Hot water cooled electronics: Exergy analysis and waste heat reuse feasibility

We report an experimental study on exergetically efficient electronics cooling using hot water as coolant. It is shown that water temperatures as high as 60 °C are sufficient to cool microprocessors with over 90% first law (energy based) efficiency. The chip used in our experiment is kept at temperatures of 80 °C or below so as not to exceed any allowable industrial specifications for maximum microprocessor chip temperature. The use of hot water as coolant will eliminate the requirement for chillers typically used in air-cooled data centers and, therefore, significantly reduce the power consumption. An exergy analysis shows that a six fold rise in second law (exergy based) efficiency is achieved by switching the water inlet temperature from 30 °C to 60 °C. The resulting high exergy at the heat sink outlet is a measure of the potential usefulness of the waste heat of data centers, thereby helping to design data centers with minimal carbon footprint. A new metric for the economic value of the recovered heat, based on costs for electricity and fossil fuels, heat recovery efficiency and an application specific utility function, is introduced to underscore the benefits of hot water cooling. This new concept shows that the economic value of the heat recovered from data centers can be much higher than its thermodynamic value.     

Electrical Detection of Spin Precession in Freely Suspended Graphene Spin Valves on Cross‐Linked Poly(methyl methacrylate)

Spin injection and detection is achieved in freely suspended graphene using cobalt electrodes and a nonlocal spin‐valve geometry. The devices are fabricated with a single electron‐beam‐resist poly(methyl methacrylate) process that minimizes both the fabrication steps and the number of (aggressive) chemicals used, greatly reducing contamination and increasing the yield of high‐quality, mechanically stable devices. As‐grown devices can present mobilities exceeding 10⁴ cm² V^?1 s^?1 at room temperature and, because the contacts deposited on graphene are only exposed to acetone and isopropanol, the method is compatible with almost any contacting material. Spin accumulation and spin precession are studied in these nonlocal spin valves. Fitting of Hanle spin precession data in bilayer and multilayer graphene yields a spin relaxation time of ～125‐250 ps and a spin diffusion length of 1.7‐1.9 μm at room temperature.     

His-tags as Zn(II) binding motifs in a protein-based fluorescent sensor

Fluorescent indicators that allow real-time imaging of Zn(II) in living cells are invaluable tools for understanding Zn(II) homeostasis. Genetically encoded sensors based on fluorescence resonance energy transfer between fluorescent protein domains have important advantages over synthetic probes. We discovered that hexahistidine tags have a strong tendency to dimerize upon binding of Zn(II) in solution and we used this principle to develop a new protein-based sensor for Zn(II). Enhanced cyan and yellow fluorescent proteins were connected by long flexible peptide linkers and His-tags were incorporated at both termini of this fusion protein. The resulting sensor CLY9-2His allows the ratiometric fluorescent detection of Zn(II) in the nanomolar range. In addition, CLY9-2His is selective over the physiologically relevant metal ions Fe(II), Mn(II), Ca(II) and Mg(II). Our approach demonstrates the potential of using small peptides as metal-binding ligands in chelating fluorescent protein chimeras.     

Scratching polycarbonate: A quantitative model

Generally it is understood that friction is additively decomposed into an adhesion- and a deformation-related component, suggesting independence. Experimentally these components cannot be separated and only by combining experiments with simulations, a decoupled analysis is possible. We apply this hybrid experimental–numerical approach in the single-asperity scratch test, simplifying the friction geometry. Simulations without adhesive interaction between tip and surface result in friction forces that are only half of the experimental ones, and are almost not influenced by the sliding velocity. In case of an additive decomposition, this would imply a large contribution of the adhesive component which, moreover, should take care of all rate dependency. This sounds unrealistic. By inclusion of constant friction between tip and polymer, we find that the adhesive component strongly influences the contribution of the deformation component by the formation of a bow wave in front of the sliding tip. Experimental friction forces are quantitatively predicted, including the rate dependency. This entails that the suggested additive decomposition is not applicable and the large macroscopic deformation response proves to be the result of small changes in local processes. Using the model, for the first time, quantitative relations between the polymer's intrinsic mechanical properties and its frictional properties are established.     

