Spin paramagnetism in d-wave superconductors

The Ginzburg-Landau equations are derived from the microscopic theory for clean layered superconductors with $d_{x^2-y^2}$ pairing symmetry, including the Pauli paramagnetism effect. The upper critical field $H_{c2}$ parallel to the $c$ axis is calculated. A comparison with the experimental data for YBCO suggests that, relative to the orbital effect, the Pauli paramagnetism contribution to $H_{c2}$ is significant. The reversible magnetization $M$ in high magnetic fields is also calculated, showing strong temperature dependence of the slope $dM/dH$, as a consequence of the spin paramagnetism. A simple expression for the high temperature spin susceptibility is derived, in a good agreement with the Knight shift measurements on YBCO.Comment: 8 pages, 3 figures; minor changes are included; reference 35 is added; shorter version will be published in Phys. Rev. B, scheduled issue 01 July 200

Quasiparticle energy spectrum in ferromagnetic Josephson weak links

The quasiparticles energy spectrum in clean ferromagnetic weak links between conventional superconductors is calculated. Large peaks in DOS, due to a special case of Andreev reflection at the ferromagnetic barrier, correspond to spin-splitt bound states. Their energies are obtained as a function of the barrier thickness, exchange field strength, and of the macroscopic phase difference $\phi$ at the link, related to the Josephson current. In the ground state, $\phi$ can be 0 or $\pi$, depending on the ferromagnetic barrier influence. Conditions for the appearence of the zero-energy bound states (ZES) and for the spin polarized ground state (SPGS) are obtained analytically. It is shown that ZES appear only outside the weak link ground state.Comment: 11 pages, 6 figure

Dynamic polarization of graphene by moving external charges: random phase approximation

We evaluate the stopping and image forces on a charged particle moving parallel to a doped sheet of graphene by using the dielectric response formalism for graphene's $\pi$-electron bands in the random phase approximation (RPA). The forces are presented as functions of the particle speed and the particle distance for a broad range of charge-carrier densities in graphene. A detailed comparison with the results from a kinetic equation model reveal the importance of inter-band single-particle excitations in the RPA model for high particle speeds. We also consider the effects of a finite gap between graphene and a supporting substrate, as well as the effects of a finite damping rate that is included through the use of Mermin's procedure. The damping rate is estimated from a tentative comparison of the Mermin loss function with a HREELS experiment. In the limit of low particle speeds, several analytical results are obtained for the friction coefficient that show an intricate relationship between the charge-carrier density, the damping rate, and the particle distance, which may be relevant to surface processes and electrochemistry involving graphene.Comment: 14 pages, 10 figures, accepted for publication in Phys. Rev.

Meron ground states of quantum Hall droplets

We argue that topological meron excitations, which are in a strong coupling phase (bound in pairs) in infinite quantum Hall ferromagnets, become deconfined in finite size quantum Hall systems. Although effectively for larger systems meron energy grows with the size of the system, when gyromagnetic ratio is small meron becomes the lowest lying state of a quantum Hall droplet. This comes as a consequence of the many-body correlations built in the meron construction that minimize the interaction energy. We demonstrate this by using mean field ansatzes for meron wave function. The ansatzes will enable us to consider much larger system sizes than in the previous work [A. Petkovic and M.V. Milovanovic, PRL 98, 066808 (2007)], where fractionalization into merons was introduced.Comment: 6 pages, 6 figure

KONTROLA STRANIH DIREKTNIH INVESTICIJA U PRAVU EU U USLOVIMA KRIZE IZAZVANE PANDEMIJOM

The European Union is generally open to inward foreign direct investments (FDI). However, over recent years there is a rising trend in screening of inward FDI from third countries in the Member States. As a result, the Regulation (EU) 2019/452 on screening of foreign direct investments was enacted. In this paper the author, firstly, explains the reasons for a change in treatment of inward FDI from third countries within the Member States and the EU itself. The second part of the paper contains an analysis of the legal framework for FDI in the EU, in order to determine the possibility of their restrictions through national legislations. Special attention is given to the FDI-Screening Regulation and its minimum standards for national screening mechanisms. Finally, the author examines how the COVID-19 pandemic affects the treatment of FDI in the EU and concludes that the current crisis has contributed to further expanding the scope and importance of their screening and control.Poslednjih godina primetan je trend u pravcu češće i šire kontrole stranih direktnih investicija (SDI) iz trećih zemalja u okviru nacionalnih prava država članica EU. Stoga je to pitanje uređeno na komunitarnom nivou Uredbom (EU) 2019/452 o proveri SDI. U radu su objašnjeni razlozi promene odnosa prema unutrašnjim SDI iz trećih zemalja u državama članicama, a onda i na nivou EU. Potom je analiziran pravni okvir za SDI u EU, kako bi se utvrdile mogućnosti njihovog ograničavanja nacionalnim pravima. Posebna pažnja je posvećena Uredbi (EU) 2019/452, koja postavlja minimalne standarde za nacionalne mehanizme provere SDI. Konačno, autorka ispituje uticaj pandemije na odnos prema SDI u EU i zaključuje da je aktuelna kriza doprinela učvršćenju i daljem razvoju njihove kontrole

