Search

Propeller perforator flaps (PPFs) have long been proven as valid reconstructive tools for a wide range of soft tissue defects in different body regions. During the last decade, despite their numerous advantages, many authors have thoroughly analyzed outcomes of these flaps, sometimes discouraging their use mainly because of a high failure rate. Accurate patient selection, adequate preoperative planning, and an appropriate dissection technique seem to potentially improve outcomes. Our study provides a review of the relevant literature related to PPF complications and of our experience, describing reasons for failure, measures for preventing them, and approaches for a prompt evaluation and management of complications.

Reconstruction after resection of advanced stage hidradenitis suppurativa is currently performed with pedicled perforator flaps, that allow functional reconstruction and preservation of shoulder function. Skin availability is limited by the possibility of closing the donor site primarily. Bilateral cases need to be treated in two stages, since the operation is carried out in the lateral decubitus. In this manuscript the application of bilateral and bipedicled DIEAP flaps to bilateral and extensive cases is presented.Between October 2008 and October 2018, 39 patients were treated for axillary hidradenitis suppurativa. Of these, 11 patients had bilateral reconstruction with bilateral DIEAP flaps (22 flaps) and one patient had unilateral reconstruction with a bipedicled DIEAP flap. 23 flaps were used. Twelve flaps were raised above Scarpa's fascia, 6 flaps werethinned after dissection. Three flaps were not thinned in the first stage. Average flap size was 14 × 17cm for the bilateral flaps, while the bipedicled flap was 15 × 32cm.Average operative time was 324 minutes. No flap necrosis was observed. Two patients had wound dehiscences in the axilla and one in the abdomen, all treated conservatively. One patient had a pyoderma gangrenosum at both surgical sites that healed after cortisone therapy. No revisions were needed for the flaps that were thinned during the primary operation. The three patients whose flaps where not thinned needed liposuction after three months for thinning. There was one disease recurrence, unilateral and treated surgically. Mean follow up was 64 months.Axillary reconstruction with the DIEAP flap allows reconstruction of large and bilateral defect in a single operation closing the donor site primarily. If the flap is thinned during the operation, no thinning seems to be needed postoperatively. Otherwise the flap shall be thinned by liposuction three months after the initial procedure. We believe that the benefits of this technique outweigh the added complexity of a microsurgical procedure when bilateral resections are needed, the defects are too wide to close the donor site of a pedicled flap primarily and the lower abdomen is free of disease.EINFüHRUNG: Die Rekonstruktion der Axilla nach Resektion bei fortgeschrittener Hidradenitis suppurativa (Akne inversa) erfolgt in unserer Erfahrung mit gestielten Perforans-Lappenplastiken, die eine funktionelle Rekonstruktion und einen Funktionserhalt der Schulter erlauben. Die Verfügbarkeit der Haut ist um die Axilla durch die Notwendigkeit eines primären Verschlusses der Entnahmestelle begrenzt. In dieser Arbeit werden die Anwendung und die Ergebnisse von bilateralen freien DIEP-Lappenplastiken bei Patienten mit bilateraler und großflächiger Resektion vorgestellt. Von Oktober 2008 bis Oktober 2018 wurden 39 Patienten mit Hidradenitis suppurativa chirurgisch behandelt. Bei 11 dieser Patienten erfolgte eine bilaterale Rekonstruktion mit bilateraler DIEP-Lappenplastik (22 Lappenplastiken). Bei einem Patienten wurde eine unilaterale Rekonstruktion mithilfe einer doppelt gestielten DIEP-Lappenplastik durchgeführt. Insgesamt wurden 23 Lappenpkastiken verwendet. Zwölf Lappenplastiken wurden über der Scarpa-Faszie gehoben, 6 Lappenplastiken wurden nach der Dissektion ausgedünnt. Drei Lappenplastiken wurden in der ersten Phase nicht ausgedünnt. Die durchschnittliche Lappengröße betrug bei den bilateralen Lappenplastiken 14 × 17 cm und beim doppelt gestielten Lappenplastiken 15 × 32 cm. Die mittlere Nachbeobachtungszeit lag bei 64 Monaten. Die durchschnittliche Operationsdauer lag bei 324 Minuten. Es wurden keine Lappennekrosen festgestellt. In zwei Fällen kam es zu einer axillären, in einem Fall zu einer abdominalen Wunddehiszenz. Diese wurden alle konservativ behandelt. Bei einem Patienten wurde an beiden Operationsstellen ein Pyoderma gangraenosum beobachtet, das nach Kortisontherapie abheilte. Bei den Lappenplastiken, die während des primären Eingriffs ausgedünnt wurden, war keine Revision erforderlich. Die drei Patienten mit den nicht ausgedünnten Lappen benötigten nach drei Monaten eine Liposuktion zur Ausdünnung. In einem Fall kam es zu einem Krankheitsrezidiv. Dieses war unilateral und wurde chirurgisch behandelt. Die Rekonstruktion der Axilla mit DIEP-Lappenplastiken ermöglicht die Rekonstruktion großer und bilateraler Defekte in einem einzigen Eingriff mit primärem Verschluss der Entnahmestelle. Wenn die Lappenplastik während der Operation ausgedünnt wird, scheint postoperativ keine weitere Ausdünnung erforderlich zu sein. Ansonsten sollte der Lappen drei Monate nach dem Ersteingriff durch Liposuktion ausgedünnt werden.

