Mass Modification Research Articles

Sea ice production and water mass modification in the eastern Laptev Sea

[1] A simple polynya flux model driven by standard atmospheric forcing is used to investigate the ice formation that took place during an exceptionally strong and consistent western New Siberian (WNS) polynya event in 2004 in the Laptev Sea. Whether formation rates are high enough to erode the stratification of the water column beneath is examined by adding the brine released during the 2004 polynya event to the average winter density stratification of the water body, preconditioned by summers with a cyclonic atmospheric forcing (comparatively weakly stratified water column). Beforehand, the model performance is tested through a simulation of a well-documented event in April 2008. Neglecting the replenishment of water masses by advection into the polynya area, we find the probability for the occurrence of density-driven convection down to the bottom to be low. Our findings can be explained by the distinct vertical density gradient that characterizes the area of the WNS polynya and the apparent lack of extreme events in the eastern Laptev Sea. The simple approach is expected to be sufficiently rigorous, since the simulated event is exceptionally strong and consistent, the ice production and salt rejection rates are likely to be overestimated, and the amount of salt rejected is distrusted over a comparatively weakly stratified water column. We conclude that the observed erosion of the halocline and formation of vertically mixed water layers during a WNS polynya event is therefore predominantly related to wind- and tidally driven turbulent mixing processes.

Significant in-mediumη′mass reduction insNN = 200 GeV Au+Au collisions at the BNL Relativistic Heavy Ion Collider

In high energy heavy ion collisions a hot and dense medium is formed, where the U_A(1) or chiral symmetry may temporarily be restored. As a consequence, the mass of the eta'(958) mesons may be reduced to its quark model value, and the abundance of eta' mesons at low p_T may be enhanced by more than a factor of 10. The intercept parameter lambda_* of the charged pion Bose--Einstein correlations provides a sensitive observable of the possibly enhanced eta' abundance. We have analyzed lambda_*(m_T) data from sqrt(s(NN))=200 GeV central Au+Au reactions measured at the BNL Relativistic Heavy Ion Collider (RHIC), using extensive Monte Carlo simulations based on six popular models for hadronic multiplicities. Based on the combined STAR and PHENIX data set, and on various systematic investigations of resonance multiplicities and model parameters, we conclude that in sqrt(s(NN))=200 GeV central Au+Au reactions the mass of the eta' meson is reduced by Delta m > 200 MeV, at the 99.9% confidence level in the considered model class. Such a significant eta' mass modification may indicate the restoration of the U_A(1) symmetry in a hot and dense hadronic matter and the return of the ninth "prodigal" Goldstone boson. A similar analysis of NA44 S+Pb data at top CERN Super Proton Synchrotron (SPS) energies showed no significant in-medium eta' mass modification.

Equatorward Pathways of Solomon Sea Water Masses and Their Modifications

Abstract The Solomon Sea is a key region of the southwest Pacific Ocean, connecting the thermocline subtropics to the equator via western boundary currents (WBCs). Modifications to water masses are thought to occur in this region because of the significant mixing induced by internal tides, eddies, and the WBCs. Despite their potential influence on the equatorial Pacific thermocline temperature and salinity and their related impact on the low-frequency modulation of El Niño–Southern Oscillation, modifications to water masses in the Solomon Sea have never been analyzed to our knowledge. A high-resolution model incorporating a tidal mixing parameterization was implemented to depict and analyze water mass modifications and the Solomon Sea pathways to the equator in a Lagrangian quantitative framework. The main routes from the Solomon Sea to the equatorial Pacific occur through the Vitiaz and Solomon straits, in the thermocline and intermediate layers, and mainly originate from the Solomon Sea south inflow and from the Solomon Strait itself. Water mass modifications in the model are characterized by a reduction of the vertical temperature and salinity gradients over the water column: the high salinity of upper thermocline water [Subtropical Mode Water (STMW)] is eroded and exported toward surface and deeper layers, whereas a downward heat transfer occurs over the water column. Consequently, the thermocline water temperature is cooled by 0.15°–0.3°C from the Solomon Sea inflows to the equatorward outflows. This temperature modification could weaken the STMW anomalies advected by the subtropical cell and thereby diminish the potential influence of these anomalies on the tropical climate. The Solomon Sea water mass modifications can be partially explained (≈60%) by strong diapycnal mixing in the Solomon Sea. As for STMW, about a third of this mixing is due to tidal mixing.

