Two‐dimensional model of methane thermal decomposition reactors with radiative heat transfer and carbon particle growth

A two‐dimensional model of methane thermal decomposition reactors is developed which accounts for coupled radiative heat and polydisperse carbon particle nucleation, growth, and transport. The model uses the Navier–Stokes equations for the fluid dynamics, the radiative transfer equation for methane and particle species radiation absorption, the advection–diffusion equation for gas and particle species transport, and a sectional method for particle species nucleation, heterogenous growth, and coagulation. The model is applied to a tubular laminar flow reactor. The simulation results indicate the development of a reaction boundary layer inside the reactor, which results in significant variation of the local particle size distribution across the reactor. © 2011 American Institute of Chemical Engineers AIChE J, 58: 2545–2556, 2012     

Development of disease management recommendations for the durian and jackfruit industries in the Philippines using farmer participatory research

Promoting the adoption of improved technologies among smallholder farmers is a challenge faced by agricultural scientists and extension personnel around the world. In the southern Philippines, Phytophthora diseases severely affect the yields of durian and jackfruit. A limited understanding of these diseases among farmers and extension professionals compromises their effective management and significantly reduces yields. Recommended management interventions were rarely validated in field trials. A participatory research approach was used to collect information on current farming practices, identify industry constraints, and to develop and promote management strategies for smallholder durian and jackfruit growers. Farmers identified the development of effective disease management strategies as the highest priority so information on the biology, epidemiology and management of the suspected pathogen, Phytophthora, and other pests and diseases, was presented and discussed. Participants were then asked to propose and design research trials to diagnose the pathogen and to test simple management interventions on their crops. The trials were established and managed by participants and monitored by the group of growers, researchers and extension staff over 3 years. Responsibility for the on-farm trials encouraged participants to become directly involved in the research process, improving their skills in developing and critically assessing solutions for management of their orchards, and in decision-making processes. Results from the Participatory Action Research (PAR) trials were subjected to simple benefit-cost analyses and used to formulate a series of low-, medium- and high-input disease management packages. The low-input options included sanitation and manual pruning and weeding, and other activities requiring relatively low levels of time and financial investment. Medium- and high-input options required greater investment of time, resources and finances and included application of soil amendments, water management through construction of drainage channels and mounding, and the application of pesticides. The availability of a range of options facilitates the adoption of improved management by farmers from diverse backgrounds, resources and capacity.     

Pulsed field gel electrophoresis typing of human and retail foodstuff Campylobacters: an Irish perspective

Campylobacter enteritis is a zoonosis, an infectious disease transmissible under normal conditions from vertebrate animals to man, presenting a major global public health burden. In this study, Pulsed Field Gel Electrophoresis (PFGE) was employed to identify common genotypes in a collection of 600 Campylobacter isolates in order to investigate if profiles obtained from retail samples of foodstuffs matched genotypes causing illness in the community in Ireland. The Campylobacters were isolated from retail foodstuffs, and cases of gastroenteritis, over the same 20-month period in three population centres in Ireland. The major observation made was of a high level of PFGE-genotype heterogeneity; 236 SmaI discrete genotypes were found in 507 strains successfully analysed. Analysis of the PFGE profiles revealed 22 common profiles amongst food isolates and those causing enteritis in humans. These cojoint PFGE genotypes indicate that 56 (38%) of the human clinical isolates are genetically related to 129 (36%) of the food isolates. The identification of these recurrent PFGE types, in the sampled Campylobacter coli and Campylobacter jejuni populations, indicates that a high proportion of Campylobacter isolates found in foods of animal origin also occur in patients with symptoms of enteritis. This data adds weight to the epidemiological hypothesis that a high proportion of human Campylobacter cases are contracted via the handling and consumption of contaminated foodstuffs, in particular poultry.     

