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In this paper, heat transfer characteristics of phase change material in rectangular containers are numerically analyzed. The inclination angles of the container refer to 0°, 90°, and 180°. Both theoretical and practical periodic temperature boundary conditions are taken into consideration, in which the periodic temperature boundary conditions include 50-80 °C and 65-80 °C. The comparison study is carried out through the liquid fraction and temperature histories during the heat transfer process under these different boundary conditions. It is indicated that there are large differences between the calculated results under the theoretical and the practical periodic temperature boundary conditions when the temperature boundary is 50-80 °C, while the theoretical and the practical periodic temperature boundary conditions of 65-80 °C have relatively little effect on the numerical results of the heat transfer process of the phase change material. Furthermore, compared with the temperature increasing stage, the numerical results calculated under the theoretical and the practical boundary conditions have more significant differences in the temperature decreasing stage. The research conclusion of this paper can provide a theoretical basis for the application of phase change material under periodic temperature boundary conditions. [ABSTRACT FROM AUTHOR]

• SOC stability was determined using TG50 and DSC. • SOC stability decreased with the elevation at p < 0.05 level. • SOC stability was controlled by TP, alkanes, Mn, Th, aliphatic, lignin, and phenol. • Soil nutrients and molecular features but not minerals controlled SOC stability. The mechanisms that maintain soil organic carbon (SOC) stability along the elevation gradient has not been adequately explored in mountain ecosystems, though numerous work has been performed to reveal potential impacts of multiple environmental factors on SOC stability. The objective of this study was to decipher the predominant factor and effects that affected SOC stability by linking elevation, soil nutrients, minerals, and chemical molecular composition with SOC thermal stability in Changbai Mountain (CBM), Northeast China. Results indicated that SOC ranged from 2.12% to 17.75% without obvious elevation dependency. SOC stability was evaluated using the temperature at which haft of the exothermic mass loss (TG50). The TG50 decreased with elevation at p < 0.05 level. SOC did not vary significantly across soils from predominant plant communities, which were the mixed coniferous and broad-leaved forests (HJL), mixed coniferous forests (ZYL), birch forests (YHL), and tundra vegetation zones (TYD). Total phosphorus (P) and manganese (Mn) differed significantly among these four zones. Aliphatic, alkanes, alkenes, and aromatics were predominant moieties of pyrolytic products of SOC in all zones. TP, alkanes, Mn, Th, aliphatic, Lg, and Ph were the main drivers controlling SOC in contents and stabilities. Mineral protection in conjunction with soil nutrients could explain 73% of the total variance in SOC stability, while Mn had more importance than Fe in stabilizing organic carbon in CBM. The structural equation model revealed positive effects of both mineral protection and molecular feature on SOC pool and stability. [ABSTRACT FROM AUTHOR]

Cultivation of marshes (Ma) to arable like pasture (Pa) and sugarcane (Sa) usually causes soil organic carbon (SOC) pool depletion within a short time. However, there are some uncertainties about which molecular composition of soil organic matter (SOM) is sensitive to land use change (LUC). In the present work, molecular components of SOM were investigated and compared to better understand the impacts of LUC on the carbon cycle from Ma to Pa or Sa in Louisiana and Florida. Pyrolysis-gas chromatography/mass spectrometry (Py-GC/MS) analysis indicated that LUC greatly altered the molecular composition of SOM. More lignin, polysaccharide, and phonetic compounds were founded from Ma, and more nitrogen-containing compounds were identified from Sa. Lignin and phenolic compounds had unexpectedly the most decrease from native marsh-sugarcane/pasture transitions, showing the same trend as SOC. This meant that lignin and phenol were not as stable as expected when undergoing LUC. LUC significantly yield more molecular moieties and then resulted in higher complexities and diversities of molecular components in Pa or Sa than those in Ma. Principal component analysis implied higher contributions of old carbon to SOM in Ma, and fresh biomass input contributed more SOM in Sa. Our results implied that human activities such as LUC could not only alter carbon fluxes but also simultaneously change molecular mechanisms that drive the carbon cycle. • Land use change has greatly altered the molecular composition of SOM. • Reclamation of marshes to sugarcane increased the chemical complexity of SOM. • Lignin and phonetic compounds were depleted when marsh changed to sugarcane. [ABSTRACT FROM AUTHOR]