Structural parameter identification by use of additional known masses and its experimental application

SUMMARY In this study, a structural parameter identification method for damped structures is proposed. Modal identification is performed under several mass-modified conditions and structural parameters consistent with the identified modal parameters are determined. Its advantages as compared to other parameter identification methods are as follows. Initial guess of the system's structural parameters is unnecessary. Computational cost is low due to the algorithm's non-iterative calculation scheme. Furthermore, the proposed algorithm can detect not only a single damage, but also multiple damages without compromising the identification accuracy. First, the identification algorithm is theoretically developed. Modal parameter identification of a structure before and after the introduction of additional masses is conducted. By considering the relationship between the additional masses and modal properties before and after mass modification, structural parameters of a damped system, i.e. mass, stiffness and damping coefficient, are inversely identified from these modal parameters. The algorithm is subsequently validated through both numerical simulation and experiments on scale-models. The algorithm gives stable identification of structural parameters, provided all degrees of freedom of the system are observable. A mode selection indicator is also proposed. The effectiveness of this empirical indicator and the use of various mass-modified conditions in improving the robustness of the identification method are also numerically and experimentally confirmed. Finally, the proposed algorithm is extended to identify stiffness of beam models without utilizing rotational elements in mode shapes. Numerical simulation on a damaged beam model is performed, and its stiffness is identified. Copyright © 2011 John Wiley & Sons, Ltd.

Experimental validation of a new statistical process control feature for damage detection

A novel statistical process control-based method for damage detection in cantilever-like structures is presented in this paper . It is based on time-domain data obtained from the free vibrations of the first mode of the structure, measured at only one point. The concept of signal length is introduced here as a feature for statistical process control. A statistical model consistent with extreme value theory is fitted to the operational data and used to establish control limits. A strategy based on controlling runs is adopted to increase the sensitivity of the detection. The procedure was applied to a four-storey steel frame, which was subjected in turn to mass and stiffness modifications by adding masses or loosening bolts in a beam–column connection. The results were successful; the proposed procedure was able to detect an increase of 0.04% of the total mass of the frame and loosening of one out of 152 bolts.

DILEPTON PRODUCTION STUDIED WITH THE HADES SPECTROMETER

With the HADES spectrometer at GSI we have studied dilepton production in various collision systems from elementary N + N , over p + A , up to the medium-heavy Ar + KCl system. We have confirmed the puzzling results of the former DLS collaboration at the Bevalac. While we have traced the origin of the excess pair yield in C + C collisions to elementary p + p and n + p processes, we find a significant contribution from the dense phase of the collision in larger Ar + KCl system. From recently obtained e + e - pair spectra in p + p and p + Nb interactions at 3.5 GeV kinetic beam energy the inclusive production cross sections for neutral pions, η , ω and ρ mesons are extracted for the first time at this beam energy. Furthermore, the production mechanisms of the vector mesons, which are not known at these energies, are investigated. The direct comparison of p + p and p + Nb data allows us to investigate in-medium mass modifications of vector mesons at nuclear ground state density. On the other hand, exclusive production of ω and η mesons in p + p reactions at 3.5 GeV were studied via their π+π-π0 decay channel. Production cross sections and angular distributions for both states were determined.

Rapid changes of the ice mass configuration in the dynamic Diablotins ice cave – Fribourg Prealps, Switzerland

Abstract. The Gouffre des Diablotins is a deep cave system located in the Swiss Prealps. In 1991, the lower entrance zone of the cave was almost free of ice. Nevertheless the ice volume sharply increased in 1994, plugging almost totally the gallery from the lower entrance. The ice cave has also experienced a flood period between 1996 and 2007 and very heterogeneous ice surface morphologies and textures have formed. Continuous cave climate measurements initiated in 2009 showed the predominant role of winter atmospheric air conditions to drive both the efficiency of chimney-effect air circulation and seasonal modifications of the ice mass. The main part of the ice loss is currently due to sublimation in wintertime.

Indirect Observation of an In-Mediumη′Mass Reduction insNN=200 GeVAu+AuCollisions

PHENIX and STAR data on the intercept parameter of the two-pion Bose-Einstein correlation functions in sqrt(s_{NN}) = 200 GeV Au+Au collisions are analyzed in terms of different models of hadronic multiplicities. To describe this combined PHENIX and STAR dataset, an in-medium eta' mass reduction of at least 200 MeV is needed, at the 99.9 % confidence level in the considered model class. Such a significant eta' mass modification may indicate the restoration of the U_A(1) symmetry in a hot and dense hadronic matter and the return of the 9th "prodigal" Goldstone boson.