New huprine derivatives functionalized at position 9 as highly potent acetylcholinesterase inhibitors

A series of 24 huprine derivatives diversely functionalized at position 9 have been synthesized and evaluated for their inhibitory activity against human recombinant acetylcholinesterase (AChE). These derivatives were prepared in one to five steps from huprine 1 bearing an ester function at position 9. Ten analogues ( 1 , 2 , 6 – 9 , 13 – 15 , and 23 ) are active in the low nanomolar range (IC₅₀ <5 nM ), very close to the parent compound huprine X. Compounds 2 , 6 , and 7 show a very good selectivity for AChE, with AChE inhibitory activities 700–1160‐fold higher than those for butyrylcholinesterase (BChE). The inhibitory potency of these compounds decreases with the steric bulk of the substituents at position 9. According to docking simulations, small substituents fit into the acyl‐binding pocket, whereas the larger ones stick out of the active site gorge of AChE. Determination of the kinetic parameters of three of the most potent huprines ( 2 , 6 , and 7 ) showed that most of the difference in K_D is accounted by a decrease in k_on, which is correlated to the increase of the substituent size. A first in vivo evaluation has been performed in mice for the most active compound 2 (IC₅₀=1.1 nM ) and showed a rather weak toxicity (LD₅₀=40 mg kg^?1) and an ability to cross the blood–brain barrier with doses above 15 mg kg^?1.     

Access to new carbohydrate-functionalized polylactides via organocatalyzed ring-opening polymerization

The 4-dimethylaminopyridine (DMAP) catalyzed ring-opening polymerization of lactide using various carbohydrate initiators has been assessed for the functionalization of polylactide. Selectively protected glucose derivatives bearing a free primary alcohol (Glc-1r) and a free secondary alcohol (Glc-2r), glucose and cyclodextrin diol derivatives (Glc-diol and CD-diol), methyl-α-d-glucopyranoside (Glc-Me) and native β-cyclodextrin (CD) were used as initiators. According to the solubility of the carbohydrate derivative, the polymerizations were conducted in chlorinated solvents and in the bulk. Relatively narrow distributions are obtained in high yields in the absence of side reactions, affording a 100% functionalization efficiency. The catalytic synthesis of new carbohydrate link-functionalized polylactides and carbohydrate core star polylactides is reported.     

Bilayer systems of tantalum or zirconium nitrides and molybdenum for optimized diamond deposition

Thermo chemical computing validates the stability of different nitrides against Co, Mo, and methane up to 1150 K, showing the highest chemical stability against carburization for ZrN and TaN under static conditions.Single zirconium and tantalum nitrides layers have been sputtered onto WC-Co substrates as diffusion barriers and buffer layers under specific reactive sputtering conditions. To improve the nuclei density of diamond during CVD processing, a thin Mo extra layer has been added (< 500 nm). In this study, two bilayer systems have been tested: TaN-Mo and ZrN-Mo. Nano crystalline diamond has been grown under negative biased substrates.After diamond deposition, a massive carburization of molybdenum and tantalum nitride is observable whereas zirconium nitride is not. Nevertheless, a small amount of cobalt has migrated through the ZrN layer. The better efficiency of the ZrN layer to prevent diffusion of the Co element, leads to expect an increased adhesion of diamond on ZrN-Mo bilayer coating. A TEM study is done to improve understanding of phenomena occurring at the interfaces during process.     

Crystallographic Analysis of Martensite in 0.2C-2.0Mn-1.5Si-0.6Cr Steel using EBSD

The crystallography of martensite formed in 0.2C-2.0Mn-1.5Si-0.6Cr steel was studied using the electron backscattered diffraction(EBSD) technique.The results showed that the observed orientation relationship(OR) was closer to that of Nishiyama-Wassermann(N-W) than Kurdjumov-Sachs.The martensite consisted of parallel laths forming morphological packets.Typically,there were three different lath orientations in a morphological packet consisting of three specific N-W OR variants sharing the same {111} austenite plane.A packet of martensite laths with a common {111} austenite plane was termed a crystallographic packet.Generally,the crystallographic packet size corresponded to the morphological packet size,but occasionally the morphological packet was found to consist of two or more crystallographic packets.Therefore,the crystallographic packet size appeared to be finer than the morphological packet size.The relative orientation between the variants in crystallographic packets was found to be near 60 /<110>,which explains the strong peak observed near 60 in the grain boundary misorientation distribution.Martensite also contained a high fraction of boundaries with a misorientation in the range 2.5-8.Typically these boundaries were found to be located inside the martensite laths forming sub-laths.     

