Epitaxial crystallization of olefin block copolymers (OBCs) on uniaxially oriented isotactic polypropylene and high-density polyethylene films

The epitaxial crystallization behavior of olefin block copolymers (OBCs) on uniaxially oriented isotactic polypropylene (iPP) and high-density polyethylene (HDPE) films has been investigated by transmission electron microscopy (TEM). The crystallizable blocks of the OBCs under investigation were epitaxially nucleated by both iPP and HDPE substrates and epitaxial growth of OBC lamellae was observed. Epitaxial crystallization of the OBCs has been found for slow and fast cooling conditions from the melt which pointed to the strong interaction between the polyolefin substrates and the OBCs. However, the epitaxial morphology of the OBCs strongly depends on their octene concentration difference (Δ_C8) between crystallizable and non-crystallizable blocks, which probably is related to the OBC segregation strength in the melt. With high Δ_C8 the development of epitaxial crystallization of the OBC was restricted within isolated crystalline domains surrounded by the amorphous phase. In contrast, with low Δ_C8 the oriented lamellae of the OBC were distributed homogeneously on iPP but formed separated crystalline domains on HDPE, which has a stronger nucleation capability than iPP on the crystalline OBC blocks because of its similar molecular architecture. Our study points to epitaxy as another reason for the strong interaction between OBC and polyolefins which causes the advanced compatibilization behavior of OBCs when compared with conventional random copolymers.     

Redundancy resolution of the human arm and an upper limb exoskeleton

The human arm has 7 degrees of freedom (DOF) while only 6 DOF are required to position the wrist and orient the palm. Thus, the inverse kinematics of an human arm has a nonunique solution. Resolving this redundancy becomes critical as the human interacts with a wearable robot and the inverse kinematics solution of these two coupled systems must be identical to guarantee an seamless integration. The redundancy of the arm can be formulated by defining the swivel angle, the rotation angle of the plane defined by the upper and lower arm around a virtual axis that connects the shoulder and wrist joints. Analyzing reaching tasks recorded with a motion capture system indicates that the swivel angle is selected such that when the elbow joint is flexed, the palm points to the head. Based on these experimental results, a new criterion is formed to resolve the human arm redundancy. This criterion was implemented into the control algorithm of an upper limb 7-DOF wearable robot. Experimental results indicate that by using the proposed redundancy resolution criterion, the error between the predicted and the actual swivel angle adopted by the motor control system is less then 5°.     

LaAlO<Subscript>3</Subscript>/SrTiO<Subscript>3</Subscript> Epitaxial Heterostructures by Atomic Layer Deposition

Thin films of LaAlO₃ were deposited on TiO₂-terminated (100) SrTiO₃ crystals by atomic layer deposition (ALD), using tris(iso-propylcyclopentadienyl)lanthanum and trimethyl aluminum precursors. Water was used as the oxidizer. The film composition was shown to be controlled by the ratio of La/Al precursor pulses during ALD, with near-stoichiometric LaAlO₃ resulting at precursor pulse ratios of 4/1 to 5/1. Films near the stoichiometric LaAlO₃ composition were shown to crystallize on subsequent annealing to form epitaxial LaAlO₃/SrTiO₃ heterostructures. Electrical characterization of these structures was done by two-terminal direct-current (DC) current–voltage scans at room temperature and under high-vacuum conditions. The results show electrical conductivity for the ALD-deposited epitaxial LaAlO₃/SrTiO₃ heterostructures, which turns on for thickness above four unit cells for the LaAlO₃ film.     

Annealing-Induced Morphological Changes in Nanocrystalline Quantum Dots and Their Impact on Charge Transport Properties

The effects of thermal annealing on the morphological and photoconductive properties of cadmium selenide quantum dots coated with zinc sulfide are studied. The results of transmission electron microscopy with in situ annealing show a number of events taking place simultaneously, including aggregation of dots, changes in the size and shape distribution, and reduction in interdot separation. Transient absorption results indicate that there is a small redshift of the spectrum. There is a shortening of the absorption decay lifetimes due to annealing. Higher photocurrents are measured in the annealed compared with unannealed dots at room temperature.     

