Discovering Unique, Low-Energy Transition States Using Evolutionary Molecular Memetic Computing

2013 ◽  
Vol 8 (3) ◽  
pp. 54-63 ◽  
Author(s):  
M. Ellabaan ◽  
Y.S. Ong ◽  
S.D. Handoko ◽  
C.K. Kwoh ◽  
H.Y. Man
Keyword(s):  
Transition States ◽  
Energy Transition ◽  
Low Energy ◽  
Memetic Computing

scholarly journals The Growth of InAsSb/InAs/InPSb/InAs Mid-Infrared Emitters by Metal-Organic Chemical Vapor Deposition

1999 ◽  
Vol 607 ◽  
Author(s):  
R. M. Biefeld ◽  
J. D. Phillips ◽  
S. R. Kurtz
Keyword(s):  
Chemical Vapor Deposition ◽  
Vapor Deposition ◽  
Chemical Vapor ◽  
Energy Transition ◽  
Low Energy ◽  
Organic Chemical ◽  
Mid Infrared ◽  
Metal Organic ◽  
Organic Chemical Vapor Deposition ◽  
Cladding Layers

AbstractWe report on the metal-organic chemical vapor deposition (MOCVD) of strained layer superlattices (SLSs) of InAsSb/InAs/InPSb/InAs as well as mid-infrared optically pumped lasers grown using a high speed rotating disk reactor (RDR). The devices contain AlAsSb cladding layers and strained, type I, InAsSb/InAs/InPSb/InAs strained layer superlattice (SLS) active regions. By changing the layer thickness and composition of the SLS, we have prepared structures with low temperature (<20K) photoluminescence wavelengths ranging from 3.4 to 4.8 µm. The optical properties of the InAsSb/InPSb superlattices revealed an anomalous low energy transition that can be assigned to an antimony-rich, interfacial layer in the superlattice. This low energy transition can be eliminated by introducing a 1.Onm InAs layer between the InAsSb and InPSb layers in the superlattice. An InAsSb/InAs/InPSb/InAs SLS laser was grown on an InAs substrate with AlAs0.16Sb0.844cladding layers. A lasing threshold and spectrally narrowed laser emission were seen from 80 through 250 K, the maximum temperature where lasing occurred. The temperature dependence of the SLS laser threshold is described by a characteristic temperature, T0 = 39 K, from 80 to 200 K.

Observing the base-by-base search for native structure along transition paths during the folding of single nucleic acid hairpins

2021 ◽  
Vol 118 (49) ◽  
pp. e2101006118
Author(s):  
Noel Q. Hoffer ◽  
Krishna Neupane ◽  
Michael T. Woodside
Keyword(s):  
Nucleic Acid ◽  
High Resolution ◽  
Optical Tweezers ◽  
Energy Landscape ◽  
Transition States ◽  
Energy Transition ◽  
High Energy ◽  
Sequence Dependence ◽  
High Energy Transition ◽  
Nucleotide Residue

Biomolecular folding involves searching among myriad possibilities for the native conformation, but the elementary steps expected from theory for this search have never been detected directly. We probed the dynamics of folding at high resolution using optical tweezers, measuring individual trajectories as nucleic acid hairpins passed through the high-energy transition states that dominate kinetics and define folding mechanisms. We observed brief but ubiquitous pauses in the transition states, with a dwell time distribution that matched microscopic theories of folding quantitatively. The sequence dependence suggested that pauses were dominated by microbarriers from nonnative conformations during the search by each nucleotide residue for the native base-pairing conformation. Furthermore, the pauses were position dependent, revealing subtle local variations in energy–landscape roughness and allowing the diffusion coefficient describing the microscopic dynamics within the barrier to be found without reconstructing the shape of the energy landscape. These results show how high-resolution measurements can elucidate key microscopic events during folding to test fundamental theories of folding.

scholarly journals Energy Efficiency Standards of Single-Family Houses: Factors in Homeowners’ Decision-Making in Two Austrian Regions