Experimental Evidence for Seed Metabolic Allometry in Barrel Medic (Medicago truncatula Gaertn.)

Seed size is often considered to be an important trait for seed quality, i.e., vigour and germination performance. It is believed that seed size reflects the quantity of reserve material and thus the C and N sources available for post-germinative processes. However, mechanisms linking seed size and quality are poorly documented. In particular, specific metabolic changes when seed size varies are not well-known. To gain insight into this aspect, we examined seed size and composition across different accessions of barrel medic (Medicago truncatula Gaertn.) from the genetic core collection. We conducted multi-elemental analyses and isotope measurements, as well as exact mass GC–MS metabolomics. There was a systematic increase in N content (+0.17% N mg⁻¹) and a decrease in H content (–0.14% H mg⁻¹) with seed size, reflecting lower lipid and higher S-poor protein quantity. There was also a decrease in ²H natural abundance (δ²H), due to the lower prevalence of ²H-enriched lipid hydrogen atoms that underwent isotopic exchange with water during seed development. Metabolomics showed that seed size correlates with free amino acid and hexoses content, and anticorrelates with amino acid degradation products, disaccharides, malic acid and free fatty acids. All accessions followed the same trend, with insignificant differences in metabolic properties between them. Our results show that there is no general, proportional increase in metabolite pools with seed size. Seed size appears to be determined by metabolic balance (between sugar and amino acid degradation vs. utilisation for storage), which is in turn likely determined by phloem source metabolite delivery during seed development.     

Visualization of Flow Patterns in Closed Loop Flat Plate Pulsating Heat Pipe Acting as Hybrid Thermosyphons under Various Gravity Levels

A particular flat plate pulsating heat pipe (FPPHP), filled with FC72, is tested during the 62^th and 64^th ESA parabolic flight campaigns under vertical orientation. The FPPHP is made of a thin copper plate, in which a curved channel disposed with 11 U-turns is milled and closed on the top face by a transparent borosilicate plate. The particular characteristics is that the equivalent hydraulic diameter of the square channel (2.5 × 2.5 mm²) is above the working fluid capillary diameter on ground, inducing a stratification of the liquid/vapor phases under ground and hyper-gravity conditions, whatever the orientation. The energy transfer mode in such conditions is represented either by pure pool boiling inside the channels almost completely filled by the liquid phase or by an annular flow pattern inside the channels mostly filled by the refrigerant vapor. Instead, during the microgravity phases, the fluid regime naturally turns into a slug-plug flow pattern. During the transition from 1.8 g to 0 g a rapid dry-out may occur in some of the channels, followed by a similarly fast reaction of liquid plugs moving towards the evaporator from the condenser zone. Such stop-and-start motion events continue during the whole microgravity period, leading to strong temperature oscillations, but also to a still acceptable thermal performance of the device.     

Unpacking Pandora from Its Box: Deciphering the Molecular Basis of the SARS-CoV-2 Coronavirus

An enigmatic localized pneumonia escalated into a worldwide COVID-19 pandemic from Severe Acute Respiratory Syndrome Coronavirus 2 (SARS-CoV-2). This review aims to consolidate the extensive biological minutiae of SARS-CoV-2 which requires decipherment. Having one of the largest RNA viral genomes, the single strand contains the genes ORF1ab, S, E, M, N and ten open reading frames. Highlighting unique features such as stem-loop formation, slippery frameshifting sequences and ribosomal mimicry, SARS-CoV-2 represents a formidable cellular invader. Hijacking the hosts translational engine, it produces two polyprotein repositories (pp1a and pp1ab), armed with self-cleavage capacity for production of sixteen non-structural proteins. Novel glycosylation sites on the spike trimer reveal unique SARS-CoV-2 features for shielding and cellular internalization. Affording complexity for superior fitness and camouflage, SARS-CoV-2 challenges diagnosis and vaccine vigilance. This review serves the scientific community seeking in-depth molecular details when designing drugs to curb transmission of this biological armament.