Quantum-critical spin dynamics in quasi-one-dimensional antiferromagnets

By means of nuclear spin-lattice relaxation rate 1/T1, we follow the spin dynamics as a function of the applied magnetic field in two gapped one-dimensional quantum antiferromagnets: the anisotropic spin-chain system NiCl2-4SC(NH2)2 and the spin-ladder system (C5H12N)2CuBr4. In both systems, spin excitations are confirmed to evolve from magnons in the gapped state to spinons in the gapples Tomonaga-Luttinger-liquid state. In between, 1/T1 exhibits a pronounced, continuous variation, which is shown to scale in accordance with quantum criticality. We extract the critical exponent for 1/T1, compare it to the theory, and show that this behavior is identical in both studied systems, thus demonstrating the universality of quantum critical behavior

Microwave response of thin niobium films under perpendicular static magnetic fields

The microwave response of high quality niobium films in a perpendicular static magnetic field has been investigated. The complex frequency shift was measured up to the upper critical fields. The data have been analyzed by the effective conductivity model for the type-II superconductors in the mixed state. This model is found to yield consistent results for the coherence lengths in high-kappa superconducting samples, and can be used with HTSC even at temperatures much below T_c. It is shown that for samples with high values of depinning frequency, one should measure both components of the complex frequency shift in order to determine the flow resistivity. The thick Nb film (160 nm) has low resistivity at 10 K, comparable to the best single crystals, and low kappa value. In contrast, the thinnest (10 nm) film has kappa ~ 9.5 and exhibits a high depinning frequency (~20 GHz). The upper critical field determined from microwave measurements is related to the radius of nonoverlaping vortices, and appears to be larger than the one determined by the transition to the normal state.Comment: 8 pages, 7 figures; submitted to PRB; measured rho_n; changes due to the referees' comments (abstract, conclusions, extended introduction

Household food waste in Belgrade - sin and unconcern

The aim of this study was to examine the actual procedures with food in households and consumer attitudes about food waste. The survey was conducted in 83 households in Belgrade, Serbia. All participants were interviewed using a standardized questionnaire. The results obtained show that awareness of food waste is at a satisfactory level, but the actual situation is that food is discarded in large quantities, even though people are aware of what a global problem this is. Large contradictions were observed among the respondents answers in this study. Respondents who stated that they never discard food, in further responses, declared they throw away significant amounts of food for various reasons (too long storage, overconsumption, improper preparation, etc.). We conclude that people are either unaware of how much food they discard, or they do not want to admit it to themselves. However, participants largely have a sense of guilt about discarding food. This indicates consumer awareness of food waste, and is an encouraging sign that further education could be effective in consumers taking into account their food waste habits, starting from procurement planning, through storage and preparation

In Vitro Callus Induction from Adult Tissues of Japanese Flowering Cherry Trees and Two Cherry Rootstocks

Several in vitro biotechnological techniques have been developed, all of which require a reliable protocol to produce a responsive callus mass. One of these techniques is callus fusion in vitro, which is reliable for the early detection of (in)compatibility of scions and rootstocks. In this paper, the possibility to obtain friable callus tissues was explored by callus induction of adult tissues of Japanese flowering cherry trees from the group Sato zakura (Prunus serrulata 'Amanogawa', 'Kanzan' and 'Kiku-shidare-zakura') and two domestic cherry rootstocks -Prunus avium and Prunus 'Colt'. The explants used in the research were: leaf petiole, leaf base with a part of a petiole, part of lamina with a midvein and a stem with an axillary bud. Among three plant growth media (MS, SH and WP) that were used in this study, the MS proved to be the most favourable for the majority of taxa during the callus induction process. For the sweet cherry tree and the cultivars 'Kanzan' and 'Colt', the SH plant growth medium was also acceptable. The best results in callogenesis were obtained for the majority of taxons with auxin at the concentration 2 mgL-1 NAA and cytokinin BAP 0.5 mgL-1. It is also possible to use 2.4-D at the same concentration as a substitute for the genotypes Prunus avium, Prunus ` Colt' and Prunus serrulata 'Kanzan', whereas IBA proved to be an inappropriate auxin for callus induction. The protocol described herein is proved to be efficient callus induction in a range of taxa of genus Prunus

Effect of camphor essential oil on rat cerebral cortex activity as manifested by fractal dimension changes

The aim of our study was to investigate the effect of camphor essential oil on rat cerebral cortex activity by fractal analysis. Fractal dimension (FD) values of the parietal electrocortical activity were calculated before and after intra-peritoneal administration of camphor essential oil (450-675 μl/kg) in anesthetized rats. Camphor oil induced seizure-like activity with single and multiple spiking of high amplitudes in the parietal electrocorticogram and occasional clonic limb convulsions. The FD values of cortical activity after camphor oil administration increased on the average. Only FD values of cortical ECoG sequences were lower than those before camphor oil administration.Cilj naše studije je bilo istraživanje efekta kamforovog esencijalnog ulja na aktivnost kore velikog mozga pacova pomoću fraktalne analize. Vrednosti fraktalne dimenzije parijetalne elektrokortikalne aktivnosti su izračunate pre i posle davanja kamforovog esencijalnog ulja (450-675 μl/kg,i.p.) anesteziranim pacovima. Kamforovo esencijalno ulje izazvalo je moždanu aktivnost nalik na napad sa pojedinačnim i višestrukim šiljak-talasima velike amplitude u parijetalnom elektrokortikogramu kao i povremene klonične konvulzije ekstremiteta. Posle davanja kamforovog ulja, srednje vrednosti fraktalne dimenzije kortikalne aktivnosti suse povećale u proseku. Jedino vrednosti fraktalne dimenzije iktalnih sekvenci elektrokortikograma su bile niže nego one pre davanja kamforovog ulja.Projekat ministarstva br. 14302

