Is there a place for a mock <Emphasis Type="Italic">h</Emphasis>-index?

The h-index has captured the imagination of scientometricians and bibliometricians to such an extent that one can now divide the history of the subject virtually into a pre-Hirsch and a post-Hirsch period. Beyond its academic value, it is now used as a tool for research assessment of individuals, research faculties and institutions and even for comparing performance of journals and countries. Since its introduction, many Hirsch-type variants have been proposed to overcome perceived limitations of the original index. In this paper, using ideas from mathematical modeling, another mock h-index is proposed which may complement the h-index and give it better resolving power.     

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.     

Is there a universal log law for turbulent wall-bounded flows?

The history and theory supporting the idea of a universal log law for turbulent wall-bounded flows are briefly reviewed. The original idea of justifying a log law from a constant Reynolds stress layer argument is found to be deficient. By contrast, it is argued that the logarithmic friction law and velocity profiles derived from matching inner and outer profiles for a pipe or channel flow are well-founded and consistent with the data. But for a boundary layer developing along a flat plate it is not, and in fact it is a power law theory that seems logically consistent. Even so, there is evidence for at least an empirical logarithmic fit to the boundary-friction data, which is indistinguishable from the power law solution. The value of kappa approximately 0.38 obtained from a logarithmic curve fit to the boundary-layer velocity data, however, does not appear to be the same as for pipe flow for which 0.43 appears to be the best estimate. Thus, the idea of a universal log law for wall-bounded flows is not supported by either the theory or the data.     

Nanoclusters – Building Blocks for Future Nanoelectronic Devices?

Ligand stabilized metal nanoclusters in the size range of 1–2 nanometers exhibit well pronounced quantum size behaviour, even at room temperature. This is due to the development of discrete energy levels in those metal particles which are reduced in size to quasi zero‐dimensionality. Quantum mechanically they can be considered as big atoms. Studies of the current‐voltage (I‐U) characteristics identified these clusters as single electron transistors and herewith as highly promising candidates as building blocks in future nanoelectronics. As a condition, the clusters – here it is especially Au₅₅(PPh₃)₁₂Cl₆ – have to be organized in two and one dimensions. Procedures have been developed to generate well ordered cluster monolayers by self assembling. Quasi one‐dimensional cluster wires became available by degradation of monolayers by means of modified Langmuir‐Blodgett techniques. Very first electrical investigations of short cluster wires indicate them as quantum mechanically determined units.     

Is there a thickness effect on compressive strength of unnotched composite laminates?

The effect of laminate thickness was investigated on the compressive behavior of unidirectional and crossply composites. A recently developed compression test method for thick composites was used to test specimens from 16 to 200-plies thick. In all cases the stress-strain behavior to failure is nonlinear and failure strength is matrix dominated. Longitudinal compressive failure is triggered by matrix failure accompanied by fiber microbuckling and the compressive strength is greatly degraded by initial fiber misalignment. The longitudinal compressive strength shows a mild trend of decreasing values with increasing thickness. It can be explained that, even if such a trend is significant, increasing size would have a diminishing effect on compressive strength for initial fiber misalignments greater than 1.5 to 2°. This revised version was published online in July 2006 with corrections to the Cover Date.     

Sind die genormten Prüfverfahren für zügige und schlagartige Beanspruchung noch zeitgemäß? – Neue Wege zur Dimensionierung –

Are the Standardized Methods of Testing Tensile and Impact Loads still up to Date? – New Ways of Dimensioning – Test specifications for polymer materials are derived from proven and standardized mechanical test methods used for determining the properties of metal materials. Having established that, apart from long-term testing methods, it is impossible to derive any dimensioning characteristic data from most test methods, the picture is very unsatisfactory indeed. Added to this is the fact that, in order to determine long-term properties, extremely time-consuming test methods (some-times lasting for more than one year) must be applied and that, in order to measure stresses in the short-term and impact loading range, it is impossible to do without experiments on practical building components involving complex technical measurements. This paper takes a critical look at these two groups of problems and puts forward fresh possibilities.

• dimensioning under impact load
• calculation of the long-term behaviour from short-term tensile tests.