Foundations of the theory of Coulomb drag of ballistic electrons of a quantum nanowire by a flux of monoenergetic heavy ions moving with the same velocity V have been elaborated. The ratio of the drag current to the initial current of the ionic beam has been determined. It has been shown that the drag current is a nonmonotonic function of the velocity V. This function has a sharp maximum at the velocity V = vnF/2, where n is the number of the upper active (i.e., participating in the charge transfer) electron miniband (channel) and vnF is the corresponding Fermi velocity. Thus, it turns out that the phenomenon of giant oscillations of the Coulomb drag current can be used for studying the electron spectra of ballistic nanostructures.

The problem of treating tissue defects of the scalp to date remains one of the actual problems of modern medicine. Low elasticity, stiffness, and the presence of hair follicles and skin deficit dictate the need for new treatments, cosmetic relevant requirements of this zone. The use of expander dermotension in recent years has found its wide distribution in the treatment of defects and deformities of covering tissue anywhere on the body. On the example of a patient K.32 years old hospitalized with diagnosis-basal cell epithelioma of the scalp-the defect of soft tissues, we demonstrated the use of expander plastic in the treatment of defect covering tissues of the scalp. Thus, when there is a defect or deformation of covering tissues of the scalp, the most optimal is defect removal by tissues expander plastic. Transposition of pre fabricated by dermotension tissue complexes allows to liquidate quickly the defect of soft tissues, restoring normal full layered structure of the affected area of the scalp, and get good aesthetic results of treatment in these patients.

The generation of the Joule heat upon collisionless passage of the direct and alternating electric currents in semiconductor quantum wires connecting two classical reservoirs has been discussed. The transverse dimension of the quantum wire is of the order of the de Broglie wavelength of conduction electrons. The spatial distribution of the Joule heat has been considered. The heat is released in the reservoirs at a distance of the electron mean free path. The total production of the Joule heat has been found to be identical in both reservoirs.

Here we develop a mathematical apparatus to describe quasi-classical fluctuations in a non-equilibrium electron gas with electron-electron collisions. We substantiate the method by deriving, from general principles of quantum kinetics, an equation recently proposed by us for an equal-time electron-electron correlation function. The derivation is performed using the kinetic diagram technique. In degenerate non-equilibrium gas, the theory predicts that there exists a specific equal-time correlation between electrons. Due to the prevalence of small-angle electron-electron scattering, the equation in question takes a rather simple and treatable form (the Coulomb-type electron-electron interaction stands out against the background of all other types of interaction as one that does not generate, in the framework of quasi-classical approach, any direct exchange effects).

The splitting of electronic levels in quantum wells of semimagnetic semiconductors typically characterized by large effective g factors is analyzed theoretically. They are found to be capable of supporting resonance, provided the Zeeman spin-level splitting is equal to the energy of the longitudinal optical phonon ħω‖. The resonance condition can be written as ħω‖ = gμBB. This condition can be satisfied by choosing the magnetic field Bsuch that the sum of the energies of the lowest spin level and the optical phonon coincides with the energy of the highest level. It is shown that these two degenerate energy levels should experience mutual repulsion. The magnitude of the corresponding splitting depends on both the electron-phonon and spin-orbit interactions in semiconductors; moreover, it turns out substantially lower than the Zeeman energy gμBB. Resonant passage of light through and its reflection from a quantum well are considered as one of possible ways to observe this energy level splitting.

