envelope function
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2021 ◽  
Author(s):  
Vincent Casey ◽  
Alison Perry ◽  
Richard Conway

Abstract Purpose: The primary goal of this study was to establish a normative data set representing intraoral time series swallow pressure profiles for healthy adults using a novel wearable intraoral pressure sensing system, OroPress, developed to help with dysphagia (swallow disorder) clinical screening. Methods: Swallow intraoral pressure-time profiles for 35 healthy adults (17 male, 18 female) swallowing water (3 × 5cm3 ; 3 × 10cm3 ) and custard (3 × 5cm3 ) boluses (N = 9 × 35 = 315) were recorded using OroPress. Results: General swallow profile traits are identified to characterise an effective, efficient swallow. A profile-specific swallow envelope function is devised which in combination with profile metrics, provides a simple means of categorizing swallows as effective or impaired. Conclusion: The swallow profile data trace with superimposed and colour coded peaks, envelope function and related swallow metrics provides a simple human readable graphic to aid the real-time instrumented identification of subjects warranting more in-depth clinical assessment. It may also prove useful in the selection of training set profiles for machine learning and other analysis tools which could improve the discriminatory capabilities of intraoral pressure measurement in dysphagia diagnostics.


mBio ◽  
2021 ◽  
Author(s):  
Rhys Grinter ◽  
Faye C. Morris ◽  
Rhys A. Dunstan ◽  
Pok Man Leung ◽  
Ashleigh Kropp ◽  
...  

The pathogen Acinetobacter baumannii is considered an urgent threat to human health. A. baumannii is highly resistant to treatment with antibiotics, in part due to its protective cell envelope. This bacterium is only distantly related to other bacterial pathogens, so its cell envelope has distinct properties and contains components distinct from those of other bacteria that support its function.


Author(s):  
А.А. Ревин ◽  
А.М. Михайлова ◽  
А.А. Конаков ◽  
В.В. Цыпленков ◽  
В.Н. Шастин

In the framework of the envelope function approximation, the wave functions of electrons localized at shallow donors P, As, Sb in Ge are calculated taking into account the valley-orbit coupling caused by the donor short-range potential. It is proposed an approach that makes it possible to include inter-valley mixing in the equation for a multi-component envelope function. The calculation of the effects of the valley-orbit interaction was carried out according to the perturbation theory, while the "bare" single-valley functions were found using the Ritz method. The parameters of the short-range part of the potential and the coefficient of inter-valley mixing were found individually for each donor, making it possible to obtain the best agreement with the results of experimental measurements of the energies of the singlet and triplet states. The envelope functions of the 1s(A1) and 1s(T2) states are calculated. The parameters of the valley-orbit interaction are found for each donor. It is also shown how the functions of the excited 2s, 2p0, 2p±, 3p0 states should be modified in order to remain orthogonal to the singlet and triplet functions within the framework of a more rigorous multivalley model.


Author(s):  
Vurgaftman Igor

The chapter shows how the bulk theory described in Part I can be generalized within the envelope-function framework to model the band structure of layered materials with quantum confinement of carriers such as quantum wells or superlattices. In practice, the approach amounts to substituting derivatives for wavevector components in suitably chosen Hamiltonians as well as augmenting them with interface terms. It also discusses the spin splitting of the states of the quantum structures that arises from structural and intrinsic asymmetries.


2020 ◽  
pp. 649-698
Author(s):  
Sandip Tiwari

This chapter brings together several themes and perspectives by exploring them in quantum-confined conditions or in monolayer crystals. In it, confinement of electrons and holes at heterostructure interfaces, in inversion layers, in quantum wells and in superlattices is analyzed using the envelope function to illustrate the variety of interactions that must be properly accounted for. The formation of subbands in confinement, minibands in superlattices, and transmission, reflection and resonance at confined barriers and wells is discussed. Propagation, screening, scattering and the behavior of shallow dopants are discussed to illustrate changes with reduction of dimensions. Particular emphasis is placed on optical transitions to illustrate the changes in selection rules for interband and intraband transitions. Confined semiconductors are contrasted with monolayer semiconductors, using graphene and nanotubes as examples whose analysis and electronic properties are discussed, to compare them with the semiconductor discussions in earlier chapters.


2020 ◽  
Vol 102 (7) ◽  
Author(s):  
Pericles Philippopoulos ◽  
Stefano Chesi ◽  
Dimitrie Culcer ◽  
W. A. Coish

Author(s):  
А.А. Ревин ◽  
А.М. Михайлова ◽  
А.А. Конаков ◽  
В.Н. Шастин

In the framework of the envelope function approximation, the wave functions of low-lying 1s(A1), 2s, 2p0, 2p±, 3p0 states of shallow donor centers P, As, Sb in germanium are calculated considering the short-range part of the impurity potential. The latter is constructed individually for each impurity, taking into account the spatial dispersion of the dielectric function and the difference between the ionic cores of germanium and the impurity center. The envelope function equation was solved using the Ritz variational method, and selected trial wave functions of the orbitally non-degenerate s-states are characterized by two spatial scales: the first one is of the order of the donor effective Bohr radius and corresponds to the long-range part of the potential, and the second one, which is an order of magnitude less, simulates the electron response to the short-range part of the donor potential. The electron density in the donor ground state is shifted to the nucleus due to the attractive “central cell” correction. The envelope functions of p-states, in turn, are constructed in such a way they are orthogonal to the ground state envelope functions for each impurity center, and, unlike previous works, are different for various donors.


2019 ◽  
Vol 12 (1) ◽  
Author(s):  
Evelyn Ngwa Lumngwena ◽  
Liliwe Shuping ◽  
Netanya Bernitz ◽  
Zenda Woodman

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