Is the Donnan effect sufficient to explain swelling in brain tissue slices?

Brain tissue swelling is a dangerous consequence of traumatic injury and is associated with raised intracranial pressure and restricted blood flow. We consider the mechanical effects that drive swelling of brain tissue slices in an ionic solution bath, motivated by recent experimental results that showed that the volume change of tissue slices depends on the ionic concentration of the bathing solution. This result was attributed to the presence of large charged molecules that induce ion concentration gradients to ensure electroneutrality (the Donnan effect), leading to osmotic pressures and water accumulation. We use a mathematical triphasic model for soft tissue to characterize the underlying processes that could lead to the volume changes observed experimentally. We suggest that swelling is caused by an osmotic pressure increase driven by both non-permeating solutes released by necrotic cells, in addition to the Donnan effect. Both effects are necessary to explain the dependence of the tissue slice volume on the ionic bath concentration that was observed experimentally.     

Is color patchy?

In many natural scenes, shadows and shading, which are primarily luminance-defined features, proliferate. Hence one might expect that the chromatic variations of natural scenes, which more faithfully represent the layout of object surfaces, will contain relatively fewer and larger uniform regions than the luminance variations, i.e., will be more "patchy." This idea was tested using images of natural scenes that were decomposed into chromatic and luminance layers modeled as the responses of the red-green, blue-yellow, and luminance channels of the human visual system. Patchiness was defined as the portion of pixels falling within a +/- threshold in the bandpass-filtered image, averaged across multiple filter scales. The red-green layers were found to be the most patchy, followed by the blue-yellow layers, with the luminance layers the least patchy. The correlation between image-layer patchiness and the slope of the Fourier amplitude spectrum was small and negative for all layers, the maximum value being for red-green (-0.48). We conclude that the chromatic layers of natural scenes contain more uniform areas than the luminance layers and that this is unpredicted by the slope of the Fourier amplitude spectrum.     

Is graphene aromatic?

We analyze the chemical bonding in graphene using a fragmental approach, the adaptive natural density partitioning method, electron sharing indices, and nucleus-independent chemical shift indices. We prove that graphene is aromatic, but its aromaticity is different from the aromaticity in benzene, coronene, or circumcoronene. Aromaticity in graphene is local with two π-electrons delocalized over every hexagon ring. We believe that the chemical bonding picture developed for graphene will be helpful for understanding chemical bonding in defects such as point defects, single-, double-, and multiple vacancies, carbon adatoms, foreign adatoms, substitutional impurities, and new materials that are derivatives of graphene.      

Pruritus: Is there a grain of salty truth?

Hemodialysis patients characteristically suffer from a range of unpleasant symptoms. Uremic pruritus effects close to half of the chronic kidney disease population, reducing quality of life and associated with increased mortality. Its pathophysiology though is poorly understood; currently deployed therapeutic approaches are ineffective. Excessive levels of skin and soft tissue sodium accumulate in dialysis patients, producing a range of biological consequences, including inflammation. We report an index case of a hemodialysis patient with debilitating pruritus and extreme levels of tissue sodium, measured with Sodium-23 magnetic resonance imaging. Both the tissue sodium loading and pruritus responded fully to initiation of expanded hemodialysis therapy with a recently introduced medium cutoff dialysis membrane-based dialyzer.     

Injuries and Safe Communities Accreditation: Is there a link?

Safe Communities (SC) is a global movement that brings together community stakeholders to collaboratively address injury concerns. SC accreditation is a formal process through which communities are recognized for strengthening local injury prevention capacity. Six million Americans live in 25 SC sites, but no research has been done to understand the model’s potential impact on this population. This study explored the temporal relationship between SC accreditation and injury trends in three SC sites from the state of Illinois—Arlington Heights, Itasca, and New Lenox. Hospitalization data, including patient demographics, exposure information, injury outcomes, and economic variables, were obtained from a statewide hospital discharge database for a 12-year period (1999–2011). Joinpoint regression models were fitted to identify any periods of significant change, examine the direction of the injury trend, and to estimate monthly percent changes in injury counts and rates. Poisson random-intercept regression measured the average total change since the official SC accreditation for the three communities combined and compared them to three matched control sites. In joinpoint regression, one of the SC sites showed a 10-year increase in hospitalization cases and rates followed by a two-year decline, and the trend reversal occurred while the community was pursuing the SC accreditation. Injury hospitalizations decreased after accreditation compared to the pre-accreditation period when SC sites were compared to their control counterparts using Poisson modeling. Our findings suggest that the SC model may be a promising approach to reduce injuries. Further research is warranted to replicate these findings in other communities.     

Fatigue in Rotating Equipment: Is it HCF or LCF?

This article discusses practical differences between high-cycle fatigue and low-cycle fatigue at relatively lower temperatures in rotating equipment and the equipment attached to it. Methods to identify the failure mode are discussed so proper prevention measures can be put in place to prevent future occurrences. Examples of typical components are provided to show the methods in action.     

Circular economy: Is there anything new in this concept?

Clean Technologies and Environmental Policy -     

Is the water rising?

When a quantity is changing slowly it is difficult to know whetherit will continue to monotonically increase. This situation mayraise questions as to when there is a problem and what shouldbe done. Is the average level of the world's oceans rising?There is some evidence to support this contention. Is this situationa matter of concern that requires action, and what should thataction be? These are vexing questions. Ionising radiation certainly     

Is the Universe homogeneous?

