Building on the recent coded-caching breakthrough by Maddah-Ali and Niesen, the work here considers the K -user cache-aided wireless multi-antenna symmetric broadcast channel with random fading and ...imperfect feedback, and analyzes the throughput performance as a function of feedback statistics and cache size. In this setting, this paper identifies the optimal cache-aided degrees-of-freedom (DoF) within a factor of 4, by identifying near-optimal schemes that exploit a new synergy between coded caching and delayed CSIT, as well as by exploiting the unexplored interplay between caching and feedback-quality. The DoF expressions reveal an initial gain due to current CSIT, and an additional gain due to coded caching, which is exponential in the sense that any linear decrease in the required DoF performance, allows for an exponential reduction in the required cache size. In the end, this paper reveals three new aspects of caching: a synergy between memory and delayed feedback, a tradeoff between memory and current CSIT, and a powerful ability to provide cache-aided feedback savings.
DNAzymes are catalytically active DNA molecules that are normally isolated through in vitro selection methods, among which RNA-cleaving DNAzymes that catalyze the cleavage of a single RNA linkage ...embedded within a DNA strand are the most studied group of this DNA enzyme family. Recent advances in DNA nanotechnology and engineering have generated many RNA-cleaving DNAzymes with unique recognition and catalytic properties. Over the past decade, numerous RNA-cleaving, DNAzymes-based functional probes have been introduced into many research areas, such as in vitro diagnostics, intracellular imaging, and in vivo therapeutics. This review focus on the fundamental insight into RNA-Cleaving DNAzymes and technical tricks for their intracellular and in vivo applications, highlighting the recent progress in the clinical trial of RNA-Cleaving DNAzymes with selected examples. The challenges and opportunities for the future translation of RNA-cleaving DNAzymes for biomedicine are also discussed.
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IZUM, KILJ, NUK, PILJ, PNG, SAZU, UL, UM, UPUK
Abstract
Unsymmetrical disulfides are widely found in the areas of food chemistry, pharmaceutical industry, chemical biology and polymer science. Due the importance of such disulfides in various ...fields, general methods for the nondirected intermolecular disulfuration of C-H bonds are highly desirable. In this work, the conversion of aliphatic C(sp
3
)-H bonds and aldehydic C(sp
2
)-H bonds into the corresponding C-SS bonds with tetrasulfides (RSSSSR) as radical disulfuration reagents is reported. The decatungstate anion (W
10
O
32
4−
) as photocatalyst is used for C-radical generation via intermolecular hydrogen atom transfer in combination with cheap sodium persulfate (Na
2
S
2
O
8
) as oxidant. Herein a series of valuable acyl alkyl disulfides, important precursors for the generation of RSS-anions, and unsymmetrical dialkyl disulfides are synthesized using this direct approach. To demonstrate the potential of the method for late-stage functionalization, approved drugs and natural products were successfully C-H functionalized.
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•Summarize the modification and functionalization of single ZIF-8 particles.•Assess the prospects of ZIF-8 composite in adsorption and photocatalytic.•Explain the mechanism of ZIF-8 ...composites in treating wastewater pollutants.•Role of the synthetic parameters in the performance of ZIF-8 composites.•Provide theoretical foundation and novel ideas for studies on MOF-based materials.
Zeolitic imidazolate framework-8 (ZIF-8), which consists of metal atom Zn and 2-methylimidazole, is a kind of typical MOF materials. The unique properties of ZIF-8 endue it superior adsorption capacity and good host ability for photocatalytic materials, which makes it be a high-profile material in the treatment of wastewater. However, ZIF-8 particles tent to aggregate together and result in the decrease of specific surface area. They also suffer from weak recyclability, as it is hard to separate them from water after removing pollutant. The newly emerging ZIF-8 composite materials solve the above problems, and are successfully applied in wastewater treatment. In this review, the current design and synthesis methods of ZIF-8 composites are systematically summarized. The recent research progress of ZIF-8 composites as adsorbents and photocatalysts to remove wastewater pollutants is critically introduced. Different factors affecting its efficiency and the mechanism of pollutant removal are also discussed. This review attempts to lay the mechanistic insight for the application of ZIF-8 composite in practical wastewater treatment and provides new ideas for constructing high-efficient ZIF-8 based adsorbent and photocatalyst. For the purpose of revealing the whole potentiality of ZIF-8 composite in pollutants removal and water regeneration, current challenges are introduced and future research directions are proposed at last.
