A Rare Presentation of Crohn's Disease

Free peritoneal perforation is a rare complication of Crohn's disease with a report of only 100 cases in the literature. It needs an emergency exploration and an unaware general surgeon is confounded in intraoperative decision-making. We present our experience when this rarity struck us in a district hospital and briefly review the guidelines of optimal management of this complication of Crohn's disease

Efficient and environmentally friendly microwave-assisted synthesis of catalytically active magnetic metallic Ni nanoparticle

Pure magnetic metallic nickel was synthesized by a simple and fast microwave-assisted method using a monomode microwave reactor. Nickel chloride was employed as metal precursor, while an environmental-friendly mixture of ethylene glycol and ethanol was simultaneously used as solvent and reducing agent. The parameters combination, for the occurrence of the reaction, of the mixture molar fraction, and the metal precursor concentration was developed. The influence of the temperature and the time of the irradiation was investigated. The best performance (71% yield) was achieved at 250 °C in 5 min of microwave irradiation. The phase and the morphology of the metal were analyzed by X-ray diffraction, scanning emission microscopy, and transmission electron microscopy, while the surface area was determined by nitrogen physisorption. The material exhibited a strong magnetic behavior. The metallic nickel showed high catalytic activity for the hydrogenolysis of benzyl phenyl ether, a lignin model compound, in a microwave-assisted environmental-friendly reaction

Catalytic Conversion of Biomass

Petroleum, natural gas and coal supply most of the energy consumed worldwide and their massive utilization has allowed our society to reach high levels of development in the past century. The shift towards a bio-based economy has been recently promoted with ambitious targets to replace an important fraction of fossil fuels by renewable sources within 20 years. Biomass emerged as a highly suitable alternative for this bio-based revolution as an ideal substitute for petroleum in the production of fuels, chemicals and carbon-based materials. Consequently, a number of ongoing efforts have been devoted to biomass conversion/valorization towards valuable products using a number of (bio)catalytic strategies. Based on these premises, the present Special Issue of Catalysts was aimed to provide a number of broad and multifaceted contributions in the field of catalytic biomass conversion towards the production of high added value products from sugars (hemicellulose and cellulose fraction) and lignin as well as related biomass conversion strategies. In this regard, Song et al. contributed to develop an efficient dehydration of fructose to HMF using heteropolyacid salts [1]. Along similar lines, two additional contributions for the Special Issue from Li et al. [2] and Fachri et al. [3] disclosed the catalytic aqueous conversion of glucose and inulin into HMF using Lewis acid and metal salts catalysts, respectively, providing also interesting modelling insights into the proposed chemistries. The produced furanic derivatives in these contributions as well as related compounds (e.g., sorbitol) have also promising prospects to be further upgraded to fuel components for blends. Pizzi et al. provided a nice approach towards high throughput screening of a range of heterogeneous catalysts for the conversion of furfural to bio-based fuel components [4] in a similar way to the approach proposed by Iglesias et al. for the conversion of furfural to furfuryl alcohol via Meerwein-Ponndorf-Verley reduction using Zr-SBA-15 [5], while valuable jet-fuel range hydrocarbons could also be produced from biomass-derived sorbitol using Ni-HZSM-5/SBA-15 catalysts [6]. Such biomass-engineered products have a significant potential to replace current petroleum-derived analogues with improved biocompatibility and a reduced environmental footprint. Levulinic acid and levulinates are related interesting platform molecules that can be derived from biomass and subsequently upgraded towards chemicals and biofuel precursors. Along these lines, Wang et al. proposed the utilization of cheap and environmentally friendly Nb/Al oxide catalysts for the conversion of kiwifruit waste to levulinic acid [7]. Additionally, the direct conversion of carbohydrates into ethyl levulinate using potassium phosphotungstate as efficient catalyst was reported by Zhao et al. [8]. Further conversion of levulinic acid to gamma-valerolactone (GVL) could also take place efficiently on nickel/alumina catalysts [9]. Hydrogenation and hydrodeoxygenation of lignin and lignocellulosic pyrolysis has also been another hot topic in recent times due to the possibility to produce aromatics and cyclic derivatives from biomass. Yi et al. proposed a highly efficient hydrogenation of lignin derived monophenols towards cyclohexanols using Pd/alumina catalysts [10]. Co-pyrolysis behavior of cotton straw mixtures and their catalytic hydrodeoxygenation were also investigated by Hua et al. [11] using Ni-Mo/alumina catalysts. Additional contributions to the Special Issue included the selective production of aromatics from 2-octanol on Zn-exchanged MFI zeolites [12], the electrocatalytic oxidation of cellulose to gluconate on carbon aerogel supported gold nanoparticles anodes [13] and the steam reforming of bioethanol to hydrogen catalyzed by Co/ceria catalysts [14]. The Guest Editors sincerely hope that the results presented as part of this Special Issue of most varied topics can serve as a starting point for further innovations in the catalytic conversion of biomass and look forward to enjoying further improvements in the aforementioned topics and fields in the future

SAR-Based Vibration Estimation Using the Discrete Fractional Fourier Transform

A vibration estimation method for synthetic aperture radar (SAR) is presented based on a novel application of the discrete fractional Fourier transform (DFRFT). Small vibrations of ground targets introduce phase modulation in the SAR returned signals. With standard preprocessing of the returned signals, followed by the application of the DFRFT, the time-varying accelerations, frequencies, and displacements associated with vibrating objects can be extracted by successively estimating the quasi-instantaneous chirp rate in the phase-modulated signal in each subaperture. The performance of the proposed method is investigated quantitatively, and the measurable vibration frequencies and displacements are determined. Simulation results show that the proposed method can successfully estimate a two-component vibration at practical signal-to-noise levels. Two airborne experiments were also conducted using the Lynx SAR system in conjunction with vibrating ground test targets. The experiments demonstrated the correct estimation of a 1-Hz vibration with an amplitude of 1.5 cm and a 5-Hz vibration with an amplitude of 1.5 mm

Clutter Suppression via Hankel Rank Reduction for DFrFT-Based Vibrometry Applied to SAR

Hankel rank reduction (HRR) is a method that, by prearranging the data in a Hankel matrix and performing rank reduction via singular value decomposition, suppresses the noise of a time-history vector comprised of the superposition of a finite number of sinusoids. In this letter, the HRR method is studied for performing clutter suppression in synthetic aperture radar (SAR)-based vibrometry. Specifically, three different applications of the HRR method are presented. First, resembling the SAR slow-time signal model, the HRR method is utilized for separating a chirp signal immersed in a sinusoidal clutter. Second, using simulated airborne SAR data with 10 dB of signal-to-clutter ratio, the HRR method is applied to perform target isolation and to improve the results of an SAR-based vibration estimation algorithm. Finally, the vibrometry approach combined with the HRR method is validated using actual airborne SAR data