Abstract  Synchronization of the Na/K pump molecules in a cell membrane was studied in frog skeletal muscle fibers using double Vaseline-gap voltage-clamp techniques. We found that the pumping rate of naturally random-paced pump molecules can be artificially synchronized by a pulsed, symmetric, oscillating membrane potential with a frequency comparable to the physiological turnover rate. The synchronized pump currents show separated outward and inward components, where the magnitude of the outward component is about three times the randomly-paced pump currents, and the magnitude-ratio of the outward to inward pump currents is close to 3:2, which reflects the stoichiometric ratio of the pump molecules. Once synchronized, the pumping rate is restricted to the field frequency, and the pump currents are mainly dependent on the field frequency, but not the field strength. In contrast to previous work, which by restraining the pumps at a presteady state succeeded in triggering the steps of the pump cycle only individually and between interruptions, here we synchronize the pumps running continuously and in a normal running mode. [ABSTRACT FROM AUTHOR]

Abstract  We studied entrainment of the catalytic cycle of the Na/K pumps by an imposed external AC electric field. Our results show that a well designed dichotomous oscillating electric field with a frequency close to the pumps’ natural turnover rate can synchronize the pump molecules. Characteristics of the synchronized pumps include: (1) outward pump currents responding to Na-extrusion and inward pump currents responding to K-pumping in are separated; (2) magnitude of the outward pump currents can be up to three times higher than that of the randomly paced pump currents; (3) magnitude ratio of the outward over inward pump currents reveals the 3:2 stoichiometry of the pumps. We, further, gradually increased the field oscillating frequency in a stepwise pattern and kept pump synchronization in each step. We found that the pumps’ turnover rate could be modulated up as the field frequency increased. Consequently, the pump currents significantly increased by many fold. In summary, these results show that the catalytic cycle of Na/K pumps can be synchronized and modulated by a well designed oscillating electric field resulting in activation of the pump functions. [ABSTRACT FROM AUTHOR]

Abstract: Effects of imposed large supraphysiological transmembrane potential (TP) pulses on channel proteins, particularly on the voltage-gated Na channels, were investigated. Voltage clamp techniques were used to deliver both shock and stimulation pulses, and to monitor changes in the channel functions. Our experimental results indicated that more than one 4ms duration TP shock of −450mV resulted in electroconformational denature of voltage-gated Na channels. This resulted in functional reductions in muscle cells’ excitability. We quantified the TP shock-induced decrease in the Na channel currents, compared the pre- and post-shocked Na channel currents’ voltage dependency, and studied the reversibility of the electroconformationally denatured ion channel proteins. These observations are particularly relevant to the problem of explaining the neuromuscular damage following high voltage electrical shock injuries despite no evidence of a thermal injury component. [Copyright &y& Elsevier]

Synthetic strategies for preparing N,N′-bridged oligomeric guanidines bearing peptide side chains both on solid support and in solution are presented. Monomers are prepared from common a-amino acids and therefore contain conventionally protected peptide side chains. The side chains include alkyl, aromatic, hydroxyl, amino, carboxylic acid, and amide functional groups. Oligomer elongation utilizes acid-sensitive sulfonyl activated thiourea through the formation of carbodiimide intermediate. With proper preparation of monomers, synthesis of oligomer can be performed in two directions (equivalent to N to C terminal or C to N terminal in a peptide sequence) with excellent efficiency. [ABSTRACT FROM AUTHOR]

Large cyclic decapeptides (up to 50-atom ring) were synthesized efficiently on the solid phase with allylester protection of the carboxyl terminus during elongation. Pentavalent ligands, in a “core-linker-finger” modular setup, were assembled by using these cyclic peptide cores to demonstrate large affinity gains for inhibition of surface receptor binding by the cholera toxin B pentamer. The results suggest that the peptide cores retain expanded conformation in solution so that shorter flexible linkers are needed for larger peptide cores to achieve the best inhibitory results. [ABSTRACT FROM AUTHOR]