Genetic Variability in Different Lucerne (\u3cem\u3eMedicago Sativa\u3c/em\u3e) Genotypes

One of the basic goals of modern lucerne breeding programmes is creation of new cultivars with a great potential for high quality and stable yields of both forage and hay (Riday & Brummer, 2002). Such cultivars meet increased needs of animal husbandry and must contribute to diverse farming systems (Luki , 2000). Our trial was aimed at determining genetic variability of yield components in 7 lucerne genotypes, as well as at evaluation of their breeding potential as gene donors to new lucerne cultivar

Subwavelength hole arrays with nanoapertures fabricated by scanning probe nanolithography

Owing to their surface plasmon-based operation, arrays of subwavelength holes show extraordinary electromagnetic transmission and intense field localizations of several orders of magnitude. Thus they were proposed as the basic building blocks for a number of applications utilizing the enhancement of nonlinear optical effects. We designed and simulated nanometer-sized subwavelength holes using an analytical approach. In our experiments we used the scanning probe method for nanolithographic fabrication of subwavelength hole arrays in silver layers sputtered on a positive photoresist substrate. We fabricated ordered nanohole patterns with different shapes, dispositions and proportions. The smallest width was about 60 nm. We characterized the fabricated samples by atomic force microscopy

Bistability in superconducting rings containing an inhomogeneous Josephson junction

We investigate the magnetic response of a superconducting Nb ring containing a ferromagnetic PdNi Josephson junction and a tunnel junction in parallel. A doubling of the switching frequency is observed within certain intervals of the external magnetic field. Assuming sinusoidal current-phase relations of both junctions our model of a dc-SQUID embedded within a superconducting ring explains this feature by a sequence of current reversals in the ferromagnetic section of the junction in these field intervals. The switching anomalies are induced by the coupling between the magnetic fluxes in the two superconducting loops.Comment: 5 pages, 4 figure

Distribution of Craniofacial Variables in South Dalmatian and Middle Croatian Populations

The objective of the present work was to determine some relevant craniofacial parameters, particularly in relation to sex, for the study of the distribution of basic head and face types, and to investigate craniofacial and morphological differences between two population samples. The study sample comprised 100 subjects of both sex aged 18 to 30 from South Dalmatia and 200 subjects from Middle Croatia. Eight basic craniofacial variables were measured to obtain head, forehead and face indexes. The data indicate that average values of all variables can be used as standard craniofacial parameters for the examined population groups. All the craniofacial variables are considerably higher in men than in women (p < 0.05). In the South Dalmatian population mesocephalia (48.0%) and leptoprosopia (82.0%) prevail, while in the Middle Croatian population the brachycephalia (62.0%), and euriprosopia (73.5%) are present to a greater degree. The most significant craniofacial and morphological differences between the examined study samples are head width (Eu–Eu), face width (Zy–Zy), and forehead height (Tr–N). They were found to be statistically significant in the examined Middle Croatian population (p < 0.05). The presented measurements are highly relevant to orthodontic diagnostics and therapy

The influence of heat input on the toughness and fracture mechanism of surface weld metal

© 2018 The Authors. Surface welding is a way to extend the exploitation life of damaged parts and constructions and the heat input has a major influence on the weldment properties. In this paper is shown the influence of the heat input on the toughness and the fracture mechanism of the surface welded joint. Surface welding of high carbon steel with self shielded wire was conducted with three different heat inputs (6kJ/cm, 10 kJ/cm and 16 kJ/cm). Total impact energy, crack initiation and crack propagation energy were estimated at room temperature, -20 o C and -40 o C. Fracture analysis of fractured surfaces was also conducted and it has been found that increasing of heat input leads to an increase of share of transgranular brittle fracture, what is in complete accordance with the obtained energy values. Based on all obtained results, the optimum value of heat input for welding procedure applied was defined