Field Induced Staggered Magnetization and Magnetic Ordering in Cu2(C5H12N2)2Cl4Cu_2 (C_5 H_{12} N_2)_2 Cl_4

We present a $^2$D NMR investigation of the gapped spin-1/2 compound $Cu_2 (C_5 H_{12} N_2)_2 Cl_4$. Our measurements reveal the presence of a magnetic field induced transverse staggered magnetization (TSM) which persists well below and above the field-induced 3D long-range magnetically ordered (FIMO) phase. The symmetry of this TSM is different from that of the TSM induced by the order parameter of the FIMO phase. Its origin, field dependence and symmetry can be explained by an intra-dimer Dzyaloshinskii-Moriya interaction, as shown by DMRG calculations on a spin-1/2 ladder. This leads us to predict that the transition into the FIMO phase is not in the BEC universality class.Comment: 4 page

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

Anisotropy of Magnetic Interactions in the Spin-Ladder Compound (C5_5H12_{12}N)2_2CuBr4_4

Magnetic excitations in the spin-ladder material (C$_5$H$_{12}$N)$_2$CuBr$_4$ [BPCB] are probed by high-resolution multi-frequency electron spin resonance (ESR) spectroscopy. Our experiments provide a direct evidence for a biaxial anisotropy ($\sim 5\%$ of the dominant exchange interaction), that is in contrast to a fully isotropic spin-ladder model employed for this system previously. It is argued that this anisotropy in BPCB is caused by spin-orbit coupling, which appears to be important for describing magnetic properties of this compound. The zero-field zone-center gap in the excitation spectrum of BPCB, $\Delta_0/k_{B}=16.5$ K, is detected directly. Furthermore, an ESR signature of the inter-ladder exchange interactions is obtained. The detailed characterization of the anisotropy in BPCB completes the determination of the full spin hamiltonian of this exceptional spin-ladder material and shows ways to study anisotropy effects in spin ladders.Comment: 6 pages, 6 figure

Peptidomic approach for the identification of peptides with potential antioxidant and anti-hyperthensive effects derived from Asparagus by-products

Asparagus waste represents products of great interest since many compounds with high biological value are located in the lower portion of the spears. The extraction of bioactive compounds from asparagus by-products is therefore crucial for the purpose of adding value to these by-products. In this paper, bioactive peptides from asparagus waste were extracted, digested, purified and identified. In particular, Alcalase® was chosen as the enzyme to use to obtain protein hydrolysate due to its low cost and, consequently, the possibility of implementing the method on a large scale. In order to simplify the peptide extract to reach better identification, the hydrolysate was fractionated by reversed-phase chromatography in 10 fractions. Two tests were carried out for antioxidant activity (ABTS-DPPH) and one for antihypertensive activity (ACE). Fractions with a higher bioactivity score were identified by peptidomics technologies and screened for bioactivity with the use of bioinformatics. For ACE-inhibitor activity, two peptides were synthetized, PDWFLLL and ASQSIWLPGWL, which provided an EC50 value of 1.76 µmol L-1 and 4.02 µmol L-1, respectively. For the antioxidant activity, by DPPH assay, MLLFPM exhibited the lowest EC50 value at 4.14 µmol L-1, followed by FIARNFLLGW and FAPVPFDF with EC50 values of 6.76 µmol L-1 and 10.01 µmol L-1, respectively. A validation of the five identified peptides was also carried out. The obtained results showed that peptides obtained from asparagus by-products are of interest for their biological activity and are suitable for being used as functional ingredients

Identification of Nuclear Relaxation Processes in a Gapped Quantum Magnet: Proton NMR in the S=1/2 Heisenberg Ladder Cu2(C5H12N2)2Cl4

The proton hyperfine shift K and NMR relaxation rate $1/T_1$ have been measured as a function of temperature in the S=1/2 Heisenberg antiferromagnetic ladder Cu2(C5H12N2)2Cl4. The presence of a spin gap $\Delta \simeq J_\perp-J_\parallel$ in this strongly coupled ladder ($J_\parallel < J_\perp$) is supported by the K and $1/T_1$ results. By comparing $1/T_1$ at two different proton sites, we infer the evolution of the spectral functions $S_z(q,\omega_n)$ and $S_\perp(q,\omega_n)$. When the gap is significantly reduced by the magnetic field, two different channels of nuclear relaxation, specific to gapped antiferromagnets, are identified and are in agreement with theoretical predictions.Comment: 4 pages, 4 figures, to be published in Phys. Rev. Letter

