关于中国放射源管理的建议

1　放射性废物管理方面( 1 )应当建立一个国家级的废放射源管理战略。此战略应包括过去、现在和将来产生的所有放射性废物。此废物管理战略可以由国家指定的委员会来制订。该委员会可以包括来自主要废物的产生单位、废物管理机构和相应的审管部门的代表。此战略应当涵盖技术选择 (处理和处置 )和基础架构 (废物管理机构和基金 )。( 2 )放射性废物管理 ,包括废密封源管理。要求有专门的技术设施和特别训练的人员。为避免基础结构和人力资源重复设置 ,可以考虑单一的废物管理机构。该机构可设有区域性的分支机构 ,也可以设有专门的部门管理来…     

Tensile fracture and failure behavior of technical flax fibers

The apparent tensile strength of technical flax fibers was determined in single‐fiber tests at various clamping lengths (20, 40, and 80 mm) and the outcome was compared with literature data. It was demonstrated that the strength of flax at each clamping length obeyed the two‐parameter Weibull model. The failure mode and sequence were studied in situ (i.e., during loading) by SEM and acoustic emission (AE). The failure sequence (axial splitting of the technical fiber along its elementary constituents, radial cracking of the elementary fibers, multiple fracture of the elementary fibers) concluded reflected the hierarchical build‐up of the flax bast fibers. To the above failure events AE amplitude ranges were assigned. © 2003 Wiley Periodicals, Inc. J Appl Polym Sci 90: 3638–3645, 2003     

Dogs (Canis familiaris) learn their owners via observation in a manipulation task.

Eighty-seven pet dogs (Canis familiaris) were involved in an experiment in which they had to solve a task to obtain a ball. After witnessing a full demonstration by their owner (10 times pushing the handle of the box, which released a ball), most dogs preferred to touch the handle sooner and more frequently in comparison with other parts of the box, and they used the handle to get the ball. In contrast dogs in 3 control groups developed their own respective methods. The lack of emergence of the ball and playing after the demonstration did not affect the learning performance strongly. This suggests that in dogs the outcome of a demonstration plays only a restricted role in the manifestation of social learning. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Midbrain raphe cell firing and hippocampal theta rhythm in urethane-anaesthetized rats

This study aimed to examine the functional coupling between midbrain raphe and the septohippocampal system at the level of neuronal firing. Raphe unit activity and hippocampal EEG were simultaneously recorded in urethane-anaesthetized rats and their relationship was examined in the frequency domain. Subsets of presumably non-serotonergic neurones in both the dorsal and median raphe nuclei fired rhythmically in synchrony with hippocampal theta activity. Theta cells in the median raphe showed higher coherence than those in dorsal raphe and formed a more homogeneous group of cells, according to their firing rates. Since the raphe-septal serotonergic system is known to desynchronize the hippocampal EEG, activation of a subset of nonserotonergic cells during theta in this nucleus indicates a feedback from the limbic circuitry on the ascending raphe control of forebrain activity.     

Melt‐compounded natural rubber nanocomposites with pristine and organophilic layered silicates of natural and synthetic origin

Composites based on natural rubber (NR) and containing organophilic and pristine layered silicates of natural and synthetic origin were produced by melt compounding and sulfur curing. The curing, thermomechanical, and mechanical properties of the mixes, which contained 10 phr (parts per hundred parts of rubber) silicates, were determined. The dispersion of the silicates was studied by X‐ray diffraction (XRD) and transmission electron microscopy (TEM). Organophilic clays accelerated the sulfur curing of NR, which was believed to occur because of a complexation reaction in which the amine groups of the clay intercalants participated. The property improvements caused by the fillers were ranked as follows: organophilic clays > pristine synthetic layered silicate (sodium fluorohectorite) > pristine natural clay (purified sodium bentonite) > precipitated nonlayered silica (used as a reference). This was attributed to partial intercalation of the organophilic clay by NR on the basis of XRD and TEM results and to the high aspect ratio of the fluorohectorite. Apart from intercalation, severe confinement (i.e., the collapse of the interlayer distance) of the organoclays was observed. This peculiar feature was traced to the formation of a zinc coordination complex, which extracted the amine intercalant of the organoclays, thus causing the collapse of the layers. © 2003 Wiley Periodicals, Inc. J Appl Polym Sci 91: 813–819, 2004     

Effects of hygrothermally decomposed polyurethane on the curing and mechanical properties of carbon black‐filled epoxidized natural rubber vulcanizates

Hygrothermally decomposed polyurethane (HD‐PUR) was mixed up to 20 phr in epoxidized natural rubber (with 50 mol % epoxidation; ENR50) recipes, and the curing and mechanical behaviors were studied. Mechanical testing of the ENR50/HD‐PUR vulcanizates determined the tensile, tear, compression‐set, hardness, abrasion, hysteresis, and resilience properties. No significant changes were observed in the tensile properties with the incorporation of HD‐PUR. The ENR50 compounds showed an increase in compression set with increasing HD‐PUR content. Rubbers cured by a semi‐efficient vulcanization system gave the best overall performance. A further improvement in curing and mechanical properties was achieved by the carbon black grade N330 being replaced with a more active grade (N375). © 2002 Wiley Periodicals, Inc. J Appl Polym Sci 84: 2265–2276, 2002     

