is correlated with the intensity of the STEM probe at the atomic sites and the way in which this varies as the probe moves from cell to cell. As well as providing a directly interpretable high-resolution image, there are reasons for believing that ADF-STEM images may be less suseptible to strain than conventional HREM. This is because HREM images arise from the interference of several diffracted beams, each of which is governed by all the excited Bloch waves in the crystal.

Transcription factor/DNA interactions visualized by electron spectroscopic imaging

1992 ◽  
Vol 50 (1) ◽  
pp. 450-451
Author(s):  
David P. Bazett-Jones ◽  
Mark L. Brown
Keyword(s):  
Transcription Factor ◽  
Dna Sequences ◽  
Transcription Initiation ◽  
Molecular Mechanisms ◽  
Phosphorus Content ◽  
Spectroscopic Imaging ◽  
Electron Spectroscopic Imaging ◽  
Dna Backbone ◽  
Two Parameters ◽  
High Level

A multisubunit RNA polymerase enzyme is ultimately responsible for transcription initiation and elongation of RNA, but recognition of the proper start site by the enzyme is regulated by general, temporal and gene-specific trans-factors interacting at promoter and enhancer DNA sequences. To understand the molecular mechanisms which precisely regulate the transcription initiation event, it is crucial to elucidate the structure of the transcription factor/DNA complexes involved. Electron spectroscopic imaging (ESI) provides the opportunity to visualize individual DNA molecules. Enhancement of DNA contrast with ESI is accomplished by imaging with electrons that have interacted with inner shell electrons of phosphorus in the DNA backbone. Phosphorus detection at this intermediately high level of resolution (≈lnm) permits selective imaging of the DNA, to determine whether the protein factors compact, bend or wrap the DNA. Simultaneously, mass analysis and phosphorus content can be measured quantitatively, using adjacent DNA or tobacco mosaic virus (TMV) as mass and phosphorus standards. These two parameters provide stoichiometric information relating the ratios of protein:DNA content.

Advances in Stem Instrumentation for Biology

1990 ◽  
Vol 48 (1) ◽  
pp. 362-363
Author(s):  
J. S. Wall
Keyword(s):  
Scanning Transmission Electron Microscope ◽  
Carbon Films ◽  
Specimen Preparation ◽  
Material Deposition ◽  
Active User ◽  
Percent Improvement ◽  
Scanning Transmission ◽  
The Moment ◽  
Film Substrate ◽  
High Level

The forte of the Scanning transmission Electron Microscope (STEM) is high resolution imaging with high contrast on thin specimens, as demonstrated by visualization of single heavy atoms. of equal importance for biology is the efficient utilization of all available signals, permitting low dose imaging of unstained single molecules such as DNA.Our work at Brookhaven has concentrated on: 1) design and construction of instruments optimized for a narrow range of biological applications and 2) use of such instruments in a very active user/collaborator program. Therefore our program is highly interactive with a strong emphasis on producing results which are interpretable with a high level of confidence.The major challenge we face at the moment is specimen preparation. The resolution of the STEM is better than 2.5 A, but measurements of resolution vs. dose level off at a resolution of 20 A at a dose of 10 el/A2 on a well-behaved biological specimen such as TMV (tobacco mosaic virus). To track down this problem we are examining all aspects of specimen preparation: purification of biological material, deposition on the thin film substrate, washing, fast freezing and freeze drying. As we attempt to improve our equipment/technique, we use image analysis of TMV internal controls included in all STEM samples as a monitor sensitive enough to detect even a few percent improvement. For delicate specimens, carbon films can be very harsh-leading to disruption of the sample. Therefore we are developing conducting polymer films as alternative substrates, as described elsewhere in these Proceedings. For specimen preparation studies, we have identified (from our user/collaborator program ) a variety of “canary” specimens, each uniquely sensitive to one particular aspect of sample preparation, so we can attempt to separate the variables involved.

A Questionnaire Survey of Current Rehabilitation Practices for Adults With Normal Hearing Sensitivity Who Experience Auditory Difficulties

2020 ◽  
Vol 29 (4) ◽  
pp. 738-761
Author(s):  
Tess K. Koerner ◽  
Melissa A. Papesh ◽  
Frederick J. Gallun
Keyword(s):  
Hearing Aids ◽  
Questionnaire Survey ◽  
Patient Population ◽  
Clinical Care ◽  
Normal Hearing ◽  
Auditory Training ◽  
Training Methods ◽  
Hearing Sensitivity ◽  
Considerable Benefit ◽  
High Level

Purpose A questionnaire survey was conducted to collect information from clinical audiologists about rehabilitation options for adult patients who report significant auditory difficulties despite having normal or near-normal hearing sensitivity. This work aimed to provide more information about what audiologists are currently doing in the clinic to manage auditory difficulties in this patient population and their views on the efficacy of recommended rehabilitation methods. Method A questionnaire survey containing multiple-choice and open-ended questions was developed and disseminated online. Invitations to participate were delivered via e-mail listservs and through business cards provided at annual audiology conferences. All responses were anonymous at the time of data collection. Results Responses were collected from 209 participants. The majority of participants reported seeing at least one normal-hearing patient per month who reported significant communication difficulties. However, few respondents indicated that their location had specific protocols for the treatment of these patients. Counseling was reported as the most frequent rehabilitation method, but results revealed that audiologists across various work settings are also successfully starting to fit patients with mild-gain hearing aids. Responses indicated that patient compliance with computer-based auditory training methods was regarded as low, with patients generally preferring device-based rehabilitation options. Conclusions Results from this questionnaire survey strongly suggest that audiologists frequently see normal-hearing patients who report auditory difficulties, but that few clinicians are equipped with established protocols for diagnosis and management. While many feel that mild-gain hearing aids provide considerable benefit for these patients, very little research has been conducted to date to support the use of hearing aids or other rehabilitation options for this unique patient population. This study reveals the critical need for additional research to establish evidence-based practice guidelines that will empower clinicians to provide a high level of clinical care and effective rehabilitation strategies to these patients.

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