Underwater sensor networks: applications, advances and challenges

This paper examines the main approaches and challenges in the design and implementation of underwater wireless sensor networks. We summarize key applications and the main phenomena related to acoustic propagation, and discuss how they affect the design and operation of communication systems and networking protocols at various layers. We also provide an overview of communications hardware, testbeds and simulation tools available to the research community.     

Multilayer-coated laminar grating with 16% normal-incidence efficiency in the 150-A wavelength region

We characterized a laminar grating with a Mo/Si multilayer coating by using synchrotron radiation and atomic force microscopy. The grating substrate had 2400 grooves/mm, 40-A groove depth, and 2080-A groove width. The microroughness of the grating substrate was 5 A rms. The multilayer coating was optimized to have peak normal-incidence reflectance at a wavelength near 150 A. For an angle of incidence of 10 degrees the peak grating efficiency was 16.3% in the +1 order and 15.0% in the -1 order. The efficiency in the zero order was lower by a factor of 40 owing to the excellent matching of the groove depth and groove width to the wavelength of the incident radiation. By dividing the grating efficiencies by the measured reflectance of the multilayer coating, we obtained inferred groove efficiencies of 34% and 32% in the +1 and -1 orders, respectively.     

Tumor necrosis factor-alpha, interleukin-1 beta, and interleukin-6 concentrations in cerebrospinal fluid predict ventriculoperitoneal shunt infection

OBJECTIVE: To determine the diagnostic value of cerebrospinal fluid tumor necrosis factor (TNF)-alpha, interleukin (IL)-1 beta, and IL-6 released into the cerebrospinal fluid of patients with ventriculoperitoneal shunt infection. DESIGN: Prospective, observational study. SETTING: University teaching hospital. PATIENTS: Sixty-four patients requiring cerebrospinal fluid aspiration for suspected ventriculoperitoneal shunt malfunction. INTERVENTIONS: Cerebrospinal fluid samples were obtained by shunt aspiration at the time of patient presentation. MEASUREMENTS AND MAIN RESULTS: TNF-alpha and IL-1 beta concentrations were measured by enzyme-linked immunosorbent assay, and IL-6 activity by bioassay. The sensitivity, specificity, predictive values, and overall efficiency for each cytokine were determined based on the cerebrospinal fluid culture results. Ten patients had positive cerebrospinal fluid cultures, eight of which yielded Staphylococcus species, and one each Acinetobacter and Pseudomonas. Cerebrospinal fluid TNF-alpha, IL-1 beta, IL-6, protein, and leukocyte concentrations were significantly increased in patients with shunt infection. Cerebrospinal fluid IL-6 activity had the highest diagnostic accuracy of the cytokines evaluated, with sensitivity of 80% and specificity of 98%. CONCLUSIONS: The presence of cerebrospinal fluid inflammatory cytokines strongly suggests ventriculoperitoneal shunt infection. Detection of these cytokines in the cerebrospinal fluid could be used for earlier diagnosis of bacterial infection.     

Re‐orienting the Corporate Entrepreneurial Journey: Exploring the Role of Middle Management

In this article we report research on the implementation of an increased exploitative market orientation in explorative technology‐driven firms, and how the interaction between middle management and the internal context shapes this process. It appears that middle managers play an important role in balancing planned and emergent activities, reconciling market and technological understandings, and negotiating and sanctioning ideas. These roles do not happen automatically. Dominant logics, mindsets and meanings, developed and successful in the past, ‘talk back’. Managerial systems and processes supporting the transition to more and more successful market exploitation are not automatically accepted. Rather, all these and similar changes need to be socially negotiated. In that process, the opportunities and incentives for middle managers to reach beyond their formal job and to engage in the organizational sense‐making process play a key role.     

Advances in network simulation

Network researchers must test Internet protocols under varied conditions to determine whether they are robust and reliable. The paper discusses the Virtual Inter Network Testbed (VINT) project which has enhanced its network simulator and related software to provide several practical innovations that broaden the conditions under which researchers can evaluate network protocols     

Focus-of-attention from local color symmetries

In this paper, a continuous valued measure for local color symmetry is introduced. The new algorithm is an extension of the successful gray value-based symmetry map proposed by Reisfeld et al. The use of color facilitates the detection of focus points (FPs) on objects that are difficult to detect using gray-value contrast only. The detection of FPs is aimed at guiding the attention of an object recognition system; therefore, FPs have to fulfill three major requirements: stability, distinctiveness, and usability. The proposed algorithm is evaluated for these criteria and compared with the gray value-based symmetry measure and two other methods from the literature. Stability is tested against noise, object rotation, and variations of lighting. As a measure for the distinctiveness of FPs, the principal components of FP-centered windows are compared with those of windows at randomly chosen points on a large database of natural images. Finally, usability is evaluated in the context of an object recognition task.     

Combining spatial and colour information for content based image retrieval

Colour is one of the most important features in content based image retrieval. However, colour is rarely used as a feature that codes local spatial information, except for colour texture. This paper presents an approach to represent spatial colour distributions using local principal component analysis (PCA). The representation is based on image windows which are selected by two complementary data driven attentive mechanisms: a symmetry based saliency map and an edge and corner detector. The eigenvectors obtained from local PCA of the selected windows form colour patterns that capture both low and high spatial frequencies, so they are well suited for shape as well as texture representation. Projections of the windows selected from the image database to the local PCs serve as a compact representation for the search database. Queries are formulated by specifying windows within query images. System feedback makes both the search process and the results comprehensible for the user.     

Ternary liquid—liquid equilibria: the van laar equation

The capabilities of the three suffix van Laar equations in predicting the more complex types of ternary liquid—liquid phase diagrams have been examined. While the limitations enforced by thermodynamic consistency on the binary parameters seriously affect the quantitative accuracy with which correlations can be achieved, the van Laar equations are capable of describing qualitatively a variety of complex phenomena. In the system water, n-hexane, phenol, the eruption of a three liquid phase region inside a binodal curve as temperature is decreased is accounted for by the van Laar equation. The similar eruption of a three liquid phase region inside a band in the system glycol, lauryl alcohol, nitroethane is also described. A variety of other types of computed phase diagrams, all of which (save one) have experimental counterparts, are presented. It is also shown that the van Laar equation is capable of quantitatively correct correlation of data for some selected simple systems.     

二羟乙酸~*与胶原的反应及其参与形成稳定的胶原铬交联键的机理

本文研究了二羟乙酸与胶原的反应及其与三价铬及胶原之间交联的机理,为此采用了合成模型化合物,通过高效液相色谱及离子交换液相色谱等方法分离提纯产物,并用核磁共振等方法对产物进行了分析。结果表明二羟乙酸与胶原肽链中的精氨酸的胍基发生了反应,在铬鞣过程中,二羟乙酸与胶原胍基及羧基构成了铬络合物。作者推测,新的稳定交联键是在一般情况下铬不可能与胶原形成交联键的胶原某些区域内构成,这可能是二羟乙酸能提高铬鞣效率的主要原因,因为在每个新的交联键内,只需要一个铬离子,从而为生产实际中有可能减少50%的铬鞣剂用量提供了理论依据。