Competitive adsorption of heavy metal ions (Pb2+, Cu2+, and Ni2+) onto date seed biochar: batch and fixed bed experiments

In a multicomponent systems, the adsorption of Pb²⁺, Cu²⁺, and Ni²⁺ by date seed biochar exhibited competitive behavior. Compared to single component systems, the adsorption capacities of each ion were reduced by 48–75% in both batch and column experiments. Surface complexation with carboxyl and hydroxyl functional groups played a major role in the removal mechanism. Ion exchange mechanism accounted for 37–40% of the total adsorption compared to 57–72% in single component systems. Modified Langmuir isotherm best described the systems. Adsorption capacities and selectivity follow the order: Pb²⁺> Cu²⁺> Ni²⁺. Multi-stage sequences system is recommended to avoid premature exhaustion of biochar.     

Relaxor behavior of (1 − x)BaTiO3–x(Bi3/4Na1/4)(Mg1/4Ti3/4)O3 (0.2 ≤ x ≤ 0.9) ferroelectric ceramic

The (1 − x)BaTiO₃–x(Bi_3/4Na_1/4)(Mg_1/4Ti_3/4)O₃ (0.2 ≤ x ≤ 0.9) ceramics were prepared by conventional solid-state reaction route. Their dielectric properties were found to follow a modified Curie–Weiss law and an empirical Lorenz-type relation in respective temperature regions. Their dielectric relaxation times fit well with the Vogel–Fulcher relation for x = 0.2, 0.3, and 0.4. For x = 0.5, 0.6, 0.7, and 0.8, however, the fitting curves of Vogel–Fulcher relation showed certain deviation from the experimental data. Based on the theoretical treatment of Landau–Ginsburg–Devonshire theory, an approximate treatment of the E-field dependence of the permittivity was adopted and found to describe well the field dependence of the permittivity for x = 0.3 at temperatures equal to and below T _m (temperature of maximum dielectric permittivity). A combined Langevin-type expression used in the present work appears to give a good account for the field dependence of the permittivity, assuming polar regions are of a statistical cluster size. For polar clusters of linear dimension L ~ 4–8 nm for instance, the fitted values of polarization are in the range of P ~ 6.2–9.8 μC/cm².     

Plasmonic intravascular photoacoustic imaging for detection of macrophages in atherosclerotic plaques

To detect macrophages in atherosclerotic plaques, plasmonic gold nanoparticles are introduced as a contrast agent for intravascular photoacoustic imaging. The phantom and ex vivo tissue studies show that the individual spherical nanoparticles, resonant at 530 nm wavelength, produce a weak photoacoustic signal at 680 nm wavelength while photoacoustic signal from nanoparticles internalized by macrophages is very strong due to the plasmon resonance coupling effect. These results suggest that intravascular photoacoustic imaging can assess the macrophage-mediated aggregation of nanoparticles and therefore identify the presence and the location of nanoparticles associated with macrophage-rich atherosclerotic plaques.     

Coordinated buckling of thick multi-walled carbon nanotubes under uniaxial compression

Using a generalized quasi-continuum method, we characterize the post-buckling morphologies and energetics of thick multi-walled carbon nanotubes (MWCNTs) under uniaxial compression. Our simulations identify for the first time evolving post-buckling morphologies, ranging from asymmetric periodic rippling to a helical diamond pattern. We attribute the evolving morphologies to the coordinated buckling of the constituent shells. The post-buckling morphologies result in significantly reduced effective moduli that are strongly dependent on the aspect ratio. Our simulation results provide fundamental principles to guide the future design of high-performance, MWCNT-based nanodevices.      

A MALDI-TOF MS study of oligomeric poly(m-phenyleneisophthalamide)

MALDI-TOF MS was used to study the end-group distribution of a series of poly(m-phenyleneisophthalamide) oligomers which were synthesized using various mole percent ratios of diamine to diacid chloride (90:10, 80:20, 70:30, 60:40, 50:50, 40:60, 30:70, 20:80, and 10:90) to clarify results obtained in previous work published in this journal. Oligomers synthesized with excess diamine or excess diacid chloride were found to contain abundances of amine or carboxylate end groups, respectively, as expected. Oligomers synthesized with equal molar ratios of reactants produced cyclic species which were also found in a previous publication as an oligomer in commercially produced, high molecular mass Nomex.     