Toughening of vinylester–urethane hybrid resins through functionalized polymers

Liquid nitrile rubber, hyperbranched polyester, and core/shell rubber particles of various functionality, namely, vinyl, carboxyl, and epoxy, were added up to 20 wt % to a bisphenol‐A‐based vinylester–urethane hybrid (VEUH) resin to improve its toughness. The toughness was characterized by the fracture toughness (K_c) and energy (G_c) determined on compact tensile (CT) specimens at ambient temperature. Toughness improvement in VEUH was mostly achieved when the modifiers reacted with the secondary hydroxyl groups of the bismethacryloxy vinyl ester resin and with the isocyanate of the polyisocyanate compound, instead of participating in the free‐radical crosslinking via styrene copolymerization. Thus, incorporation of carboxyl‐terminated liquid nitrile rubber (CTBN) yielded the highest toughness upgrade with at least a 20 wt % modifier content. It was, however, accompanied by a reduction in both the stiffness and glass transition temperature (T_g) of the VEUH resin. Albeit functionalized (epoxy and vinyl, respectively) hyperbranched polymers were less efficient toughness modifiers than was CTBN, they showed no adverse effect on the stiffness and T_g. Use of core/shell modifiers did not result in toughness improvement. The above changes in the toughness response were traced to the morphology assessed by dynamic mechanical thermal analysis (DMTA) and fractographic inspection of the fracture surface of broken CT specimens. © 2002 Wiley Periodicals, Inc. J Appl Polym Sci 84: 672–680, 2002; DOI 10.1002/app.10392     

Toughness response of vinylester/epoxy‐based thermosets of interpenetrating network structure as a function of the epoxy resin formulation: Effects of the cyclohexylene linkage

Vinylester/epoxy (VE/EP)‐based thermosets of interpenetrating network (IPN) structures were produced by using a VE resin (bismethacryloxy derivative of a bisphenol A–type EP resin) with aliphatic (Al‐EP) and cycloaliphatic (Cal‐EP) EP resins. Curing of the EP resins occurred either with an aliphatic (Al‐Am) or cycloaliphatic diamine compound (Cal‐Am). Dynamic mechanical thermal analysis (DMTA) and atomic force microscopy (AFM) suggested the presence of an interpenetrating network (IPN) in the resulting thermosets. Fracture toughness (K_c) and fracture energy (G_c) were used as the toughness characterization parameters of the linear elastic fracture mechanics. Unexpectedly high K_c and G_c data were found for the systems containing cyclohexylene units in the EP network, such as VE/Al‐EP+Cal‐Am and VE/Cal‐EP+Al‐Am. This was attributed to the beneficial effects of the conformational changes of the cyclohexylene linkages (chair/boat), which were closely analogous to those in some thermoplastic copolyesters. The failure mode of the VE/EP thermoset combinations was studied in scanning electron microscopy (SEM) and discussed. © 2003 Wiley Periodicals, Inc. J Appl Polym Sci 88: 2124–2131, 2003     

On the in‐situ polymerization of cyclic butylene terephthalate oligomers: DSC and rheological studies

The thermal and rheological behaviors of cyclic butylene terephthalate (CBT) were studied with differential scanning calorimetry (DSC) and plate–plate rheometry, respectively. DSC scans were taken at different heating rates. The related first‐heat thermograms indicated crystallization and melting of the resulting poly (butylene terephthalate) (PBT) only at very low heating rate (0.5°C/min). As the crystallization and melting enthalpies were closely matched, one could conclude that the polymerization is essentially athermic. The polymerization was accompanied by a steep increase of the melt viscosity in isothermal rheological tests performed in the temperature range T = 145–210°C. Changes in the viscoelasticity of the polymerizing CBT and crystallizing PBT could be best followed by considering the changes in the phase angle. Viscosity increased with the conversion exponentially in the first approximation. POLYM. ENG. SCI., 46:743–750, 2006. © 2006 Society of Plastics Engineers     

A Comparative Study of the Use of Visual Communicative Signals in Interactions Between Dogs (Canis familiaris) and Humans and Cats (Felis catus) and Humans.

Dogs' (Canis familiaris) and cats' (Felis catus) interspecific communicative behavior toward humans was investigated. In Experiment 1, the ability of dogs and cats to use human pointing gestures in an object-choice task was compared using 4 types of pointing cues differing in distance between the signaled object and the end of the fingertip and in visibility duration of the given signal. Using these gestures, both dogs and cats were able to find the hidden food; there was no significant difference in their performance. In Experiment 2, the hidden food was made inaccessible to the subjects to determine whether they could indicate the place of the hidden food to a naive owner. Cats lacked some components of attention-getting behavior compared with dogs. The results suggest that individual familiarization with pointing gestures ensures high-level performance in the presence of such gestures; however, species-specific differences could cause differences in signaling toward the human. (PsycINFO Database Record (c) 2010 APA, all rights reserved)