Magnetic properties of Sn/1-x/Cr/x/Te diluted magnetic semiconductors

We present the studies of Sn/1-x/Cr/x/Te semimagnetic semiconductors with chemical composition x ranging from 0.004 to 0.012. The structural characterization indicates that even at low average Cr-content x < ?0.012, the aggregation into micrometer size clusters appears in our samples. The magnetic properties are affected by the presence of clusters. In all our samples we observe the transition into the ordered state at temperatures between 130 and 140 K. The analysis of both static and dynamic magnetic susceptibility data indicates that the spin-glass-like state is observed in our samples. The addition of Cr to the alloy seems to shift the spin-glass-like transition from 130 K for x = 0.004 to 140 K for x = 0.012.Comment: 4 pages, 4 figure

The magnetic interactions in spin-glasslike Ge/1-x-y/Sn/x/Mn/y/Te diluted magnetic semiconductor

We investigated the nature of the magnetic phase transition in the Ge/1-x-y/Sn/x/Mn/y/Te mixed crystals with chemical composition changing in the range of 0.083 < x < 0.142 and 0.012 < y < 0.119. The DC magnetization measurements performed in the magnetic field up to 90 kOe and temperature range 2-200 K showed that the magnetic ordering at temperatures below T = 50 K exhibits features characteristic for both spin-glass and ferromagnetic phases. The modified Sherrington - Southern model was applied to explain the observed transition temperatures. The calculations showed that the spin-glass state is preferred in the range of the experimental carrier concentrations and Mn content. The value of the Mn hole exchange integral was estimated to be J/pd/ = 0.45+/-0.05 eV. The experimental magnetization vs temperature curves were reproduced satisfactory using the non-interacting spin-wave theory with the exchange constant J/pd/ values consistent with those calculated using modified Sherrington - Southern model. The magnetization vs magnetic field curves showed nonsaturating behavior at magnetic fields B < 90 kOe indicating the presence of strong magnetic frustration in the system. The experimental results were reproduced theoretically with good accuracy using the molecular field approximation-based model of a disordered ferromagnet with long-range RKKY interaction.Comment: 9 pages, 6 figure

Morphology of PbTe crystal surface sputtered by argon plasma under Secondary Neutral Mass Spectrometry conditions

We have investigated morphology of the lateral surfaces of PbTe crystal samples grown from melt by the Bridgman method sputtered by Ar+ plasma with ion energy of 50-550 eV for 5-50 minutes under Secondary Neutral Mass Spectrometry (SNMS) conditions. The sputtered PbTe crystal surface was found to be simultaneously both the source of sputtered material and the efficient substrate for re-deposition of the sputtered material during the depth profiling. During sputtering PbTe crystal surface is forming the dimple relief. To be redeposited the sputtered Pb and Te form arrays of the microscopic surface structures in the shapes of hillocks, pyramids, cones and others on the PbTe crystal sputtered surface. Correlation between the density of re-deposited microscopic surface structures, their shape, and average size, on the one hand, and the energy and duration of sputtering, on the other, is revealed

Хірургічне лікування хордоми крижів

Мета. Аналіз хірургічної техніки, результатів хірургічного та комбінованого лікування хордоми крижів. Матеріали і методи. У 28 хворих з хордомами крижів проаналізовано симптоми захворювання та їх динаміку, цін- ність методів нейровізуалізації, особливості патогістологічної картини, хірургічну техніку, ефективність променевої те- рапії та віддалені результати лікування. Результати. Серед клінічних проявів хордоми крижів домінував больовий синдром. Середня тривалість анамнезу ста- новила близько одного року. Хірургічну резекцію пухлини через задній доступ виконали 18 хворим, через комбінова- ний – 9 хворим. Видалення пухлин оцінене як радикальне у 21 хворого, часткове – у 7 хворих. У післяопераційному періоді всім хворим проведено курс променевої терапії на лінійному прискорювачі. Протягом 5 років у 26 хворих ви- ник рецидив хордоми. Повторне оперативне втручання виконали 22 хворим. Висновки. Лікування хордом потребує комплексного підходу. Методом вибору залишається виконання радикального хірургічного втручання, що можливо не у всіх хворих

Calibration of optimal execution of financial transactions in the presence of transient market impact

Trading large volumes of a financial asset in order driven markets requires the use of algorithmic execution dividing the volume in many transactions in order to minimize costs due to market impact. A proper design of an optimal execution strategy strongly depends on a careful modeling of market impact, i.e. how the price reacts to trades. In this paper we consider a recently introduced market impact model (Bouchaud et al., 2004), which has the property of describing both the volume and the temporal dependence of price change due to trading. We show how this model can be used to describe price impact also in aggregated trade time or in real time. We then solve analytically and calibrate with real data the optimal execution problem both for risk neutral and for risk averse investors and we derive an efficient frontier of optimal execution. When we include spread costs the problem must be solved numerically and we show that the introduction of such costs regularizes the solution.Comment: 31 pages, 8 figure

GC-based chemoprofile of lipophilic compounds in Altaian Ganoderma lucidum sample

The presented data contains information about component composition of lipophilic compounds in Ganoderma lucidum fungal body sample obtained using gas chromatography and subsequent mass spectrometry