The structure-based design of multivalent ligands offers an attractive strategy toward high affinity protein inhibitors. The spatial arrangement of the receptor-binding sites of cholera toxin, the causative agent of the severe diarrheal disease cholera and a member of the AB[sub 5] bacterial toxin family, provides the opportunity of designing branched multivalent ligands with 5-fold symmetry. Our modular synthesis enabled the construction of a family of complex ligands with five flexible arms each ending with a bivalent ligand. The largest of these ligands has a molecular weight of 10.6 kDa. These ligands are capable of simultaneously binding to two toxin B pentamer molecules with high affinity, thus blocking the receptor-binding process of cholera toxin. A more than million-fold improvement over the monovalent ligand in inhibitory power was achieved with the best branched decavalent ligand. This is better than the improvement observed earlier for the corresponding nonbranched pentavalent ligand. Dynamic light scattering studies demonstrate the formation of concentration-dependent unique 1:1 and 1:2 ligand/toxin complexes in solution with no sign of nonspecific aggregation. This is in complete agreement with a crystal structure of the branched multivalent ligand/toxin B pentamer complex solved at 1.45 Å resolution that shows the specific 1:2 ligand/toxin complex formation in the solid state. These results reiterate the power of the structure-based design of multivalent protein ligands as a general strategy for achieving high affinity and potent inhibition. [ABSTRACT FROM AUTHOR]

Chemical fertilizers and pesticides used are currently increasing alongside the human population grew and agriculture spread, resulting in high nitrogen (TN) and phosphorus (TP) contents in farmland soil and the surrounding water-bodies. Fabricating economic but effective metal impregnated biochar, as a sorbent to remove inorganic pollutants from water, is important to prevent eutrophication. In the present work, iron-loaded biochar was prepared by impregnating by FeCl 3 and following pyrolyzing at 550 °C. The chemical functional groups, surface morphologies, and internal crystal structures of the Fe-loaded biochar (Fe B) were characterized by Fourier transform infrared spectroscopy (FT-IR), scanning electron microscopy (SEM), and X-ray diffraction, respectively. Results indicated that the preparing process induced a layer of Fe oxide at the surface of biochar, and changed the surface morphology and internal crystal structure. The FeCl 3 content in soaking solution had remarkable effects on pore structure formation, surface morphology features and removal efficiencies of TN and TP from wastewater by biochar. The Langmuir model indicated that 1%-Fe impregnated biochar (B1) and the 10%-Fe impregnated biochar (B10) exhibited maximum adsorption capacity of TN and TP, which reached to more than 14 mg/g for TN and 90 mg/g for TP, respectively. B10 could remove over 85% of TP from artificial wastewater and less than 0.5% of TP was released in desorption experiments. Similarly, B1 could remove 60% of TN while only 1% was released in desorption experiments. B1 and B10 could remove 50% of TN and 80% of TP from the actual agricultural wastewater, respectively. This confirmed that Fe-impregnated biochar could effectively remove inorganic nutrients from wastewater and seal them in the prevention of secondary pollution. The Fe B was characterized by FT-IR and SEM before and after its application as an adsorbent in agricultural wastewater, and results revealed that the removal of TN and TP was primarily attributed to the well-developed pore structure and the Fe oxides fixed on the surface of biochar. Inorganic nitrogen and phosphorus in wastewater are removed by surface complexation, coprecipitation, electrostatic interaction and ion exchange. In conclusion, the present work demonstrated that the Fe B is an effective adsorbent for removing TN and TP pollutants from nutrient-rich wastewaters. [ABSTRACT FROM AUTHOR]

The design of high-affinity protein ligands is of fundamental interest in biomedical research. Often, one multivalent ligand and one multivalent protein are involved in such studies. Another area of ligand design concerns the so-called chemical inducer of dimerization, where one bifunctional ligand can bind two different proteins simultaneously and affect biological pathways. In such cases, three entities are to be considered in the binding event--one bifunctional ligand and two separate and different target protein molecules. However, these interactions generally involve only a single binding site on each target protein.