J/ψandηcmasses in isospin asymmetric hot nuclear matter: A QCD sum rule approach

We study the in-medium masses of the charmonium states $J/\ensuremath{\psi}$ and ${\ensuremath{\eta}}_{c}$ in the nuclear medium using the QCD sum rule approach. These mass modifications arise owing to modifications of the scalar and the twist-2 gluon condensates in the hot hadronic matter. The scalar gluon condensate $\ensuremath{\langle}\frac{{\ensuremath{\alpha}}_{s}}{\ensuremath{\pi}}{G}_{\ensuremath{\mu}\ensuremath{\nu}}^{a}{{G}^{a}}^{\ensuremath{\mu}\ensuremath{\nu}}\ensuremath{\rangle}$ and the twist-2 tensorial gluon operator $\ensuremath{\langle}\frac{{\ensuremath{\alpha}}_{s}}{\ensuremath{\pi}}{G}_{\ensuremath{\mu}\ensuremath{\sigma}}^{a}{{{G}^{a}}_{\ensuremath{\nu}}}^{\ensuremath{\sigma}}\ensuremath{\rangle}$ in the nuclear medium are calculated from the medium modification of a scalar dilaton field introduced to incorporate trace anomalies of QCD within the chiral SU(3) model used in the present investigation. The effects of isospin asymmetry, density, and temperature of the nuclear medium on the in-medium masses of the lowest charmonium states $J/\ensuremath{\psi}$ and ${\ensuremath{\eta}}_{c}$ mesons are investigated in the present work. The results of the present investigation are compared with the existing results on the masses of these states. The medium modifications of the masses of these charmonium states ($J/\ensuremath{\psi}$ and ${\ensuremath{\eta}}_{c}$) seem to be appreciable at high densities and should modify the experimental observables arising from the compressed baryonic matter produced in asymmetric heavy-ion collision experiments at the future facility of Facility for Antiproton and Ion Research, GSI.

K−absorption at rest in nuclei followed bypΛemission

$p\,\Lambda$ emission in coincidence following $K^-$ absorption at rest in nuclei is studied using quantum mechanical scattering theory and nuclear wave functions. $K^-$ absorption is assumed to occur on two protons in the nucleus. In the formalism, emphasis is put on the study of the final state interaction (FSI) effects of $p$ and $\Lambda$ with the recoiling nucleus. We include elastic scattering and single nucleon knock-out (KO) channels in the FSI. Calculations are presented for the $^{12}$C nucleus, using shell model wave functions, and without any extra mass modification of the $K^-\,pp$ system in the nucleus. Calculated results are presented for the angular correlation distribution between $p$ and $\Lambda$, their invariant mass distribution and the momentum spectra of $p$ and $\Lambda$. These results are compared with the corresponding experimental measurements \cite{agnello}. With only elastic scattering FSI included, the angular correlation distribution and the momentum spectra are found to be in good accord with the corresponding measurements. With full FSI the calculated $p\,\Lambda$ invariant mass distribution is found to have two peaks, one corresponding to the elastic scattering FSI and another to single nucleon KO FSI. The KO peak agrees fully, in position and shape, with the peak observed in Ref. \cite{agnello}. The peak corresponding to elastic scattering FSI does not seem to exist in the measured distribution. Considering that such a two peak structure is always seen in the inclusive ($p$, $p^\prime $) and ($e$, $e^\prime $) reactions in nuclei at intermediate energies, absence of the elastic scattering peak in the $p\,\Lambda$ reaction is intriguing.

