Slab waveguide photobioreactors for microalgae based biofuel production

Microalgae are a promising feedstock for sustainable biofuel production. At present, however, there are a number of challenges that limit the economic viability of the process. Two of the major challenges are the non-uniform distribution of light in photobioreactors and the inefficiencies associated with traditional biomass processing. To address the latter limitation, a number of studies have demonstrated organisms that directly secrete fuels without requiring organism harvesting. In this paper, we demonstrate a novel optofluidic photobioreactor that can help address the light distribution challenge while being compatible with these chemical secreting organisms. Our approach is based on light delivery to surface bound photosynthetic organisms through the evanescent field of an optically excited slab waveguide. In addition to characterizing organism growth-rates in the system, we also show here, for the first time, that the photon usage efficiency of evanescent field illumination is comparable to the direct illumination used in traditional photobioreactors. We also show that the stackable nature of the slab waveguide approach could yield a 12-fold improvement in the volumetric productivity.     

Optically induced microfluidic reconfiguration

Reconfigurable systems, like the field-programmable gate array in electronics, have numerous advantages including cost, adaptability, robustness, and security. Despite this, few other chip-based technologies have developed equivalently ubiquitous reconfiguration methods. As a first step to applying this paradigm to channel-based microfluidics, we present here a rapid optofluidic technique to create, move, and remove arbitrary solid regions in a microfluidic flow simply by illumination with an optical pattern. While other techniques have shown the ability to manipulate individual particles using spatial light modulation, we demonstrate here the ability to create reconfigurable flow pathways and build morphable channel structures. These structures can be modified on the order of seconds using a combined photothermal and thermo-rheological effect. In addition to characterizing the effect, we also apply this technique to create dynamic traps for biomolecules, and demonstrate trapping of λ-DNA molecules and nanoparticles, with a 25 fold suppression of diffusion.     

In situ electrochemical X-ray absorption spectroscopy of oxygen reduction electrocatalysis with high oxygen flux

An in situ electrochemical X-ray absorption spectroscopy (XAS) cell has been fabricated that enables high oxygen flux to the working electrode by utilizing a thin poly(dimethylsiloxane) (PDMS) window. This cell design enables in situ XAS investigations of the oxygen reduction reaction (ORR) at high operating current densities greater than 1 mA in an oxygen-purged environment. When the cell was used to study the ORR for a Pt on carbon electrocatalyst, the data revealed a progressive evolution of the electronic structure of the metal clusters that is both potential-dependent and strongly current-dependent. The trends establish a direct correlation to d-state occupancies that directly tracks the character of the Pt-O bonding present.     

非磁性替代原子对Ce2Co17居里温度和饱和磁化强度的影响

用真空电弧熔炼法制备了Ｃｅ２Ｃｏ１７－ｘＭｘ（Ｍ＝Ｇａ,Ａｌ和Ｓｉ）化合物。通过Ｘ射线衍射和磁性测量手段,研究了非磁性替代原子Ｇａ,Ａｌ和Ｓｉ的加入对Ｃｅ２Ｃｏ１７化合物的剧里温度和饱和磁化强度的影响,其中Ｓｉ在Ｃｅ２Ｃｏ１７化合物中的固溶度最小,并使居里温度和饱和磁化强度下降幅度最大。     

Observation of epithermal 2S muonium

A slow muon beam was passed through a thin aluminium foil and the emerging beam was studied for the presence of muonium in the 2S state. The fraction and the velocity distribution of the 2S muonium was determined.     

Time integration of the non-linear Galerkin method

e-mail: bosco{at}mac.cie.uva.es, frutos@mac.cie.uva.es Numerical tests are presented that, for the Kuramoto-Sivashinskyand a reaction-diffusion equation, compare the non-linear Galerkinmethod with standard pseudospectral and pure spectral Galerkindiscretizations. The results show that, for these problems,the non-linear Galerkin method is not competitive with eitherpure spectral Galerkin or pseudospectral discretizations.     

Exponential stability for a contact problem in thermoelasticity

We consider the unilateral problem for the thermoelastic equationand we show that the solution decays exponentially to zero astime goes to infinity; that is, denoting by E(t) the first-orderenergy of the system, we show that positive constants C and exist which satisfy E(t)CE(0)e^–$$$.     

Determination of boron and nitrogen in boron nitride

Improved techniques are described for the determination of boron and nitrogen in pure boron nitride. Controlled fusion of boron nitride with sodium carbonate in a muffle furnace is followed by a potentiometric titration of the boric acid. A special quartz vessel is described for the determination of nitrogen. The boron nitride is fused with sodium hydroxide and the resulting ammonia is swept into a receiver and titrated with standard hydrochloric acid. Boron and nitrogen values with their standard deviation are given for a typical pure boron nitride.     

龙爪芦荟和库拉索芦荟中微量锗的测定与红外光谱区别

采用吸光光度法对龙爪芦荟和库拉索芦荟中的微量锗进行了测定,并探讨了两种芦荟的红外光谱的区别。结果表明,龙爪芦荟中含锗量在26.1～28.6μg·g-1,回收率为91.6%～97 5%。库拉索芦荟中含锗量在16.8～20.0μg·g-1,回收率为87.1%～94.5%。两种芦荟的FT IR光谱图在2100cm-1处有明显差异,由此可区别两种芦荟。