Currently, little is available on how mercury (Hg) methylation couples with soil organic matter decomposition in degraded permafrost in high northern latitudes, where the climate is becoming warmer rapidly. Here, we revealed the complex interactions between soil organic matter (SOM) mineralization, dissolved organic matter (DOM) and methylmercury (MeHg) production based on an 87-day anoxic warming incubation experiment. Results supported remarkably promotion effects of warming on MeHg production, by 130%–205% on average. Total mercury (THg) loss under warming treatment depended on marsh types but showed an increasing trend on the whole. Warming yielded higher proportions of MeHg to THg (%MeHg), increased by 123%–569%. As expected, greenhouse gas emission was significantly enhanced by warming. Warming also strengthened fluorescence intensities of fulvic-like and protein-like DOM, with contributions to total fluorescence intensities of 49%–92% and 8%–51%, respectively. DOM and its spectral features explained 60% variation of MeHg, and the explanation increased to 82% in conjunction with greenhouse gas emissions. The structural equation model implied that warming, greenhouse gas emission, and humification of DOM had positive effects on Hg methylation potential, while microbial-derived DOM showed negative effects on MeHg. These results showed that accelerated Hg loss and increased methylation covaried with greenhouse gas emission and DOM formation under warming conditions in permafrost marsh. By stimulating greenhouse gas emission and altering fluorescence features of dissolved organic matter, warming remarkably fueled MeHg production and triggered mercury loss in permafrost marsh soils in Northeast China. [Display omitted] • Warming promotes MeHg contents by 130%–205% in permafrost soils. • Warming causes more Hg loss and increased methylation covarying with SOM mineralization. • DOM and its spectral features predominate MeHg variation under warming. [ABSTRACT FROM AUTHOR]

An efficient synthesis of N,N'-substituted guanidine derivatives was developed via an aromatic sulfonylactivated thiourea intermediate. The use of certain aromatic sulfonamides, such as PbfNH[sub 2], as the key reagent to incorporate a TFA-labile guanidine protection group greatly facilitates solid-phase synthesis of N,N'-substituted guanidine compounds. [ABSTRACT FROM AUTHOR]

Background: Early differential diagnosis of coronavirus disease 2019 (COVID-19) and Mycoplasma Pneumonia (MP) are hampered by non-specific symptoms, the lack of rapid responding laboratory measures and the presence of family aggregation. Chest computed tomography (CT) plays a significant role to detect the distribution, density and morphology of lesions caused by either COVID-19 or MP. Objectives: To compare the symptoms, laboratory parameters, and chest CT results of adults with COVID-19 and MP and to assess the use of these findings in the differential diagnosis of these diseases. Patients and Methods: The initial clinical manifestations, laboratory results, and chest CT findings of 45 adult patients with COVID-19 (COVID-19 group) and 55 adult patients with MP (MP group) were reviewed retrospectively. All of the patients were diagnosed in the public hospitals in the epidemic area from 20 January to 28 February 2020. Results: Muscle ache and fatigue were more frequently present in the COVID-19 group (P= 0.009 and 0.029, respectively). Increased procalcitonin levels were more common in the MP group (P = 0.001). The chest CT results indicated that bilateral lung involvement, ground glass opacities, "crazy-paving" patterns, and air bronchogram signs were more common in the COVID-19 group (P < 0.001 for all), respectively. However, single lobe involvement, pulmonary consolidations, lobular central nodules, generalized bronchial wall thickening with luminal stenosis, and bronchial mucus impaction were more common in the MP group (P < 0.001 for all). Receiver operating characteristic analysis of a model established using CT parameters indicated a good or excellent performance in distinguishing COVID-19 from MP. Conclusion: COVID-19 and MP have similar clinical manifestations and laboratory results in early stage. However, the chest CT findings are valuable in the differential diagnosis of these two diseases, particularly in patients from COVID-19 epidemic areas. [ABSTRACT FROM AUTHOR]

New therapies are needed for the treatment of toxoplasmosis, which is a disease caused by the protozoan parasite Toxoplasma gondii. To this end, we previously developed a potent and selective inhibitor (compound 1) of Toxoplasma gondii calcium-dependent protein kinase 1 (TgCDPK1) that possesses antitoxoplasmosis activity in vitro and in vivo. Unfortunately, 1 has potent human ether-a-go-go-related gene (hERG) inhibitory activity, associated with long Q-T syndrome, and consequently presents a cardiotoxicity risk. Here, we describe the identification of an optimized TgCDPK1 inhibitor 32, which does not have a hERG liability and possesses a favorable pharmacokinetic profile in small and large animals. 32 is CNS-penetrant and highly effective in acute and latent mouse models of T. gondii infection, significantly reducing the amount of parasite in the brain, spleen, and peritoneal fluid and reducing brain cysts by >85%. These properties make 32 a promising lead for the development of a new antitoxoplasmosis therapy. [ABSTRACT FROM AUTHOR]