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GEOZS, IJS, IMTLJ, KILJ, KISLJ, NLZOH, NUK, OILJ, PNG, SAZU, SBCE, SBJE, UILJ, UL, UM, UPCLJ, UPUK, ZAGLJ, ZRSKP
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•The formation, function and implication of structural defects in MOF are presented.•Synthetic strategy and characterization of MOF-based membranes are ...described.•Structure-performance of MOF-based membranes in water reclamation are correlated.•Current challenges and potentials of MOF-based membranes are discussed.
Metal-organic framework (MOF), which is composed of metal ions and bridged organic ligands, are one of the most high-profile materials currently, because their regular and tunable pore structures confer unique properties. In particular, MOF materials have attracted widespread attention in the field of membrane separation, wherein water-stable MOF membranes stand out especially in the field of wastewater treatment and water regeneration. This review critically summarizes the various design and synthesis strategies of bare MOF membranes and MOF composite membranes. The formation and function of the structural defects in MOF play important roles in the performance of MOF-based membrane. Different characterization techniques are discussed systematically, and the applications of MOF membranes in membrane filtration, membrane distillation, and membrane pervaporation are described. In order to uncover the full potential of MOF-based membranes in wastewater treatment and water regeneration, current challenges are detailed and future research directions proposed.
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GEOZS, IJS, IMTLJ, KILJ, KISLJ, NLZOH, NUK, OILJ, PNG, SAZU, SBCE, SBJE, UILJ, UL, UM, UPCLJ, UPUK, ZAGLJ, ZRSKP
A tandem process involving the dehydroaromatization of the terpene limonene and the hydrodeoxygenation of stearic acid has been found to be efficiently catalyzed by Pd-Ni/HZSM-5. The process involves ...the generation of p-cymene from terpene with concomitant formation of H2, which leads to the one-pot hydrodeoxygenation of stearic acid to C17 and C18 alkanes; these products can be used as kerosene additives for aviation fuel. Screening a wide range of catalysts, the bimetallic Pd-Ni/HZSM-5 catalyst is the most efficient, leading to quantitative conversion of stearic acid to alkanes in limonene at 280 °C at a H2 pressure of 2 bar after 120 min. It has been found that single Ni or Pd catalysts lead to a poor conversion of stearic acid in limonene at a H2 pressure of 2 bar. The combination of physically mixed Pd- and Ni-sites onto different supports (Pd/HZSM-5 or Pd/C, and Ni/HZSM-5, Ni/HY, or Ni/HBEA) leads to catalysts which show satisfactory conversion to p-cymene but generally have very low stearic acid conversion rates. Directly incorporating Pd and Ni onto the HZSM-5 scaffold forms the Pd-Ni/HZSM-5 bimetallic catalyst, which demonstrates a remarkable improvement in stearic acid conversion to C17 and C18 alkane products. In this catalyst system, Pd is shown to be the active site for limonene dehydroaromatization, while Ni catalyzes the separate stearic acid hydrodeoxygenation. The acidity of HZSM-5 (modified by the Si/Al ratios) influences the performance of the Pd-Ni bimetallic catalyst, and the proper pore size of HZSM-5 prevents side-reactions from limonene condensation. In addition, the alloyed Pd-Ni nanoparticles (optimized with higher Pd/Ni ratios) on the external surface of HZSM-5 enhance internal H• transfer between the two metals, thereby increasing the rate of stearic acid hydrodeoxygenation. The catalytic compatibility of the Pd and Ni sites, coupled with the proper pore sizes and optimized level of Brönsted acid sites in HZSM-5, result in the design of a multifunctional catalyst that is efficient for both steps of the cascade reaction. Hence, a bimetallic 5%Pd-10%Ni/HZSM-5 catalyst has been developed that allows for a simple approach for producing aromatics and hydrocarbon components present in biojet fuel derived from two biomass resources.