The Joule heat generation in a quantum semiconductor nanowire joining two classical reservoirs is considered. We assume that the conductance of the system is determined by the phonon-assisted ballistic resistance. The spatial distribution of the generated heat is analysed. The heat generated within the nanostructure is determined. It is simply related to the phonon-assisted variation ΔG of the conductance. For a fixed voltage, the corresponding variation of the overall heat generation is negative and is determined by ΔG. Due to the same interaction the reduction of the heat generated in each reservoir is the same as the heat generated in the nanostructure. In other words, the presence of collisions within a nanowire does not violate the equality of the heat release in the reservoirs that are connected by the nanowire, although the rates and mechanisms of relaxation there may be different. We come to the conclusion that further investigation of various situations where the nanostructures are involved is needed to gain understanding as to why in some cases different heat generation in the two reservoirs is observed and predicted.

The influence of a longitudinal magnetic field on the Coulomb drag current created in the ballistic transport regime in a quantum well by a ballistic current in a nearby parallel quantum well is investigated. We consider the case where the magnetic field is so strong that the Larmour radius is smaller than the width of the well. Both in Ohmic and non-Ohmic case, sharp oscillations of the drag current as a function of the gate voltage or chemical potential are predicted. We also study dependence of the drag current on the voltage $V$ across the driving wire, as well as on the magnetic field $B$. Studying the Coulomb drag one can make conclusions about the electron spectrum and and electron-electron interaction in quantum wells., 11 pages, 2 figures

Drag of electrons of 1D ballistic nanowire by a nearby 1D beam of ions is considered. We assume that the ion beam is represented by an ensemble of heavy ions of the same velocity $\bf V$. The ratio of the drag current to primary current carried by the ion beam is calculated. The drag current appears to be a nonmonotonic function of velocity $V$, it has maxima for $V$ near $v_{nF}/2$ where $n$ is the number of electron miniband (channel) and $v_{nF}$ is the corresponding Fermi velocity. This means that the ion beam drag can be applied for ballistic nanostructure spectroscopy., 12 pages, 2 figures

Background: To provide quantitative objective data demonstrating the longevity and amount of volume augmentation in the fatty dystrophy of the facial tissue obtained with autologous lipofilling. Methods: In our clinic had been operated 8 patients for last 2 years with fatty dystrophy of the facial tissue. A prospective analysis of all patients who underwent at our private practice and were followed up for at least 1,5 year. Surgery was performed under general anesthesia it is necessary for clear results tissue correction. We based on the literature has seen numerous clinical reports highlighting the benefits of autologous fat transfer for face from that areas, fat was collected from the abdomen (most frequently used donor site), hips, outer thighs (saddle-bags), internal knee or thigh, with quantitative volume measurements evaluating the amount of postoperative volume change. Results: Twenty eight patients were included in the study. The mean follow-up time was 18 months. The mean amount of autologous fat injected into each face region was 10-70 mL. Hypercorrection was performed after 3 months and it was 20-50% of the initial injected fat volume. Overall, the mean absolute volume augmentation measured at their last (after 6 month) post operative visit was 10-25%. There was variability between patients in the volume amount and percentage that remained. The resorption process was observed in two patients after 6 month. We made correction with hyaluronic acid and silicone implants. Conclusion: To our knowledge, this study is the first clinical quantification in our practise of autologous fat transfer and/or grafting in the literature that provides definitive evidence on the amount as well as the resultant longevity in the face. Autologous fat transfer to the face has definite long-term volume augmentation results. On average, approximately 25-35% of the injected volume remains at 18 months. However, some variability exists in the percentage of volume that remains that may require a touch-up procedure.