Large shift in source of fine sediment in the upper Mississippi river

Although sediment is a natural constituent of rivers, excess loading to rivers and streams is a leading cause of impairment and biodiversity loss. Remedial actions require identification of the sources and mechanisms of sediment supply. This task is complicated by the scale and complexity of large watersheds as well as changes in climate and land use that alter the drivers of sediment supply. Previous studies in Lake Pepin, a natural lake on the Mississippi River, indicate that sediment supply to the lake has increased 10-fold over the past 150 years. Herein we combine geochemical fingerprinting and a suite of geomorphic change detection techniques with a sediment mass balance for a tributary watershed to demonstrate that, although the sediment loading remains very large, the dominant source of sediment has shifted from agricultural soil erosion to accelerated erosion of stream banks and bluffs, driven by increased river discharge. Such hydrologic amplification of natural erosion processes calls for a new approach to watershed sediment modeling that explicitly accounts for channel and floodplain dynamics that amplify or dampen landscape processes. Further, this finding illustrates a new challenge in remediating nonpoint sediment pollution and indicates that management efforts must expand from soil erosion to factors contributing to increased water runoff.     

Attachment and biofilm formation by Escherichia coli O157:H7 at different temperatures, on various food-contact surfaces encountered in beef processing

Escherichia coli O157:H7 attached to beef-contact surfaces found in beef fabrication facilities may serve as a source of cross-contamination. This study evaluated E. coli O157:H7 attachment, survival and growth on food-contact surfaces under simulated beef processing conditions. Stainless steel and high-density polyethylene surfaces (2 × 5 cm) were individually suspended into each of three substrates inoculated (6 log CFU/ml or g) with E. coli O157:H7 (rifampicin-resistant, six-strain composite) and then incubated (168 h) statically at 4 or 15 °C. The three tested soiling substrates included sterile tryptic soy broth (TSB), unsterilized beef fat-lean tissue (1:1 [wt/wt]) homogenate (10% [wt/wt] with sterile distilled water) and unsterilized ground beef. Initial adherence/attachment of E. coli O157:H7 (0.9 to 2.9 log CFU/cm²) on stainless steel and high-density polyethylene was not affected by the type of food-contact surface but was greater (p < 0.05) through ground beef. Adherent and suspended E. coli O157:H7 counts increased during storage at 15 °C (168 h) by 2.2 to 5.4 log CFU/cm² and 1.0 to 2.8 log CFU/ml or g, respectively. At 4 °C (168 h), although pathogen levels decreased slightly in the substrates, numbers of adherent cells remained constant on coupons in ground beef (2.4 to 2.5 log CFU/cm²) and increased on coupons in TSB and fat-lean tissue homogenate by 0.9 to 1.0 and 1.7 to 2.0 log CFU/cm², respectively, suggesting further cell attachment. The results of this study indicate that E. coli O157:H7 attachment to beef-contact surfaces was influenced by the type of soiling substrate and temperature. Notably, attachment occurred not only at a temperature representative of beef fabrication areas during non-production hours (15 °C), but also during cold storage (4 °C) temperatures, thus, rendering the design of more effective sanitation programs necessary.     

Effects of fine grinding of millfeeds on the quality attributes of reconstituted whole-wheat flour and its raw noodle products

Effects of millfeed particle size on the quality of whole-wheat flour (WWF) and raw noodles were investigated. Four ranges of particle size distribution of millfeeds from hard red spring (median diameter: 307, 260, 225, and 178 μm) and hard red winter (median diameter: 319, 274, 235, and 185 μm) were obtained by fine grinding. For both wheat classes, the CIE L* values of WWF decreased and a* and b* values increased with the reduction of millfeed particle sizes. WWF with finer millfeeds exhibited higher PPO activity than that with coarser millfeeds. RVA analysis showed that peak viscosity, trough, and final viscosity of WWF significantly decreased as the particle size of millfeeds reduced, while breakdown and setback values revealed no obvious trend. Reducing the particles of millfeeds not only significantly increased the Farinograph stability time of WWF dough, but also improved the whole-wheat noodle (WWN) brightness (L*) at both 0 and 24 h. Texture profile analysis of cooked noodle indicated that hardness, springiness, cohesiveness and resilience values all significantly increased as the particle sizes of millfeeds were decreased. These results suggest that reduction of millfeed particle sizes before reconstituting WWF could provide beneficial effect on the quality improvement of WWN.