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IJS, KILJ, NUK, PNG, UL, UM
A new approach for identifying moving loads is proposed in which one can identify continuous or discontinuous loads from the response data by using a local linear embedding algorithm. This approach ...is especially well suited for moving loads that are difficult to measure directly and it does not depend on modeling the structures. Four simulated examples are conducted on a 5-m beam with four types of moving loads and the results verify the usefulness of our approach, but there is a small amount of distortion at some stages. The robustness of the approach is further verified by contaminating the response data with white noise of different levels, and the results show that the approach mentioned in this paper has good robustness. This identification approach for moving loads can be applied to aerospace engineering applications.
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NUK, OILJ, SAZU, UKNU, UL, UM, UPUK
Gouging is a large nonlinear deformation phenomenon experienced in rail materials under severe loading conditions such as the tremendous heating caused by frictional effects at the slider/rail ...interface. The material point method (MPM) algorithm is designed specifically to solve such nonlinear, large deformation problems. The theories and steps of the MPM algorithm are described in this paper, and an investigation of hypervelocity gouging is conducted using the MPM algorithm. Because of frictional heating near the contact region, the effects of temperature on the gouge development are evaluated by several developed thermal environment scenarios. Moreover, the regular patterns of gouging at various impact velocities, horizontal velocities, and friction coefficients are analyzed. The results show that the MPM algorithm can successfully simulate the gouging phenomenon. With the gouge initiation and development, the temperature rapidly increases to the melting temperature, and the yield stress rapidly decreases at the gouge location. The regular patterns of gouging provide a new effective method for antigouging research.
Abstract
Background
The coronavirus disease 2019 (COVID-19) pandemic has led to global research to predict those who are at greatest risk of developing severe disease and mortality. The aim of this ...meta-analysis was to determine the associations between obesity and the severity of and mortality due to COVID-19.
Methods
We searched the PubMed, EMBASE, Cochrane Library and Web of Science databases for studies evaluating the associations of obesity with COVID-19.
Odds ratios (ORs) and 95% confidence intervals (CIs) were calculated using random- or fixed-effects models. Meta-regression analyses were conducted to estimate regression coefficients.
Results
Forty-six studies involving 625,153 patients were included. Compared with nonobese patients, obese patients had a significantly increased risk of infection.
(OR 2.73, 95% CI 1.53–4.87;
I
2
= 96.8%), hospitalization (OR 1.72, 95% CI 1.55–1.92;
I
2
= 47.4%), clinically severe disease (OR 3.81, 95% CI 1.97–7.35;
I
2
= 57.4%), mechanical ventilation (OR 1.66, 95% CI 1.42–1.94;
I
2
= 41.3%), intensive care unit (ICU) admission (OR 2.25, 95% CI 1.55–3.27;
I
2
= 71.5%), and mortality (OR 1.61, 95% CI 1.29–2.01;
I
2
= 83.1%).
Conclusion
Patients with obesity may have a greater risk of infection, hospitalization, clinically severe disease, mechanical ventilation, ICU admission, and mortality due to COVID-19. Therefore, it is important to increase awareness of these associations with obesity in COVID-19 patients.
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DOBA, IZUM, KILJ, NUK, PILJ, PNG, SAZU, SIK, UILJ, UKNU, UL, UM, UPUK
Acetic acid is an important bulk chemical that is currently produced via methanol carbonylation using fossil based CO. Synthesis of acetic acid from the renewable and cheap CO2 is of great ...importance, but state of the art routes encounter difficulties, especially in reaction selectivity and activity. Here we report a route to produce acetic acid from CO2, methanol and H2. The reaction can be efficiently catalysed by Ru-Rh bimetallic catalyst using imidazole as the ligand and LiI as the promoter in 1,3-dimethyl-2-imidazolidinone (DMI) solvent. It is confirmed that methanol is hydrocarboxylated into acetic acid by CO2 and H2, which accounts for the outstanding reaction results. The reaction mechanism is proposed based on the control experiments. The strategy opens a new way for acetic acid production and CO2 transformation, and represents a significant progress in synthetic chemistry.
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