A model-free method for identification of mass modifications

SUMMARY In this paper, a model-free methodology for off-line identification of modifications of structural mass is proposed and verified experimentally. The methodology of the virtual distortion method is used: the modifications are modeled by the equivalent pseudo-loads that act in the related degrees of freedom of the unmodified structure; their influence on the response is computed using a convolution of the pseudo-loads with the experimentally obtained local impulse responses. As a result, experimentally measured data are directly used to model the response of the modified structure in a non-parametric way. The approach obviates the need for a parametric numerical model of the structure and for laborious initial updating of its parameters. Moreover, no topological information about the structure is required, besides potential locations of the modifications. The identification is stated as a problem of minimization of the discrepancy between the measured and the modeled responses of the modified structure. The formulation allows the adjoint variable method to be used for a quick first- and second-order sensitivity analysis, so that Hessian-based optimization algorithms can be used for fast convergence. The proposed methodology was experimentally verified using a 3D truss structure with 70 elements. Mass modifications in a single node and in two nodes were considered. Given the initially measured local impulse responses, a single sensor and single excitation were sufficient for the identification. Copyright © 2010 John Wiley & Sons, Ltd.

A development of HBD for the J-PARC E16 experiment

Spontaneous breaking of the chiral symmetry is considered to be the origin of hadron mass. The chiral symmetry is expected to be (partially) restored in finite density and the hadron mass is predicted to decrease, even at the normal nuclear density. The J-PARC E16 experiment was proposed to investigate the origin of the mass through the mass modification of vector mesons in a finite density environment. The masses of vector mesons, which are produced in p+A reactions, are measured through the electron–positron decays. A Cherenkov detector with a large acceptance and with fine segmentations is required for the electron identification. HBD is ideal for the purpose; it is a mirror-less, windowless Cherenkov detector with a stack of Gas Electron Multipliers (GEMs) on top of which CsI is evaporated. CF 4 acts as amplification gas and as Cherenkov radiator. We have developed a prototype of HBD for the J-PARC E16 experiment. It is constructed with two layers of Liquid-Crystal-Polymer (LCP) GEMs with a thickness of 100 μ m each, on the uppermost surface CsI is evaporated. The use of thicker GEMs leads to a larger gain at the first stage and to tolerance to sparks, compared to regular 50 μ m Kapton-GEMs. With a threshold at ∼ 16 electrons, a pion rejection factor of 100 can be achieved, which is required for the E16 experiment. A beam test was performed with a positron beam and the prototype successfully detected the Cherenkov radiation. The number of photoelectrons observed was about 5–6. Although these results were not satisfactory to reach a pion rejection factor of 100 with a reasonable efficiency at this point, improvements towards the goal are expected from photocathode and gas purity.

Mass modification of itinerant carriers in RKKY oscillations induced by finite-range exchange interactions

We investigate the Ruderman-Kittel-Kasuya-Yosida oscillations of the itinerant carrier spin density in a system where those oscillations appear only due to a finite distribution of a localized spin. The system represents a half-infinite one-dimensional quantum wire with a magnetic impurity located at its edge. In contrast to the conventional model of a pointlike exchange interaction the itinerant carrier spin-density oscillations in this system exist. We analytically demonstrate that when the radius of the exchange interaction is less than the wavelength of the itinerant carriers living on the Fermi surface, the long-range behavior of the oscillations is identical to the one taking place in the zero-radius limit of the same exchange interaction but for an infinite one-dimensional quantum wire where, in comparison with the original half-infinite system, the mass of the itinerant carriers is strongly modified by the exchange interaction radius. On the basis of our analysis we make a suggestion on directionality of surface Ruderman-Kittel-Kasuya-Yosida interaction shown in recent experiments: we believe that in general the anisotropy of the Ruderman-Kittel-Kasuya-Yosida interaction could result not only from the anisotropy of the Fermi surface of itinerant carriers but also from the anisotropy of the spin carrying atomic orbitals of magnetic impurities.

Dmesons and charmonium states in asymmetric nuclear matter at finite temperatures

