Energy efficiency of mmWave massive MIMO precoding with low-resolution DACs

With the congestion of the sub-6 GHz spectrum, the interest in massive multiple-input multiple-output (MIMO) systems operating on millimeter wave spectrum grows. In order to reduce the power consumption of such massive MIMO systems, hybrid analog/digital transceivers and application of low-resolution digital-to-analog/analog-to-digital converters have been recently proposed. In this work, we investigate the energy efficiency of quantized hybrid transmitters equipped with a fully/partially-connected phase-shifting network composed of active/passive phase-shifters and compare it to that of quantized digital precoders. We introduce a quantized single-user MIMO system model based on an additive quantization noise approximation considering realistic power consumption and loss models to evaluate the spectral and energy efficiencies of the transmit precoding methods. Simulation results show that partially-connected hybrid precoders can be more energy-efficient compared to digital precoders, while fully-connected hybrid precoders exhibit poor energy efficiency in general. Also, the topology of phase-shifting components offers an energy-spectral efficiency trade-off: active phase-shifters provide higher data rates, while passive phase-shifters maintain better energy efficiency.Comment: Published in IEEE Journal of Selected Topics in Signal Processin

Nanostructured Chitosan-Based Biomaterials for Sustained and Colon-Specific Resveratrol Release

In the present work, we demonstrate the preparation of chitosan-based composites as vehicles of the natural occurring multi-drug resveratrol (RES). Such systems are endowed with potential therapeutic effects on inflammatory bowel diseases (IBD), such as Crohn’s disease (CD) and ulcerative colitis, through the sustained colonic release of RES from long-lasting mucoadhesive drug depots. The loading of RES into nanoparticles (NPs) was optimized regarding two independent variables: RES/polymer ratio, and temperature. Twenty experiments were carried out and a Box–Behnken experimental design was used to evaluate the significance of these independent variables related to encapsulation efficiency (EE). The enhanced RES EE values were achieved in 24 h at 39 °C and at RES/polymer ratio of 0.75:1 w/w. Sizes and polydispersities of the optimized NPs were studied by dynamic light scattering (DLS). Chitosan (CTS) dispersions containing the RES-loaded NPs were ionically gelled with tricarballylic acid to yield CTS-NPs composites. Macro- and microscopic features (morphology and porosity studied by SEM and spreadability), thermal stability (studied by TGA), and release kinetics of the RES-loaded CTS-NPs were investigated. Release patterns in simulated colon conditions for 48 h displayed significant differences between the NPs (final cumulative drug release: 79–81%), and the CTS-NPs composites (29–34%)

Quasi-Lie schemes and Emden--Fowler equations

The recently developed theory of quasi-Lie schemes is studied and applied to investigate several equations of Emden type and a scheme to deal with them and some of their generalisations is given. As a first result we obtain t-dependent constants of the motion for particular instances of Emden equations by means of some of their particular solutions. Previously known results are recovered from this new perspective. Finally some t-dependent constants of the motion for equations of Emden type satisfying certain conditions are recovered

Accretion and photodesorption of CO ice as a function of the incident angle of deposition

Non-thermal desorption of inter- and circum-stellar ice mantles on dust grains, in particular ultraviolet photon-induced desorption, has gained importance in recent years. These processes may account for the observed gas phase abundances of molecules like CO toward cold interstellar clouds. Ice mantle growth results from gas molecules impinging on the dust from all directions and incidence angles. Nevertheless, the effect of the incident angle for deposition on ice photo-desorption rate has not been studied. This work explores the impact on the accretion and photodesorption rates of the incidence angle of CO gas molecules with the cold surface during deposition of a CO ice layer. Infrared spectroscopy monitored CO ice upon deposition at different angles, ultraviolet-irradiation, and subsequent warm-up. Vacuum-ultraviolet spectroscopy and a Ni-mesh measured the emission of the ultraviolet lamp. Molecules ejected from the ice to the gas during irradiation or warm-up were characterized by a quadrupole mass spectrometer. The photodesorption rate of CO ice deposited at 11 K and different incident angles was rather stable between 0 and 45$^{\circ}$. A maximum in the CO photodesorption rate appeared around 70$^{\circ}$-incidence deposition angle. The same deposition angle leads to the maximum surface area of water ice. Although this study of the surface area could not be performed for CO ice, the similar angle dependence in the photodesorption and the ice surface area suggests that they are closely related. Further evidence for a dependence of CO ice morphology on deposition angle is provided by thermal desorption of CO ice experiments

Quantum Lie systems and integrability conditions

The theory of Lie systems has recently been applied to Quantum Mechanics and additionally some integrability conditions for Lie systems of differential equations have also recently been analysed from a geometric perspective. In this paper we use both developments to obtain a geometric theory of integrability in Quantum Mechanics and we use it to provide a series of non-trivial integrable quantum mechanical models and to recover some known results from our unifying point of view

Acute occupational phosphine intoxications : a retrospective study by the Belgian Poison Centre

C

Análise da melhor alternativa terapêutica para malformações arteriovenosas durais intracranianas

The material for this research consisted of 93 patients with dural arteriovenous malformations (DAVMs) who were studied retrospectively with regards to therapeutic success and failure, who had undergone either neurosurgery, or embolization or a combination of both methods and whose disease was located in the cavernous sinus, the superior sagittal sinus, the transverse-sigmoid sinus of the anterior fossa and the tentorium. Thus, it was possible to arrive at the following conclusions: treatment of the DAVMs must be indicated, jointly, by an interventionist neuroradiologist and a neurosurgeon; DAVMs of the transverse-sigmoid sinus were better treated when a combination of both methods was used; DAVMs of the tentorium were also better treated with a combined method; the endovascular method ensured only a 50% chance of therapeutic success for DAVMs of the superior sagittal sinus; DAVMs of the cavernous sinus are better treated when the endovascular method was used with a transvenous approach, relative to the transarterial approach.O material utilizado consistiu de 93 pacientes portadores de malformações arteriovenosas durais (MAVDs) estudados retrospectivamente em relação ao sucesso e ao fracasso terapêutico submetidos aos métodos neurocirúrgico ou endovascular ou, ainda, combinação entre ambos, em que a doença se localizou nas regiões do seio cavernoso, do seio sagital superior, do seio transverso-sigmóide, da fossa anterior e do tentório. As conclusões foram as seguintes: o tratamento das MAVDs deve ser indicado pelo neurorradiologista intervencionista e pelo neurocirurgião, conjuntamente; as MAVDs do seio transverso-sigmóide foram melhor tratadas através do método combinado; as MAVDs do tentório foram melhor tratadas através do método combinado; as MAVDs do seio sagital superior tratadas por método endovascular asseguraram apenas 50% de sucesso terapêutico; as MAVDs do seio cavernoso são melhor tratadas por método endovascular empregando-se a via transvenosa quando comparadas com a via transarterial.Universidade Federal de São Paulo (UNIFESP), Escola Paulista de Medicina (EPM)Institute of GoiâniaUniversity of São PauloUNIFESP, EPMSciEL