Evaluation of the static equilibrium in a sample of hearing impaired children

A random sample was organized with 42 children with congenital sensorineural auditory deficit (severe and bilateral) from special education schools in Campinas. Chronological ages ranged from 4 to 7 years of age. This sample was compared with two control groups of 42 children of the same chronological age but attending normal classes. All were submitted to 9 tests of the set of static equilibrium of the Evolutive Neurologic Examination. It was observed that in the position of equilibrium with opened eyes (test 8) there were no differences between the groups. In the Romberg position, the hearing impaired children of 4, 5 and 6 years of age showed a significant decrease in the ability to do the test (test 9); those of 7 years of age had equal ability whether of the control or the deficient groups. Hearing impaired children were less able to do other static equilibrium tests (heel-toe or one foot or tip-toe standing tests, with opened or closed eyes: tests 10, 12, 16, 20, 24, 25 and 26). The use of detailed neurological semiology allowed us to support the alteration of the static equilibrium in this group of hearing impaired children.Foi constituída amostra aleatória de 42 crianças deficientes auditivas neurossen-soriais congênitas, profundas e bilaterais, com idade cronológica variando entre 4 e 7 anos, que frequentavam classes de habilitação da cidade de Campinas. As crianças propostas foram comparadas) às de dois grupos controles de 42 crianças, da mesma faixa etária, que apresentavam bom rendimento escolar em classe comum. Todas foram submetidas a 9 provas do setor de equilíbrio estático do Exame Neurológico Evolutivo. Verificou-se que, na posição de equilíbrio com olhos abertos, não houve diferença entre os grupos. Na posição de Romberg, foi significativamente menor o número de deficientes auditivos que a realizaram aos 4, 5 e 6 anos; aos 7 anos foi executada por igual número de controles e deficientes auditivos. As demais provas foram realizadas por número significativamente menor de deficientes auditivos nas seguintes posturas: artelho-calcâneo com olhos abertos ou fechados (provas 24 e 25), permanecer num pé só (provas 12 e 16) ou nas pontas dos pés (provas 10 e 16). O uso de semiologia neurológica detalhada permitiu documentar as alterações do equilíbrio estático nesse grupo de crianças deficientes auditivas.34635

The LRRK2 G2385R variant is a partial loss-of-function mutation that affects synaptic vesicle trafficking through altered protein interactions.

Mutations in the Leucine-rich repeat kinase 2 gene (LRRK2) are associated with familial Parkinson's disease (PD). LRRK2 protein contains several functional domains, including protein-protein interaction domains at its N- and C-termini. In this study, we analyzed the functional features attributed to LRRK2 by its N- and C-terminal domains. We combined TIRF microscopy and synaptopHluorin assay to visualize synaptic vesicle trafficking. We found that N- and C-terminal domains have opposite impact on synaptic vesicle dynamics. Biochemical analysis demonstrated that different proteins are bound at the two extremities, namely \u3b23-Cav2.1 at N-terminus part and \u3b2-Actin and Synapsin I at C-terminus domain. A sequence variant (G2385R) harboured within the C-terminal WD40 domain increases the risk for PD. Complementary biochemical and imaging approaches revealed that the G2385R variant alters strength and quality of LRRK2 interactions and increases fusion of synaptic vesicles. Our data suggest that the G2385R variant behaves like a loss-of-function mutation that mimics activity-driven events. Impaired scaffolding capabilities of mutant LRRK2 resulting in perturbed vesicular trafficking may arise as a common pathophysiological denominator through which different LRRK2 pathological mutations cause diseas

Neurologic semiology in a sample of hearing impaired children

A random sample of 42 sensorioneural hearing impaired children (severe and bilateral) was studied, from special classes in Campinas, with chronological ages varying between 4 and 7 years old. The children of this sample were compared with two control groups of 42 children of the same chronological age, from regular classes of private and public schools. All of them were submitted to the traditional neurological examination. Hearing impaired children showed differences as to head circumference and muscle tonus. In the other examined items we found motor hyperactivity, cerebellar and ocular syndromes although there were no significant differences between the groups.Foi constituída uma amostra aleatória de 42 crianças deficientes auditivas neuros-sensoriaís congênitas, profundas e bilaterais, com idade cronológica variando entre 4 e 7 anos, que frequentavam classes de habilitação da cidade de Campinas. As crianças propostas foram comparadas com dois grupos controles de 42 crianças, da mesma faixa etária, de classe comum. Todas foram submetidas ao exame neurológico tradicional. Verificou-se que os aspectos que demonstraram diferenças foram o perímetro craniano e o tono muscular. Nos demais itens avaliados, mostrou-se hiperatividade motora, síndrome cerebelar e síndrome ocular, porém não houve diferença significativa entre os dois grupos.34134

NMR study of the S=1/2 Heisenberg Ladder Cu2(C5H12N2)2Cl4 : Quantum phase transition and critical dynamics

We present an extensive NMR study of the spin-1/2 antiferromagnetic Heisenberg ladder Cu2(C5H12N2)2Cl4 in a magnetic field range 4.5 - 16.7 T. By measuring the proton NMR relaxation rate 1/T_1 and varying the magnetic field around the critical field H_c1 = Delta / g\mu_B = 7.5 T, we have studied the transition from a gapped spin liquid ground state to a gapless magnetic regime which can be described as a Luttinger liquid. We identify an intermediate regime T > |H-H_c1|, where the spin dynamics is (possibly) only controlled by the T=0 critical point H_c1.Comment: 4 pages, 3 eps figures, submitted to Phys. Rev. Let