We investigate the in-medium masses of $D$ and $\mathrm{D\ifmmode \bar{}\else \={}\fi{}}$ mesons in the isospin-asymmetric nuclear matter at finite temperatures arising due to the interactions with the nucleons, the scalar-isoscalar meson $\ensuremath{\sigma}$, and the scalar-isovector meson $\ensuremath{\delta}$ within a SU(4) model. However, since the chiral symmetry is explicitly broken for the SU(4) case due to the large charm quark mass, we use the SU(4) symmetry here only to obtain the interactions of the $D$ and $\mathrm{D\ifmmode \bar{}\else \={}\fi{}}$ mesons with the light hadron sector but use the observed values of the heavy hadron masses and empirical values of the decay constants. The in-medium masses of $J/\ensuremath{\psi}$ and the excited charmonium states [$\ensuremath{\psi}(3686)$ and $\ensuremath{\psi}(3770)$] are also calculated in the hot isospin-asymmetric nuclear matter in the present investigation. These mass modifications arise due to the interaction of the charmonium states with the gluon condensates of QCD, simulated by a scalar dilaton field introduced to incorporate the broken scale invariance of QCD within the effective chiral model. The change in the mass of $J/\ensuremath{\psi}$ in the nuclear matter with the density is seen to be rather small, as has been shown in the literature by using various approaches, whereas the masses of the excited states of charmonium [$\ensuremath{\psi}(3686)$ and $\ensuremath{\psi}(3770)$] are seen to have considerable drop at high densities. The present study of the in-medium masses of $D$ ($\mathrm{D\ifmmode \bar{}\else \={}\fi{}}$) mesons as well as of the charmonium states will be of relevance for the observables from the compressed baryonic matter, like the production and collective flow of the $D$ ($\mathrm{D\ifmmode \bar{}\else \={}\fi{}}$) mesons, resulting from the asymmetric heavy-ion collision experiments planned at the future facility of the GSI Facility for Antiproton and Ion Research. The mass modifications of $D$ and $\mathrm{D\ifmmode \bar{}\else \={}\fi{}}$ mesons as well as of the charmonium states in hot nuclear medium can modify the decay of the charmonium states (${\ensuremath{\Psi}}^{\ensuremath{'}},{\ensuremath{\chi}}_{c},J/\ensuremath{\Psi}$) to $D\mathrm{D\ifmmode \bar{}\else \={}\fi{}}$ pairs in the hot dense hadronic matter. The small attractive potentials observed for the $\mathrm{D\ifmmode \bar{}\else \={}\fi{}}$ mesons may lead to formation of the $\mathrm{D\ifmmode \bar{}\else \={}\fi{}}$ mesic nuclei.

Circulation and Water Mass Modification in the Brazil–Malvinas Confluence

Abstract The confluence between the Brazil Current and the Malvinas Current [the Brazil–Malvinas Confluence (BMC)] in the Argentine Basin is characterized by a complicated thermohaline structure favoring the exchanges of mass, heat, and salt between the subtropical gyre and the Antarctic Circumpolar Current (ACC). Analysis of thermohaline properties of hydrographic sections in the BMC reveals strong interactions between the ACC and subtropical fronts. In the Subantarctic Front, Subantarctic Mode Water (SAMW), Antarctic Intermediate Water (AAIW), and Circumpolar Deep Water (CDW) warm (become saltier) by 0.4° (0.08), 0.3° (0.02), and 0.6°C (0.1), respectively. In the subtropical gyre, AAIW and North Atlantic Deep Water have cooled (freshened) by 0.4° (0.07) and 0.7°C (0.11), respectively. To quantify those ACC–subtropical gyre interactions, a box inverse model surrounding the confluence is built. The model diagnoses a subduction of 16 ± 4 Sv (1 Sv ≡ 106 m3 s−1) of newly formed SAMW and AAIW under the subtropical gyre corresponding to about half of the total subduction rate of the South Atlantic found in previous studies. Cross-frontal heat (0.06 PW) and salt (2.4 × 1012 kg s−1) gains by the ACC in the BMC contribute to the meridional poleward heat and salt fluxes across the ACC. These estimates correspond to perhaps half of the total cross-ACC poleward heat flux. The authors’ results highlight the BMC as a key region in the subtropical–ACC exchanges.

A Proteome-wide Analysis of Kinase-Substrate Network in the DNA Damage Response

The DNA damage checkpoint, consisting of an evolutionarily conserved protein kinase cascade, controls the DNA damage response in eukaryotes. Knowledge of the in vivo substrates of the checkpoint kinases is essential toward understanding their functions. Here we used quantitative mass spectrometry to identify 53 new and 34 previously known targets of Mec1/Tel1, Rad53, and Dun1 in Saccharomyces cerevisiae. Analysis of replication protein A (RPA)-associated proteins reveals extensive physical interactions between RPA-associated proteins and Mec1/Tel1-specific substrates. Among them, multiple subunits of the chromatin remodeling complexes including ISW1, ISW2, INO80, SWR1, RSC, and SWI/SNF are identified and they undergo DNA damage-induced phosphorylation by Mec1 and Tel1. Taken together, this study greatly expands the existing knowledge of the targets of DNA damage checkpoint kinases and provides insights into the role of RPA-associated chromatins in mediating Mec1 and Tel1 substrate phosphorylation in vivo.

