Harnessing nuclear spin polarization fluctuations in a semiconductor nanowire

Soon after the first measurements of nuclear magnetic resonance (NMR) in a condensed matter system, Bloch predicted the presence of statistical fluctuations proportional to $1/\sqrt{N}$ in the polarization of an ensemble of $N$ spins. First observed by Sleator et al., so-called "spin noise" has recently emerged as a critical ingredient in nanometer-scale magnetic resonance imaging (nanoMRI). This prominence is a direct result of MRI resolution improving to better than 100 nm^3, a size-scale in which statistical spin fluctuations begin to dominate the polarization dynamics. We demonstrate a technique that creates spin order in nanometer-scale ensembles of nuclear spins by harnessing these fluctuations to produce polarizations both larger and narrower than the natural thermal distribution. We focus on ensembles containing ~10^6 phosphorus and hydrogen spins associated with single InP and GaP nanowires (NWs) and their hydrogen-containing adsorbate layers. We monitor, control, and capture fluctuations in the ensemble's spin polarization in real-time and store them for extended periods. This selective capture of large polarization fluctuations may provide a route for enhancing the weak magnetic signals produced by nanometer-scale volumes of nuclear spins. The scheme may also prove useful for initializing the nuclear hyperfine field of electron spin qubits in the solid-state.Comment: 18 pages, 5 figure

Adiabatic perturbation theory and geometry of periodically-driven systems

We give a systematic review of the adiabatic theorem and the leading non-adiabatic corrections in periodically-driven (Floquet) systems. These corrections have a two-fold origin: (i) conventional ones originating from the gradually changing Floquet Hamiltonian and (ii) corrections originating from changing the micro-motion operator. These corrections conspire to give a Hall-type linear response for non-stroboscopic (time-averaged) observables allowing one to measure the Berry curvature and the Chern number related to the Floquet Hamiltonian, thus extending these concepts to periodically-driven many-body systems. The non-zero Floquet Chern number allows one to realize a Thouless energy pump, where one can adiabatically add energy to the system in discrete units of the driving frequency. We discuss the validity of Floquet Adiabatic Perturbation Theory (FAPT) using five different models covering linear and non-linear few and many-particle systems. We argue that in interacting systems, even in the stable high-frequency regimes, FAPT breaks down at ultra slow ramp rates due to avoided crossings of photon resonances, not captured by the inverse-frequency expansion, leading to a counter-intuitive stronger heating at slower ramp rates. Nevertheless, large windows in the ramp rate are shown to exist for which the physics of interacting driven systems is well captured by FAPT.The authors would like to thank M. Aidelsburger, M. Atala, E. Dalla Torre, N. Goldman, M. Heyl, D. Huse, G. Jotzu, C. Kennedy, M. Lohse, T. Mori, L. Pollet, M. Rudner, A. Russomanno, and C. Schweizer for fruitful discussions. This work was supported by AFOSR FA9550-16-1-0334, NSF DMR-1506340, ARO W911NF1410540, and the Hungarian research grant OTKA Nos. K101244, K105149. M. K. was supported by Laboratory Directed Research and Development (LDRD) funding from Berkeley Lab, provided by the Director, Office of Science, of the U.S. Department of Energy under Contract No. DE-AC02-05CH11231. The authors are pleased to acknowledge that the computational work reported in this paper was performed on the Shared Computing Cluster which is administered by Boston University's Research Computing Services. The authors also acknowledge the Research Computing Services group for providing consulting support which has contributed to the results reported within this paper. The study of the driven non-integrable transverse-field Ising model was carried out using QuSpin [185] - an open-source state-of-the-art Python package for dynamics and exact diagonalization of quantum many body systems, available to download here. (FA9550-16-1-0334 - AFOSR; DMR-1506340 - NSF; W911NF1410540 - ARO; K101244 - Hungarian research grant OTKA; K105149 - Hungarian research grant OTKA; DE-AC02-05CH11231 - Laboratory Directed Research and Development (LDRD) funding from Berkeley Lab)https://arxiv.org/pdf/1606.02229.pd

The il1β have a protective action in the acute phase of the pilocarpine-induced epilepsy model

INTRODUCTION: There is contradictory information regarding the of effects il1β and il1rn in epilepsy. We aimed to evaluate the effect of silencing both genes in the acute phase of the pilocarpine-induced epilepsy model. METHODS: We used RNA interference in order to achieve gene silencing. RESULTS: We obtained significant gene silencing in the central nervous system. In addition, we observed phenotypic effects including differences in mortality rates of animals 5 days after pilocarpine injections. CONCLUSION: Our results indicate that il1β seems to have a protective effect in the acute phase of the pilocarpine-induced epilepsy model.INTRODUÇÃO: Existem contradições na literatura quanto aos efeitos dos genes il1β e il1rn nas epilepsias. Nosso objetivo foi avaliar os efeitos do silenciamento desses dois genes na fase aguda do modelo de epilepsia induzido pela pilocarpina. MÉTODOS: Para alterar a expressão dos genes il1β e il1rn utilizamos a técnica de interferência por RNA. RESULTADOS: Obtivemos taxas de silenciamento significativas para os dois genes no sistema nervoso central. Observamos efeitos fenotípicos significativos, incluindo a alteração na taxa de mortalidade dos animais 5 dias após a indução do modelo. CONCLUSÕES: A il1β parece exercer um papel protetor na fase aguda do modelo de epilepsia induzido pela pilocarpina.979

