Highly Stretchable Polymers: Mechanical Properties Improvement by Balancing Intra‐ and Intermolecular Interactions

The mechanical properties of polymers are highly dependent on the mobility of the underlying chains. Changes in polymer architecture can affect inter‐ and intramolecular interactions, resulting in different chain dynamics. Herein, an enhancement in the mechanical properties of poly(butylmethacrylate) is induced by folding the polymer chains through covalent intramolecular crosslinking (CL). Intramolecular CL causes an increase in intramolecular interactions and inhibition of intermolecular interactions. In both the glassy and rubbery states, this molecular rearrangement increases material stiffness. In the glassy state, this molecular rearrangement also leads to reduced failure strain, but surprisingly, in the rubbery state, the large strain elasticity is actually increased. An intermediate intramolecular CL degree, where there is a balance between intra‐ and intermolecular interactions, shows optimal mechanical properties. Molecular dynamics simulations are used to confirm and provide molecular mechanisms to explain the experimental results.     

Scour depths at sites selected for spawning by brown trout (Salmo trutta) along a longitudinal gradient of a North American mountain river

In the Intermountain West, USA, fry of fall‐spawning brown trout (Salmo trutta) are susceptible to scour‐related mortality because they are still in the gravel during spring snowmelt run‐off events. The goal of our research was to understand patterns of gravel scour on the Logan River, Utah, in relation to brown trout spawning and whether mobility of spawning gravels could explain the absence of brown trout from higher elevations. We collected data to characterize local entrainment potential at spawning gravels longitudinally on the Logan River during 2009 and 2010 spring flood events. We used scour chains to measure scour depth at spawning locations, and we also examined the position of redds in channel cross sections in relation to the centre line. The flood magnitude in both years approximated the 2‐year flood magnitude, but the flood in 2009 was much longer in duration. Scour at 27% of scour chain locations exceeded the estimated median upper limit of developing fry in 2009, whereas scour at 0% of locations exceeded this depth in 2010. Brown trout spawned in locations with similar entrainment potential at both mid and high elevations, which contributed to a lack of trend in scour depth with elevation. In addition, the majority of areas chosen for spawning were channel margins. The relationship between local entrainment potential at spawning gravels and scour depth was similar for the mid‐elevation canyon zone with medium brown trout density and the high‐elevation noncanyon zone with low brown trout density. In a low‐elevation backwater zone containing high densities of brown trout, scour was high despite low levels of entrainment potential. Overall, findings suggest that spawning gravel scour is not limiting brown trout abundance at high elevations in this system given shallow scour depths overall and a general lack of increase in scour depth with increasing elevation/distance upstream.     

Macroscale Biomolecular Electronics and Ionics

The conduction of ions and electrons over multiple length scales is central to the processes that drive the biological world. The multidisciplinary attempts to elucidate the physics and chemistry of electron, proton, and ion transfer in biological charge transfer have focused primarily on the nano‐ and microscales. However, recently significant progress has been made on biomolecular materials that can support ion and electron currents over millimeters if not centimeters. Likewise, similar transport phenomena in organic semiconductors and ionics have led to new innovations in a wide variety of applications from energy generation and storage to displays and bioelectronics. Here, the underlying principles of conduction on the macroscale in biomolecular materials are discussed, highlighting recent examples, and particularly the establishment of accurate structure–property relationships to guide rationale material and device design. The technological viability of biomolecular electronics and ionics is also discussed.     

基于深度迁移学习的网络入侵检测

为解决网络入侵检测问题,提高检测准确率和降低误报率,提出一种基于深度迁移学习的网络入侵检测方法,该方法使用非监督学习的深度自编码器来进行迁移学习,实现网络的入侵检测。首先对深度迁移学习问题进行建模,然后对深度模型进行迁移学习。迁移学习框架由嵌入层和标签层实现编/解码,编码和解码权重由源域和目标域共享,用于知识的迁移。嵌入层中,通过最小化域之间的嵌入实例的KL散度来强制源域和目标域数据的分布相似;在标签编码层中,使用softmax回归模型对源域的标签信息进行编码分类。实验结果表明,该方法能够实现网络入侵检测,且性能优于其他入侵检测方法。     

完井方式对适度出砂井产能的影响研究

为了完善近几年提出的海上稠油油藏开采新模式中的部分技术——以钻井压裂、适度出砂、电潜螺杆泵为主的钻采工艺配套技术体系,根据不同完井方式（包括裸眼完井、射孔完井、筛管完井等）下钻井压裂井的表皮系数模型和产能模型,研究了不同完井方式下不同技术参数对钻井压裂适度出砂井的产能影响,结果表明,这些参数都不同程度地影响着井筒周围的出砂带物性,进而影响油井产能;在用适度出砂方式开采时,要严格评价完井方式及其技术参数对出砂带物性和产能的影响。     