For amorphous plastics, we get, with decreasing time under load (< 1 s) and decreasing temperatures, a transition from semi-tough to brittle material behaviour. For PMMA, an elongation at break threshold appears to exist at 2.2% and a threshold loadability at 135 N/mm² in the region of impact loads. These values can be taken as a basis for dimensioning against impact. For most other thermoplastics examined here, the tendencies are the same, although exact thresholds cannot be given yet. It is also possible, from the curve of the shear modulus and mechanical loss factor as a function of temperature, to estimate a Young's modulus threshold, which shows good conformity with data measured in actual practice. For PMMA, the value is approx. 6,500 N/mm². Form shear modulus and attenuation curves, it is also possible to estimate how dependent on velocity and temperature the mechanical properties of a material are (tough/brittle transition). Finally, it can be shown that it even seems possible, using the test method presented here, to draw conclusions from very short-term tests (< 17 min.) about the long-term strength. The reason why the standardized short-term tensile test does not provide any characteristic material data suitable for the dimensioning is, in our opinion, that the major test condition, the strain rate, is not constant. Tests with constant strain rates, on the other hand, provide a readily describable deformation behaviour with which it is even possible to predict the long-term behaviour. In addition, scattering of the measurements is reduced in a remarkable manner. On varying the testing temperature, we get material data with which the time-temperature shifting principle leads to excellent agreement with results of earlier tests. In this way, we geht from short-term tests - at present, because of the fundamental nature of the tests, times of approx. 100 h are needed, though there are plans for a maximum testing time of 10 h in future - at various temperatures a picture of the material behaviour, which corresponds very well with the longterm behaviour. It even seems to be possible to predict the creep behaviour and obtain information about the load-bearing capacity, e.g. of weld seams, in the required dimensioning time of many thousands of hours.     

Transparentes leitfähiges TiO2:Nb – ein TCO‐Material der Zukunft?

Transparent conductive TiO₂:Nb – a TCO material of the future? Niobium doped titania is a widely unknown TCO material. We present the results of TiO₂:Nb thin films deposited by DC and pulse DC sputtering from a ceramic titania target with a content of approximately 6 wt.‐percent Nb in a pilot scale in‐line sputtering plant. With DC sputtering on Borofloat 33 substrate a 100 nm thin film show after annealing at 450 °C a resistivity of 7.2 × 10^?4 Ωcm with a low extinction coefficient of 0.02 and a transmittance in the visible range of 74.8%.     

Do ‘Functional Barriers’ Function?

The direct recycling of plastics (food grade plastic to food grade plastic) obviously gives rise to possible health hazards. Contaminants, picked up by the material during first usage, may migrate into food during second use. ‘Functional barrier’ layers have been used for a long time (e.g. aluminium, silica and silicates), but there is now considerable research and development on ‘barrier’ layers of plastics for the purpose. For technological and regulatory reasons, use of the same plastic in virgin form as the recyclate is favoured. A theoretical study shows that such a layer, in general, must function more as a sponge than a barrier. Moreover, in general, migration into and through the barrier must start at manufacture of the package, and not at containment of the food (as assumed in all legislation). Although in some instances there may be adequate delay and reduction of migration to ensure safety, this is not so in general and certainly cannot be guaranteed. Hence the concept needs reconsideration in the interest of public safety.     

Internationalization of academic journals: Is there still a gap between social and natural sciences?

In this study we compare internationalization of academic journals in six fields of science. Internationalization was investigated through journals’ concentration on publishing papers from particular countries, relationship between the geographical distributions of editors and authors, and relationship between language of publication and the geographical distribution of papers. Having analyzed more than 1,000 journals we can state that social sciences literature in the fields considered is still nationally and linguistically fragmented more than natural sciences literature, but in some cases the gap is not so big. One of the consequences concerning research output assessment is that usefulness of international databases having national disparity in coverage is still limited in social sciences.     

Is hepcidin‐25 a predictor of atherosclerosis in hemodialysis patients?

Atherosclerotic cardiovascular disease is an important cause of mortality and morbidity in hemodialysis patients. Iron accumulation in arterial wall macrophages is increased in atherosclerotic lesions. Hepcidin is a key hepatic hormone regulating iron balance. It inhibits iron release from macrophages and iron absorption from enterocytes by binding and inactivating the cellular iron exporter ferroportin. The aim of this study is to investigate the relation of hepcidin‐25, iron parameters, and atherosclerosis measured by carotid intima media thickness (CIMT) in hemodialysis patients. Eighty‐two hemodialysis patients were enrolled in this cross‐sectional study. Predialysis blood samples were centrifuged at 1500 g and 4°C for 10 minutes and stored at ?80°C for the measurement of hepcidin‐25. DRG hepcidin enzyme‐linked immunosorbent assay kit was used for the measurement of hepcidin‐25. Ultrasonographical B‐mode imaging of bilateral carotid arteries was performed with a high‐resolution real‐time ultrasonography (Mindray DC7). Mean age of the study population was 57.90 ± 16.08 years and 43.9% were men. Total study population was grouped into two according to median value of hepcidin‐25. There was no difference between groups with respect to age, dialysis vintage, and C‐reactive protein. CIMT was found to be statistically significantly higher in low hepcidin‐25 group. In correlation analysis, CIMT was found to be correlated with age (P < 0.01, R = 0.33) and hepcidin‐25 (P < 0.01, R = 0.46). In linear regression analysis, age (β = 0.31) and hepcidin‐25 (β = 0.44) were found to be the determinants of CIMT in hemodialysis patients. Our results implicate that hepcidin may take part in pathophysiology of atherosclerosis and cardiovascular disease in hemodialysis patients.     