We work out a theory of shot noise in a special case. This is a noise of the Coulomb drag current excited under the ballistic transport regime in a one-dimensional nanowire by a ballistic non-Ohmic current in a nearby parallel nanowire. We predict sharp oscillation of the noise power as a function of gate voltage or the chemical potential of electrons. We also study dependence of the noise on the voltage V across the driving wire. For relatively large values of V the noise power is proportional to V^2., Comment: 9 pages, 2 figures

We investigate a mechanism responsible for the observed very short times of the photon-echo decay (of the order of a few femtoseconds) in semiconductors. It is associated with the loss of phase memory as a result of the interaction of the interband mixed state with an unscreened random Coulomb potential of the photocarriers and/or charged impurities. A time characteristic of a system of interacting electrons is found. This is the time of phase breaking ${\mathrm{\ensuremath{\tau}}}_{\mathit{c}\mathit{p}\mathit{h}\mathit{i}}$, which we calculate within the eikonal approximation using diagrammatic techniques. ${\mathrm{\ensuremath{\tau}}}_{\mathit{c}\mathit{p}\mathit{h}\mathit{i}}$ is shown to be typically much shorter than both the time of electron-electron collisions and the period of plasma oscillations. We demonstrate that the screening of Coulomb potential cannot be built up during this time. ${\mathrm{\ensuremath{\tau}}}_{\mathit{c}\mathit{p}\mathit{h}\mathit{i}}$ is proportional to ${\mathit{n}}^{\mathrm{\ensuremath{-}}1/\mathit{d}}$ (where n is the carrier concentration and d the dimensionality of a system), which is consistent with the experimental results. The derived law of echo decay of the form exp[-(\ensuremath{\tau}/${\mathrm{\ensuremath{\tau}}}_{\mathit{c}\mathit{p}\mathit{h}\mathit{i}}$${)}^{\mathit{d}}$] agrees with the results of numerical simulation, although it does not agree with the existing results of physical experiment. We believe that such a disagreement is of a fundamental nature and manifests a basic need for further experimental and theoretical work.

The echo phenomenon is observed in the course of band-to-band transitions produced by two successive pulses of coherent light separated by a time interval tau . It is due to the existence of independent 'two-level systems' represented by mixed electron-hole states with given quasimomenta p. Here we investigate a mechanism responsible for the observed very short times of the echo decay (of the order of a few femtoseconds). It is associated with the loss of phase memory as a result of interaction of the mixed state with the unscreened random Coulomb potential of the photocarriers or with the random static potential of the impurities. We have calculated the phase breaking time tau psi within the framework of the elkonal approximation using a diagrammatic technique. It is shown that tau psi is typically much shorter than both the period of plasma oscillations and the time of electron-electron collisions. It is proportional to n-1d/ (where n is the carrier concentration and d the dimensionality of a system) which is consistent with the experimental results. However, the law of echo decay of the form exp(-( tau / tau psi )3) does not agree with the existing experimental data.

We consider Joule heat release in a quantum wire joining two classical reservoirs under the action of a nonstationary periodic electric field. The rate of heat generation and its spatial distribution is discussed. The heat is spread over the lengths of electron mean free paths in the reservoirs. We find that the total rates of heat generation in both reservoirs that are joined by the nanostructure are the same.

We have investigated within the theory of Fermi liquid dependence of Coulomb drag current in a passive quantum wire on the applied voltage $V$ across an active wire and on the temperature $T$ for any values of $eV/k_BT$. We assume that the bottoms of the 1D minibands in both wires almost coincide with the Fermi level. We come to conclusions that 1) within a certain temperature interval the drag current can be a descending function of the temperature $T$; 2) the experimentally observed temperature dependence $T^{-0.77}$ of the drag current can be interpreted within the framework of Fermi liquid theory; 3) at relatively high applied voltages the drag current as a function of the applied voltage saturates; 4) the screening of the electron potential by metallic gate electrodes can be of importance., Comment: 7 pages, 1 figure

In the quasi‐classical approximation, the theory of fluctuations in a degenerate two‐or three‐dimensional non‐equilibrium electron gas is developed from first principles. It is shown that, thanks to the small‐angle character of the inter‐electron scattering, the theory takes a rather simple and transparent form, in contrast to other types of Fermi gases for which, due to exchange effects, the situation proves to be much more complicated.