Arginine metabolism in sugar deprived Lactococcus lactis enhances survival and cellular activity, while supporting flavour production

Flavour development in cheese is affected by the integrity of Lactococcus lactis cells. Disintegrated cells enhance for instance the enzymatic degradation of casein to free amino acids, while integer cells are needed to produce specific flavour compounds from amino acids. The impact of the cellular activity of these integer cells on flavour production remains to be elucidated. In this study we investigated whether lactose-deprived L. lactis cells that use arginine as an alternative energy source can extend cellular activity and produce more specific flavours. In cheese experiments we demonstrated that arginine metabolising cells survived about 3 times longer than non-arginine metabolising cells, which suggests prolonged cellular activity. Cellular activity and flavour production of L. lactis was further studied in vitro to enable controlled arginine supplementation. Comparable with the results found in cheese, the survival rates of in vitro incubated cells improved when arginine was metabolised. Furthermore, elongated cellular activity was reflected in 3-4-fold increased activity of flavour generating enzymes. The observed prolonged cellular activity resulted in about 2-fold higher concentrations of typical Gouda cheese flavours. These findings provide new leads for composing starter cultures that will produce specific flavour compounds.     

PBDEs in European background soils: levels and factors controlling their distribution

Surface soils (0-5 cm) from remote/rural woodland (coniferous and deciduous) and grassland locations on a latitudinal transectthrough the United Kingdom and Norway were analyzed for polybrominated diphenyl ethers (PBDEs). Concentrations ranged between 65 and 12 000 sigma(ALL)PBDE ng kg(-1) dry weight. PBDE-47, -99, -100, -153, and -154-the major constituents of the penta-BDE technical product-dominated the average congener pattern of the soils. Indeed, the average congener composition and distribution measured in these European background soils closely matched that reported in the technical penta-BDE product. This is interpreted as evidence that transfer of the congeners present in penta-BDE-treated products from source-air-soil occurs with broadly similar efficiency, perhaps because there has been little weathering/degradation/alteration of the congener source pattern by processes operating during atmospheric transport or within the soil itself. BDE-183, a marker for the octa-BDE mix, was detected at concentrations ranging from <9 to 7000 (median approximately 50 ng kg(-1)). In most soils, it made a minor contribution to the sigma(ALL)PBDE concentration, but it was a major component in some samples from northern England. Forest soils tended to have higher concentrations than grasslands. Underlying the average soil composition, some differences in the congener pattern were observed. Notably, there was evidence of latitudinal fractionation, with the relative contribution of PBDE-47 and lighter congeners to the sigmaPBDE increasing northwards (with increasing distance from source areas), while the proportion of PBDE-99 and heavier congeners decreased. Plots of concentration against percentage soil organic matter had different slopes for different congeners. Higher slopes were generally seen for the lighter PBDEs (e.g., PBDE-47), indicating that they have undergone some air-surface exchange (hopping), while the slopes of heavier congeners (e.g., PBDE-153) were close to zero, indicating that they are retained more effectively by soils after deposition.     

An evaluation of the Brief Symptom Inventory–18 using item response theory: Which items are most strongly related to psychological distress?

The psychometric structure of the Brief Symptom Inventory–18 (BSI-18; Derogatis, 2001) was investigated using Mokken scaling and parametric item response theory. Data of 487 outpatients, 266 students, and 207 prisoners were analyzed. Results of the Mokken analysis indicated that the BSI-18 formed a strong Mokken scale for outpatients and prisoners, indicating strong unidimensionality. For students, only the depression and anxiety items formed a medium Mokken scale. Parametric item response theory analyses showed that the best discriminating items came from the depression and anxiety subscales. (PsycINFO Database Record (c) 2011 APA, all rights reserved)