Phosphorous limitation in an arctic river biofilm—A whole ecosystem experiment

A fourth-order arctic river was experimentally enriched with phosphate (7.7 ± 7.0 μ g 1⁻¹) to determine the effect of such a loading (equivalent to a community of 10,000 people) upon the trophically important biofilm. The effect upon a light-grown biofilm (an autotrophic/heterotrophic assemblage) and a dark-grown biofilm (predominantly heterotrophic assemblage) was determined after 28 days of colonization. Seven attributes of the biofilms were monitored, 2 autotrophic indices, chlorophyll , [¹⁴C]HCO₃ incorporation into lipids and 5 heterotrophic indices; [¹⁴C]acetate incorporation into lipids, metabolic heat output, turn-over times of microbially labile glucose and glutamate and mineralization of microbially recalcitrant ring-labelled [¹⁴C]hydroxybenzoic acid. The findings showed that the addition of phosphorus resulted in a substantial stimulation of both autotrophic and heterotrophic processes suggesting that arctic rivers of this type would be liable to cultural eutrophication.     

Coherent sea-level fluctuations along the global continental slope

Signals in sea-level or, more properly, sub-surface pressure (SSP; sea-level corrected for the inverse barometer effect) are expected to propagate rapidly along the continental slope due to the effect of sloping topography on wave modes, resulting in strongly correlated SSP over long-distances. Observations of such correlations around the Arctic and Antarctic are briefly reviewed, and then extended using satellite altimetry to the rest of the global continental slope. It is shown that such long-distance correlations are common, especially in extra-tropical regions. Simple correlations from altimetry cannot, however, establish the wave speed, or whether waves are responsible for the correlations as opposed to large-scale coherence in the forcing. A case study around South America is used to highlight some of the complications, and is found to strengthen the case for the importance of wave modes in such long-distance SSP coherence, although more detailed in situ data are required to resolve the cause of the correlations.     

Near-infrared (NIR) Raman spectroscopy of Precambrian carbonate stromatolites with post-depositional organic inclusions

Raman spectroscopy has promising potential for future Mars missions as a non-contact detection technique for characterizing organic material and mineralogy. Such a capability will be useful for selecting samples for detailed analysis on a rover and for selecting samples for return to Earth. Stromatolites are important evidence for the earliest life on Earth and are promising targets for Mars investigations. Although constructed by microorganisms, stromatolites are organo-sedimentary structures that can be large enough to be discovered and investigated by a Mars rover. In this paper, we report the Raman spectroscopic investigations of the carbonate mineralogy and organic layering in a Precambrian (~1.5 Gyr old) stromatolite from the Crystal Spring Formation of Southern California. Ultraviolet (UV: 266 nm), visible (514 nm, 633 nm), and near-infrared (NIR: 785 nm, 1064 nm) Raman spectra are presented. We conclude that 1064 nm excitation is the optimal excitation wavelength for avoiding intrinsic fluorescence and detecting organic carbon within the carbonate matrix. Our results confirm that NIR Raman spectroscopy has important applications for future Mars missions.     

Maternal mood, video-mediated cognitions, and daily stress during home-based, family interactions.

This article presents an in vivo investigation of maternal negative mood, maternal video-mediated cognitions, and daily stressors in families with young children. Specifically, it was hypothesized that greater levels of maternal depressed, anxious, and hostile mood states immediately prior to a daily, reportedly routine, stressful parent–child interaction would be significantly associated with higher percentages of dysfunctional and lower percentages of functional cognitions. Forty-five mothers of 2- to 5-year-old children participated in this study by rating their mood before being videotaped in a daily routine with their child they reported as recurrent and stressful (e.g., mealtime). Using video-mediated recall (VMR) methodology, mothers were instructed to recall their cognitions upon immediate video review. Results indicated that greater levels of negative mood were associated with a greater percentage of dysfunctional cognitions and a smaller percentage of functional cognitions. Levels of maternal depressed mood were significantly and independently associated with greater rates of dysfunctional and lower rates of functional cognitions. Negative mood states were not consistently associated with the amount of maternal self-reported general irrationality, pointing to the utility of the VMR to elicit maternal cognitions specific to the observed interaction, which may have more implications for clinical intervention than more general irrationality measures. Evaluating maternal mood and using video-mediated maternal cognitions regarding daily family stressors can precipitate clinical interventions meant to reduce family-related stress and potentially improve maternal and child mental health outcomes. (PsycINFO Database Record (c) 2010 APA, all rights reserved)