Upper critical field, penetration depth, and depinning frequency of the novel high-temperature superconductor LaFeAsO0.9_{0.9}F0.1_{0.1} studied by microwave surface impedance

Temperature and magnetic field dependent measurements of the microwave surface impedance of superconducting LaFeAsO$_{0.9}$F$_{0.1}$ (\Tc $\approx$ 26K) reveal a very large upper critical field ($B_{\rm c2} \approx 56$T) and a large value of the depinning frequency ($f_{0}\approx 6$GHz); together with an upper limit for the effective London penetration depth, $\lambda_{\rm eff} \le 200 \rm nm$, our results indicate a strong similarity between this system and the high-$T_{\rm c}$ superconducting cuprates.Comment: 4 pages, 6 figures, minor corrections and rephrasin

Singlet state formation and its impact on magnetic structure in tetramer system SeCuO3_3

We present an experimental investigation of the magnetic structure in a tetramer system SeCuO$_3$ using neutron diffraction and nuclear resonance techniques. We establish a non-collinear, commensurate antiferromagnetic ordering with a propagation vector $\textbf{k} = \left(0,0,1 \right)$. The order parameter follows a critical behavior near $T_N = 8$ K, with a critical exponent $\beta = 0.32$ in agreement with a 3D universality class. Evidence is presented that a singlet state starts to form on tetramers at temperatures as high as 200 K, and its signature is preserved within the ordered state through a strong renormalization of the ordered magnetic moment on two non-equivalent copper sites, $m_{Cu1} \approx 0.4 \mu_B$ and $m_{Cu2} \approx 0.7 \mu_B$ at 1.5 K

Abscisic Acid Insensitive 4 transcription factor is an important player in the response of Arabidopsis thaliana to two-spotted spider mite (Tetranychus urticae) feeding.

Plants growing in constantly changeable environmental conditions are compelled to evolve regulatory mechanisms to cope with biotic and abiotic stresses. Effective defence to invaders is largely connected with phytohormone regulation, resulting in the production of numerous defensive proteins and specialized metabolites. In our work, we elucidated the role of the Abscisic Acid Insensitive 4 (ABI4) transcription factor in the plant response to the two-spotted spider mite (TSSM). This polyphagous mite is one of the most destructive herbivores, which sucks mesophyll cells of numerous crop and wild plants. Compared to the wild-type (Col-0) Arabidopsis thaliana plants, the abi4 mutant demonstrated increased susceptibility to TSSM, reflected as enhanced female fecundity and greater frequency of mite leaf damage after trypan blue staining. Because ABI4 is regarded as an important player in the plastid-to-nucleus retrograde signalling process, we investigated the plastid envelope membrane dynamics using stroma-associated fluorescent marker. Our results indicated a clear increase in the number of stroma-filled tubular structures deriving from the plastid membrane (stromules) in the close proximity of the site of mite leaf damage, highlighting the importance of chloroplast-derived signals in the response to TSSM feeding activity

Cross-talk between high light stress and plant defence to the two-spotted spider mite in Arabidopsis thaliana

Little is known about how plants deal with arthropod herbivores under the fluctuating light intensity and spectra which occur in natural environments. Moreover, the role of simultaneous stress such as excess light (EL) in the regulation of plant responses to herbivores is poorly characterized. In the current study, we focused on a mite-herbivore, specifically, the two-spotted spider mite (TSSM), which is one of the major agricultural pests worldwide. Our results showed that TSSM-induced leaf damage (visualized by trypan blue staining) and oviposition rate (measured as daily female fecundity) decreased after EL pre-treatment in wild-type Arabidopsis plants, but the observed responses were not wavelength specific. Thus, we established that EL pre-treatment reduced Arabidopsis susceptibility to TSSM infestation. Due to the fact that a portion of EL energy is dissipated by plants as heat in the mechanism known as non-photochemical quenching (NPQ) of chlorophyll fluorescence, we tested an Arabidopsis npq4-1 mutant impaired in NPQ. We showed that npq4-1 plants are significantly less susceptible to TSSM feeding activity, and this result was not dependent on light pre-treatment. Therefore, our findings strongly support the role of light in plant defence against TSSM, pointing to a key role for a photo-protective mechanism such as NPQ in this regulation. We hypothesize that plants impaired in NPQ are constantly primed to mite attack, as this seems to be a universal evolutionarily conserved mechanism for herbivores