Wintertime mixed layer measurements at Maud Rise, Weddell Sea

Sea ice plays a crucial role in the exchange of heat between the ocean and the atmosphere, and areas of intense air‐sea‐ice interaction are important sites for water mass modification. The Weddell Sea is one of these sites where a relatively thin first‐year ice cover is constantly being changed by mixing of heat from below and stress exerted from the rapidly changing and intense winds. This study presents mixed layer turbulence measurements obtained during two wintertime drift stations in August 2005 in the eastern Weddell Sea, close to the Maud Rise seamount. Turbulence in the boundary layer is found to be controlled by the drifting ice. Directly measured heat fluxes compare well with previous studies and are well estimated from the mixed layer temperatures and mixing. Heat fluxes are also found to roughly balance the conductive heat flux in the ice; hence, little freezing/melting was observed. The under‐ice topography is estimated to be hydraulically very smooth; comparison with a steady 1‐D model shows that these estimates are made too close to the ice‐ocean interface to be representative for the entire ice floe. The main source and sink of turbulent kinetic energy are shear production and dissipation. Observations indicate that the dynamics of the under‐ice boundary layer are influenced by a horizontal variability in mixed layer density and an increasing amount of open leads in the area.

Study of in-medium ω-meson properties in Ap and pA collisions

We propose to investigate the in-medium properties of vector $\omega$ mesons at the normal nuclear density in Ap(pA) collisions and at higher density in AA collisions at the ITEP accelerator facility TWAC. Using of the inverse Ap kinematics will permit us to study the $\omega$ meson production in a wide momentum interval included the not yet explored range of small meson momenta relative to the projectile nuclei where the mass modification effect in nuclear matter is expected to be the strongest. Momentum dependence of the in-medium $\omega$ meson width will be studied in the traditional pA kinematics. We intend to use the electromagnetic calorimeter for reconstruction of the $\omega$ meson invariant mass by detecting photons from the $\omega \to \pi^{0}\gamma \to 3\gamma$ decay. The model calculations and simulations with RQMD generator show feasibility of the proposed experiment. Available now intensity of the ion beams provides a possibility to collect large statistics and make decisive conclusion about the $\omega$ meson properties at density of normal nuclei. At the second stage of the investigation the $\omega$ meson properties will be studied in AA collisions at higher density. Interpretation of these measurements will be based on the results obtained in Ap(pA) interactions. Further investigation of the in-medium properties of light unflavored and charmed mesons can be performed at ITEP and at GSI(FAIR) where higher ion energies will be accessible in near future.

The effects of mixing and spreading on density in near-field river plumes

Abstract Water mass modification in surface-trapped, near-field river plumes is examined using a 1.5-layer reduced gravity model and a three-dimensional numerical model. Solutions to the layer model are shown to be qualitatively similar to previous observations and three-dimensional simulations of near-field plumes. Analytic analysis of the layer model demonstrates how the near-field plume is controlled by the competing processes of mixing and spreading. The two models are then used to explore the parameter space dependence of density changes within the near-field plume and their associated cross-shore length scales. Both the magnitude of density changes and their length scales are proportional to either estuarine discharge or fresh water discharge; density changes are also inversely proportional to the estuary mouth width. One surprising feature of the parameter space solutions is that the density of water exiting the near-field plume, a measure of the net dilution of the entire near-field plume, is shown to be inversely proportional to local mixing rates. This is because when local mixing is lower, the influence of plume spreading becomes greater; this spreading accelerates the plume, requiring more net mixing to bring the plume back to subcritical flow.

Electron subband structure in strained silicon UTB films from the Hensel–Hasegawa–Nakayama model – Part 1 analytical consideration and strain-induced valley splitting

Multi-gate FinFETs and ultra-thin silicon body SOI FETs are considered as perfect candidates for future technology nodes. Strong size quantization leads to a formation of quasi-two-dimensional subbands in carrier systems within thin silicon films. The employed Hensel–Hasegawa–Nakayama k·p Hamiltonian accurately describes the bulk structure up to the energies of 0.5–0.8eV and includes a shear strain component. Shear strain is responsible for effective mass modification and is therefore an important source of the electron mobility enhancement in ultra-thin silicon films. The influence of shear strain on the subband structure in thin silicon films is investigated.