Anastomose mamária interna-artéria pulmonar para o tratamento paliativo das cardiopatias congênitas cianóticas Internal mammary-pulmonary artery anastomosis for cyanotic congenital heart disease

As anastomoses sistêmico-pulmonares continuam sendo um importante procedimento no tratamento e na preparação dos cardiópatas cianóticos, com hipoplasia das artérias pulmonares, para a correção total. Todas têm vantagens e desvantagens e os resultados dependerão de idade e peso dos pacientes e da complexidade da cardiopatia. O presente estudo relata a experiência com sete casos de anastomoses mamária-artéria pulmonar, realizadas através de toracotomia direita (5) e esquerda (2), em pacientes portadores de tetralogía de Fallot (quatro femininos e três masculinos). A idade variou de dois a 63 meses (m = 18,4), com peso médio de 7,9 kg. Seis apresentavam graus variados de hipoplasia pulmonar. Houve dois óbitos pós-operatórios (1º e 2º dias), devidos a trombose da artéria mamária, no local de seu clampleamento. Dois pacientes foram submetidos a correção total (um mês e três anos após): no 1º (menina de 24 meses, 10 kg de peso), a anastomose foi feita pelas más condições gerais, apesar do bom tamanho das pulmonares. No 2º (menino de 15 meses, 8,1 kg, no qual uma operação de Blalock-Taussig clássica foi feita e trombosou no 3º mês de vida), foi possível observar o progressivo desenvolvimento das artérias pulmonares, por estudo hemodinâmico. Em ambos, o funcionamento da anastomose era perfeito e a correção foi bem sucedida. Três outros pacientes aguardam o momento oportuno para a correção final. Apesar do reduzido número e do curto tempo de observação, acredita-se que a anastomose mamáriapulmonar possa ser outra opção paliativa para os portadores de cardiopatias congênitas cianogênicas, com hipoplasia das artérias pulmonares e que os melhores resultados devam ser obtidos nos pacientes maiores, fora de situações de emergência e com pequenas artérias pulmonares.The systemic-pulmonary shunts are an important procedure to treat and prepare, for the final correction, cyanotic patients with hypoplastic pulmonary arteries. All of them have advantages and disadvantages, and the results will depend on the age and weight of the patients and the complexity of their heart disease. The present study reports seven internal mammary-pulmonary anastomosis, made through right (2) or left (5) thoracotomies, in patients with Tetralogy of Fallot and hypoplastic pulmonary arteries, from 2 to 63 months of age (m = 18,4) and mean weight of 7.9 kg. There were two deaths (1st and 2nd days), due to thrombosis of the internal mammary, where it was clamped. Two patients went to total correction (1 month and 3 years later). In the first case, the shunt was made due to the general conditions of the child, despite the good size of the pulmonary arteries. In the second case (a 15 months old boy, in whom a classical Blalock-Taussig shunt was made and thrombosed in the 3rd month of life) was possible to follow the progressive enlargement of the pulmonary arteries. In both the shunts were well functioning and the total correction was successful. Three patients are waiting for their best time for final procedures. Despite the small number and the short period of observations, the authors do believe that the internal mammary-pulmonary artery anastomisis is palliative option for these patients. The best results are obtained among the eldest children that are not in an emergency situation and not involving small pulmonary arteries

Implementation equations for HSn RF pulses

Implementation equations for the family of stretched hyperbolic secant (HS) pulses are derived in the linear adiabatic range for inversion of spins. These master equations provide convenience relations for relating the peak amplitude RF of the pulse to the frequency sweep (bwdth) range of the pulse and its duration T. The bandwidth of the pulse can also be related to the effective coverage (bw) of the pulse to a defined or chosen spectral region. The choice of pulse determined by the use of these derived expressions guarantees uniform inversion to a prescribed efficiency across the selected spectral region. The performance of HS pulses in determining the cut-off region between spectral regions was also examined. It is found that beyond a unique Tbwdth product no additional gain may be obtained by extending pulse durations for a chosen bwdth of pulse. An example of practical implementation of the inversion pulses is presented for adiabatic decoupling using HS and HS pulses. It is shown that despite added B inhomogeneity in the form of additional amplifier power to 400% from optimal, these pulses can still yield reproducible decoupled spectra