2015 ◽  
Vol 5 (2) ◽  
pp. 49 ◽  
Author(s):  
Katja Bedenik ◽  
Ralph Hansmann ◽  
Monika Popp ◽  
Anne Von Streit ◽  
Claudia R. Binder
Keyword(s):  
Energy Efficiency ◽  
Residential Buildings ◽  
Energy Transition ◽  
Low Energy ◽  
Building Energy Efficiency ◽  
Single Family ◽  
Building Projects ◽  
Federal States ◽  
Energy Efficiency Standard ◽  
Energy Efficiency Standards

<p>The energy efficiency of residential buildings is a central issue in the widely discussed energy transition. This study investigates which factors influence homeowners´ decisions regarding the energy efficiency standard of their houses. Homeowners who built or renovated their houses between 2008 and 2013 participated in a questionnaire survey in two Austrian “energy regions” within the federal states of Styria and Burgenland. In the majority (66%) of cases, homeowners chose the low-energy house standard B (≤ 50kWh/m<sup>2</sup>a) for their building or renovation projects, followed by the conventional standard C (≤ 100kWh/m<sup>2</sup>a) (21%). Only 13% realized ultra-low-energy, passive or plus-energy houses with a higher energy efficiency standard (A (≤ 25kWh/m<sup>2</sup>a), A+ (≤ 15kWh/m<sup>2</sup>a), or A++ (≤ 10kWh/m<sup>2</sup>a)). Expert recommendations on energy standards showed the highest correlation with the selected standards, and on average, new building projects realized better energy efficiency standards than did renovations. Further variables that were significantly related to the realized standards included homeowners’ attitudes and knowledge about building energy efficiency standards and the age of the respondents. Although the homeowners who were surveyed were initially satisfied with the selected energy efficiency standard, many now indicate a preference to implement significantly higher energy efficiency standards than those achieved in their project. Further, they would recommend even significantly higher energy efficiency standards to friends than the standards preferred for their own house. These findings suggest that current preferences and communication in social networks promote higher future energy efficiency standards.</p>

Effect of the metal matrix on the probability of the low-energy transition in 234Pa nuclei

2011 ◽  
Vol 53 (3) ◽  
pp. 225-228 ◽  
Author(s):  
A. A. Rimskii-Korsakov ◽  
V. V. Kol’tsov ◽  
V. V. Karasev
Keyword(s):  
Metal Matrix ◽  
Energy Transition ◽  
Low Energy

scholarly journals Guanidine-catalyzed asymmetric Strecker reaction: modes of activation and origin of stereoselectivity

2016 ◽  
Vol 94 (12) ◽  
pp. 1099-1108 ◽  
Author(s):  
Hansong Xue ◽  
Choon-Hong Tan ◽  
Ming Wah Wong
Keyword(s):  
Density Functional ◽  
Catalytic Mechanism ◽  
Interaction Analysis ◽  
Transition States ◽  
Enantiomeric Excess ◽  
Energy Transition ◽  
Density Functional Theory Calculations ◽  
Noncovalent Interaction ◽  
Acid Activation ◽  
Strecker Reaction

Density functional theory calculations were employed to study the catalytic mechanism, modes of activation, and origin of enantioselectivity of guanidine-catalyzed asymmetric Strecker reaction of N-benzhydryl imine with hydrogen cyanide. Two types of bifunctional activation mode were identified, namely conventional bifunctional Brønsted acid activation and unconventional bifunctional Brønsted–Lewis acid activation. The lowest-energy transition states correspond to the conventional bifunctional mode of activation. The calculated enantiomeric excess, based on eight lowest-energy C–C bond forming transition states, is in good accord with observed enantioselectivity. NCI (noncovalent interaction) analysis of the key transition states reveals extensive noncovalent interactions, including aromatic interactions and hydrogen bonds, between the guanidinium catalyst and substrates. Multiple aryl–aryl interactions between the phenyl groups of guanidine catalyst and the phenyl rings of N-benzhydryl imine are the key stabilizations in the most stable (R)-inducing transition state. Differential attractive aryl–aryl stabilization is the major factor for stereoinduction.

Sign in / Sign up

Export Citation Format

Share Document