Spin-magnetophonon level splitting in a quantum well made of a semimagnetic wide gap semiconductor is considered. The semimagnetic semiconductors are characterized by a large effective $g$ factor. The resonance conditions $\hbar\omega_{\rm LO}=\mu_BgB$ for the spin flip between two Zeeman levels due to interaction with longitudinal optical phonons can be achieved sweeping magnetic field $B$. This condition is studied in quantum wells. It is shown that it leads to a level splitting that is dependent on the electron-phonon coupling strength as well as on the spin-orbit interaction in this structure. We treat in detail the Rashba model for the spin-orbit interaction assuming that the quantum well lacks inversion symmetry and briefly discuss other models. The resonant transmission and reflection of light by the well is suggested as a suitable experimental probe of the level splitting.

A theory of femtosecond photon echo pulse decay in semiconductors is developed. The echo is due to band-to-band transitions produced by two successive pulses of coherent light. We propose that the decay is a result of the unscreened carrier-carrier interaction that brings about dephasing of the electron-hole wave function. We come to the conclusion that the time of dephasing is proportional to n-1/3, where n is the carrier concentration.

The acoustic phonon-mediated contribution to the drag current in the ballistic transport regime in two nearby one-dimensional nanowires is calculated. In the nonlinear regime, where the applied bias voltage eV is greater than the temperature T, the threshold of the phonon-mediated drag current with respect to bias or gate voltage is predicted. It is found that the drag current contribution from any two aligned subbands in the drive and drag wires saturates at large bias (driving) voltage.

As is well known, the fluctuations from a stable stationary nonequilibrium state are described by a linearized nonhomogeneous Boltzmann-Langevin equation. The stationary state itself may be described by a nonlinear Boltzmann equation. The ways of its linearization sometimes seem to be not unique. We argue that there is actually a unique way to obtain a linear equation for the fluctuations. In the present paper we treat as an example an analytical theory of nonequilibrium shot noise in a diffusive conductor under the space charge limited regime. Our approach is compared with that of Schomerus, Mishchenko and Beenakker [Phys. Rev. B 60, 5839 (1999)]. We find some difference between the present theory and the approach of their paper and discuss a possible origin of the difference. We believe that it is related to the fundamentals of the theory of fluctuation phenomena in a nonequilibrium electron gas., Comment: 17 pages, no figures

We work out a theory of the Coulomb drag current created under the ballistic transport regime in a one-dimensional nanowire by a ballistic non-Ohmic current in a nearby parallel nanowire. As in the Ohmic case, we predict sharp oscillation of the drag current as a function of gate voltage or the chemical potential of electrons. We study also dependence of the drag current on the voltage V across the driving wire. For relatively large values of V the drag current is proportional to V^2., Comment: 7 pages, 2 eps figures

The authors investigate a mechanism responsible for the observed very short times of the photon echo decay (of the order of a few femtoseconds) in semiconductors. It is associated with the loss of phase memory as a result of interaction of the mixed state (associated with interband transitions) with an unscreened random Coulomb potential of the photocarriers or with a random static potential of the impurities. Qualitative physical consideration enabling one to visualize the process of echo decay are presented. They have introduced a new time characteristic of a system of interacting electrons. This is the time of phase breaking, {tau}{sub {var_phi}} which they calculate within the eikonal approximation using a diagrammatic technique. It is shown that {tau}{sub {var_phi}} is typically much shorter than both the period of plasma oscillations and the time of electron-electron collisions. The screening of Coulomb potential cannot build up during this time. {tau}{sub {var_phi}} is proportional to n{sup {minus}1/d} (where n is the carrier concentration, d the dimensionality of a system) which is consistent with the experimental results.

The theory of electric-dipole two-pulse echo in semiconductors under the conditions of micronvave hopping conductivity is developed. It is shown that the echo signal is due to the interaction of an a.c. electric field with pairs of neighboring donors. The characteristic spatial distance between them is much smaller than the average distance. Each such pair consists of one impurity center which is occupied by an electron and another center that is empty. Such a pair (the so-called close pair) is a two-level electron system and different pairs have, in general, different interlevel spacings. The interlevel spacings have random values distributed within a wide range of energies of the order of the impurity bandwidth. The echo pulse form is analyzed as a function of the pumping pulse amplitude for a broad range of amplitudes