Is there ferromagnetic to spin-glass transition in PdAuFe alloys?

Electrical resistivity studies on several (Pd_1–x Au _x )_99.93Fe_0.07 alloys between 25 mK and 1 K are reported. The experiments reveal interesting features of the impurity spin polarization with the addition of Au atoms to pure PdFe_0.07 alloy. Forx<0.28 the ternary alloys exhibit a familiarT ² dependence for belowT _c , indicative of complex magnetic behavior. For still higher Au concentrations, resistivity maxima occur in these alloys, reflective of short-range magnetic ordering. Arguments are presented to show that this is strongly suggestive of spin-glass-type freezing at lower temperatures, as is observed in many canonical metallic spin-glasses.     

Is the diatom sex clock a clock?

The unique life cycle of diatoms with continuous decreasing and restoration of the cell size leads to periodic fluctuations in cell size distribution and has been regarded as a multi-annual clock. To understand the long-term behaviour of a population analytically, generic mathematical models are investigated algebraically and numerically for their capability to describe periodic oscillations. Whereas the generally accepted simple concepts for the proliferation dynamics do not sustain oscillating behaviour owing to broadening of the size distribution, simulations show that a proposed limited lifetime of a newly synthesized cell wall slows down the relaxation towards a time-invariant equilibrium state to the order of a hundred thousand generations. In combination with seasonal perturbation events, the proliferation scheme with limited lifetime is able to explain long-lasting rhythms that are characteristic for diatom population dynamics. The life cycle thus resembles a pendulum clock that has to be wound up from time to time by seasonal perturbations rather than an oscillator represented by a limit cycle.     

Is there an association between intradialytic hypotension and serum magnesium changes?

Intradialytic hypotension (IDH) is the most common complication of hemodialysis (HD). The aim of this study was to investigate the significance of intradialytic changes of serum magnesium (sMg) and its relation to IDH. We considered 58 patients undergoing HD. Serum magnesium was measured at start, after 2 hours, and at the end of the HD sessions. Total sMg concentration corrected for albumin was according to Krolles proposed formula. Blood pressure was measured every 30 min. Data were analyzed by SPSS.15. A P value of less than 0.05 was considered as significant. Occurrence of IDH among HD patients was 27.6% (16/58). Serum magnesium decreased significantly during HD session (P<0.05). Comparing corrected sMg in IDH group with non-IDH group showed that: corrected sMg was 0.66 ± 0.14 mmol/L vs. 0.84 ± 0.26 mmol/L at the start of dialysis (P=0.43), 0.62 ± 0.17 mmol/L vs. 0.74 ± 0.23 mmol/L (P=0.04) at 2 hours, and 0.61 ± 0.12 mmol/L vs. 0.72 ± 0.22 mmol/L (P=0.03) at the end of dialysis. Intradialytic hypotension episodes were significantly related to a decrease in sMg during dialysis (P=0.02). There was a significant decrease in sMg levels during dialysis. Intradialytic hypotension was significantly related to lowered sMg levels during dialysis.     

Particle‐Based Optical Sensing of Intracellular Ions at the Example of Calcium – What Are the Experimental Pitfalls?

Colloidal particles with fluorescence read‐out are commonly used as sensors for the quantitative determination of ions. Calcium, for example, is a biologically highly relevant ion in signaling, and thus knowledge of its spatio‐temporal distribution inside cells would offer important experimental data. However, the use of particle‐based intracellular sensors for ion detection is not straightforward. Important associated problems involve delivery and intracellular location of particle‐based fluorophores, crosstalk of the fluorescence read‐out with pH, and spectral overlap of the emission spectra of different fluorophores. These potential problems are outlined and discussed here with selected experimental examples. Potential solutions are discussed and form a guideline for particle‐based intracellular imaging of ions.