The standard model of cosmology is based on the existence of homogeneous surfaces as the background arena for structure formation. Homogeneity underpins both general relativistic and modified gravity models and is central to the way in which we interpret observations of the cosmic microwave background (CMB) and the galaxy distribution. However, homogeneity cannot be directly observed in the galaxy distribution or CMB, even with perfect observations, since we observe on the past light cone and not on spatial surfaces. We can directly observe and test for isotropy, but to link this to homogeneity we need to assume the Copernican principle (CP). First, we discuss the link between isotropic observations on the past light cone and isotropic space-time geometry: what observations do we need to be isotropic in order to deduce space-time isotropy? Second, we discuss what we can say with the Copernican assumption. The most powerful result is based on the CMB: the vanishing of the dipole, quadrupole and octupole of the CMB is sufficient to impose homogeneity. Real observations lead to near-isotropy on large scales--does this lead to near-homogeneity? There are important partial results, and we discuss why this remains a difficult open question. Thus, we are currently unable to prove homogeneity of the Universe on large scales, even with the CP. However, we can use observations of the cosmic microwave background, galaxies and clusters to test homogeneity itself.     

Microstructurally inhomogeneous composites: Is a homogeneous reinforcement distribution optimal?

Since the 1960s, it has been a common practice worldwide to pursue a homogeneous distribution of reinforcements within a matrix material, discontinuous metal matrix composites (DMMCs) in particular. Taking an overview of the worldwide activities in DMMC research, despite many favourable attributes such as improved specific strength, stiffness and superior wear resistance, DMMCs with a homogeneous microstructure tend to exhibit a very low room temperature damage tolerance even with a highly ductile matrix material such as aluminium. In this review, a range of uniquely multi-scale hierarchical structures have been successfully designed and fabricated by tailoring reinforcement distribution for DMMCs in order to obtain superior performance. A variety of specific microstructures that were developed in Al, Mg, Cu, Fe, Co and TiAl matrices indicate that there must be adequate plastic regions among the reinforcements to blunt or deflect cracks if one wants to toughen DMMCs. Following this path, aided by theoretical analyses, the most recent success is the design and fabrication of a network distribution of in situ reinforcing TiB whiskers (TiBw) in titanium matrix composites (TMCs), where a tailored three-dimensional (3D) quasi-continuous network microstructure displays significant improvements in mechanical properties. This resolves the brittleness surrounding TMCs fabricated by powder metallurgy. It is the large reinforcement-lean regions that remarkably improve the composite’s ductility by bearing strain, blunting the crack and decreasing the crack-propagation rate. The fracture, strengthening and toughening mechanisms are comprehensively elucidated in order to further understand the advantages of such an inhomogeneous microstructure, and to justify the development of novel techniques to produce such inhomogeneous microstructures. This approach opens up a new horizon of research and applications of DMMCs and can be easily extended to general multi-phase composites with enhanced physical and mechanical properties.     

Is motion processing unitary?

Motion discrimination space is conventionally categorized into motion detection, speed discrimination, and direction discrimination tasks. But an ideal observer uses a unitary motion mechanism that is affected only by the noise level and the difference in speed (or displacement) between two stimuli. We tested whether human performance in the various motion tasks showed the working of a unitary mechanism or the combined outputs of more than one mechanism. We examined the whole motion discrimination space, using random dots that underwent a sudden jump or displacement. The discriminability was measured as a function of the standard and comparison displacements. Both the ideal observer model and a nonideal observer model that contains additive internal noise predict a planar response surface. When the dot motion was noiseless, the planar surface fitted well except for much higher than expected sensitivity for motion detection. This is consistent with a purely temporal mechanism that uses flicker or a purely spatial mechanism that uses the length of time-averaged streaks. It is also consistent with a Weber's law device. When motion noise was added to the displays, the planar response surface again fitted well, although the residuals showed the presence of a speed energy mechanism. We conclude that a unitary motion mechanism exists (nonideal observer model), although its performance may be supplemented by other mechanisms whose main impact is on discrimination of speeds near zero.     

The Li stance on precipitation in Al–Li-based alloys: an investigation by X-ray Raman spectroscopy

Journal of Materials Science - Decomposition and precipitation processes in a binary Al–Li alloy and a technical Al–Li–Cu–Mg alloy were investigated using differential...     

Decarbonising road freight: Is truck automation and platooning an opportunity?

Clean Technologies and Environmental Policy - Governments, industry and academia are paying high attention to autonomous vehicles and platooning, due to their high potential to transform public and...     

ESD On-Wafer Characterization: Is TLP Still the Right Measurement Tool?

The electrical characterization of devices and circuits regarding their electrostatic discharge (ESD) robustness is done by using several measurement tools. Transmission line pulsing (TLP) and human body model (HBM) testing are the commonly used methods. In this paper, TLP and HBM on-wafer setups are presented regarding their electrical schematics, the type of data that is obtained, and the required calibration methodologies. By using three case studies, both test methods are compared by showing their advantages and disadvantages. It is demonstrated that pulsed measurement methods like TLP testing are not always a suitable tool to fully assess the ESD performance of devices or circuits.     

Innovation and Firm Growth: Is R&D Worth It?

The paper contributes to an emerging literature that critically questions the degree to which R&D, at the centre of national and transnational innovation policies, results in firm growth. The differences in how innovation affects firm growth is explored for small and large publicly quoted US pharmaceutical firms between 1950 and 2008. We observe that the positive impact of R&D on firm growth is highly conditional upon a combination of firm-specific characteristics such as firm size, patenting and persistence in patenting. For small firms, R&D boosts growth for only a subset of firms: namely, those that patent persistently for a minimum of five years. For large pharmaceutical firms, on the other hand, R&D may have a negative impact on growth; potentially resulting from the low R&D productivity these firms have suffered from since the mid-1990s. These results raise important issues around the R&D and firm growth relationship for small and large firms as well the role of persistence in innovation for boosting firm performance.