High-throughput solution-based medicinal library screening against human serum albumin

High-throughput screening of combinatorial libraries has evolved from studying large diverse libraries to analyzing small, structurally similar, focused libraries. This paradigm shift has generated a need for rapid screening technologies to screen both diverse and focused libraries in a simple, efficient, and inexpensive manner. We have proactively addressed these needs by developing a high-throughput, solution-based method combining size exclusion (SEC), two-dimensional liquid chromatography (2-D LC), and mass spectrometry (MS) for determining the relative binding of drug candidates in small, focused medicinal libraries against human serum albumin (HSA). Two types of libraries were used to evaluate the performance of the system. The first consisted of five diverse ligands with a wide range of hydrophobicities and whose association constants to HSA cover 3 orders of magnitude. A beta-lactam library composed of structurally similar compounds was used to further confirm the validity of the methodology. The ability to distinguish site-specific interactions of drugs competing for individual domains of the HSA receptor is also demonstrated. Comparison of chromatographic profiles of the library components before and after incubation with the receptor using multiple reaction monitoring allowed a ranking of the ligands according to their relative binding affinities. The observed rankings correlate closely with literature values of the association constants between the respective ligands and HSA. This simple, rugged methodology can screen a wide spectrum of chemical entities from combinatorial mixtures in less than 6 min.     

Supercritical fluid extraction to determine the oil content in copra and extracted meal

Supercritical fluid extraction (SFE) was used as a primary method to determine the oil content of copra and its meal. Determination of the oil content of copra takes 9 h, and for meal 6 h are necessary with Soxhlet extraction, whereas SFE determined oil contents in about 10 min. The extremely high oil content of copra makes grinding difficult, as the sample becomes very gummy and it is difficult to remove the entire sample from the grinder. Adding diatomaceous earth to the sample before grinding eliminated the difficulties of cleaning the grinder and also enabled very fast SFE extractions. The variances for Soxhlet and SFE were not significantly different from each other (P>0.10) in both copra and meal oil contents. The 95% confidence interval around the mean differences (SFE-Soxhlet) was (−0.35, 0.90) and (0.08, 0.26) and for copra and meal, respectively. Although the SFE meal oil content (9.81%) was significantly higher than the Soxhlet meal oil content (9.64%), the size of the average difference (0.17%) was relatively small. This small difference was considered acceptable owing to the ability to use SFE in real-time process control. Therefore, SFE can be used to determine the oil content in copra and its meal in less than 10 min.     

Impacts of the Sustainable Forestry Initiative Landscape Level Measures on Hydrological Processes

The effects on hydrological processes of the application of the landscape level measures included in the sustainable forestry initiative (SFI) program were analyzed through simulation. A landscape scenario where limitation of harvesting units size, imposition of a green-up interval, and establishment of streamside management zones (SMZ) were simulated was compared with a reference scenario where no SFI rules were followed. An intensively managed forested landscape located in East Texas, USA, was used as the study area. The HARVEST landscape model was used to simulate landscape pattern and a modified version of the APEX model was used to simulate hydrological processes. Water and sediment yields were generally small within the observation period and most of the runoff and erosion observed occurred during intense storm events. Water and sediment yield at the subarea level and water yield at the watershed level were similar in both scenarios. However, sediment yield at the watershed level was higher in the non-SFI scenario. The differences were due to the reduction in channel erosion resulting from the presence of SMZs. The effect of buffer zones in terms of sediment deposition was not different between scenarios, which can be attributed to the level slopes of the study area. Landscape measures of the SFI program, namely buffer zones, seem important in reducing channel degradation, particularly during major storm events, in intensively managed forest landscapes in East Texas.     

Molecular weights of polyethylene and polypropylene by vapor pressure osmometry at elevated temperatures

The Wescan Model 232-A VPO was modified with a 12 volt regulated power supply for supplying bridge current and with thermocouples to allow for direct digital readout of the syringe box and measuring chamber temperatures. The modified instrument was used to measure M _n of standard (NBS) polyethylenes. Agreement with NBS values was good (within 10%) for M _n < 3 × 10⁴ and fair (within 20%) for M _n = 1 × 10⁵. Results on M _n of commercial polypropylenes are also reported.     

Synthesis and characterization of poly(methyl methacrylate) star polymers

Star-branched poly(methyl methacrylate)s (PMMA) were synthesized by linking ‘living’ arms (produced by anionic polymerzation) with ethylene glycol dimethacrylate. Stars having arm molecular weights of 10000 and 40000 and between 4.9 and 18.7 branches were produced. The polymers were characterized using light scattering, size exclusion chromatography, and viscometry. It was found that well-defined PMMA stars were obtained only at the higher (40000) arm molecular weight. The stars prepared using the lower molecular weight (c. 10000) arms contained very high molecular weight gel components.