Biocompatibility and tissue regenerating capacity of crosslinked dermal sheep collagen

The biocompatibility and tissue regenerating capacity of four crosslinked dermal sheep collagens (DSC) was studied. In vitro, the four DSC versions were found to be noncytotoxic or very low in cytoxicity. After subcutaneous implantation in rats, hexamethylenediisocyanatecrcrosslinked DSC (HDSC) seldom induced an increased infiltration of neutrophils or macrophages, as compared with normal wound healing; whereas new formation of collagen was observed. DSC crosslinked with glutaraldehyde (GDSC) followed by reaction with NaBH4 shortly after implantation showed an increased infiltration of neutrophils with a deviant morphology. Furthermore, a high incidence of calcification was observed, which may explain the minor ingrowth of giant cells and fibroblasts, and the poor formation of new rat collagen. Acyl azide-crosslinked DSC (AaDSC) first induced an increased infiltration of macrophages, and then of giant cells, both with high lipid formation. AaDSC degraded at least twice as slowly as HDSC and GDSC, finally leaving a matrix of newly formed rat collagen. Samples crosslinked with 1-ethyl-3-(3-dimethylaminopropyl)carbodiimide hydrochloride and N-hydroxysuccinimide (ENDSC) induced the same mild cellular reaction as HDSC; whereas, similar to AaDSC, the degradation rate was slow and an optimal rat collagen matrix was formed. Of the crosslinked DSC samples, ENDSC seems most promising for tissue regeneration

Some comments on Laplacian gauge fixing

Laplacian gauge fixing was introduced to find a unique representative of the gauge orbit, which on the lattice could be implemented by a ``finite'' algorithm. What was still lacking was a perturbative formulation of this gauge, which will be presented here. However, renormalizability is still to be demonstrated. For torodial and spherical geometries a detailed comparison with the Landau (or Coulomb) gauge will be made.Comment: Contribution to Lattice '94, 3 pages PostScrip

The importance of internal communication in organizational change: Case study of the structural change in a Belgian government agency

Internal communication is an essential element to create willingness to change in organizations (Elving 2005a, 2005b; Clampitt et al. 2000; Armenakis et al. 2007). In this paper, we present the results of a mixed method research assessing change communication in a Belgian governmental institution which recently implemented a change in its organizational structure. Our approach to the data was twofold. The descriptive, quantitative first part of the research relies on a survey of 718 staff members involved in the change. The survey consists of 30 questions assessing the internal communication about the change, and the staff’s willingness to change. The questionnaire is based on existing instruments - such as the ICA audit, the scales of Armenakis et al (2007) and Wanous et al (2000). We addressed the following research questions: RQ1 - To what extent are staff members willing to go along with the change? RQ2 - To what extent are staff members satisfied with the internal communication regarding the change? Second, we conducted 14 semi-structured in-depth interviews with staff members, in which we further explored notable findings of the survey. The interviews (each about 20 to 30 minutes) were conducted in the period from June 25, 2014 to July 9, 2014 and aimed at answering the following research question: RQ3 - To what extent has the internal communication had an impact on staff members’ willingness to change or change resistance ? Our findings confirm that a negative assessment of the internal communication correlates with a higher degree of change resistance, but also -if not more so- the results reveal the the extent to which individual self interest acts cause resistance to change. In conclusion, we open up the debate about the role of internal communication in signaling and preventing this from happening. __________ 50-word summary: This paper presents the results of a mixed method research assessing change communication in a Belgian governmental institution which recently implemented a change in its organizational structure. The main finding is that a crucial role is reserved for internal communication in preventing self-interest acts as a brake on change readiness

The reception of relativity in the Netherlands

This article reviews the early academic and public reception of Albert Einstein's theory of relativity in the Netherlands, particularly after Arthur Eddington's eclipse experiments of 1919. Initially, not much attention was given to relativity, as it did not seem an improvement over Hendrik A. Lorentz' work. This changed after the arrival in Leiden of Paul Ehrenfest. Soon relativity was much studied and lead to controversy among a number of conservative intellectuals, as elsewhere in Europe. The tone of Dutch critics was much more mild, however. This can be understood when one considers Dutch neutrality during World War I. Einstein's political positions were generally positively perceived in Holland, which Dutch academics put to use in their efforts at international reconciliation abroad, and the presentation of theoretical physics at home

Rudder roll stabilization for ships

This paper describes the design of an autopilot for rudder roll stabilization for ships. This autopilot uses the rudder not only for course keeping but also for reduction of the roll. The system has a series of properties which make the controller design far from straightforward: the process has only one input (the rudder angle) and two outputs (the heading and the roll angle); the transfer from rudder to roll is non-minimum-phase; because large and high-frequency rudder motions are necessary, the non-linearities of the steering machine cannot be disregarded; the disturbances caused by the waves vary considerably in amplitude and frequency spectrum.\ud \ud In order to solve these problems a new approach to the LQG method has been developed. The control algorithms were tested by means of computer simulations, scale-model experiments and full-scale trials at sea. The results indicate that a rudder roll stabilization system is able to reduce the roll as well as a conventional fin stabilization system, while it requires less investments. Based on the results obtained in this project the Royal Netherlands Navy has decided to implement rudder roll stabilization on a series of ships under construction at this moment

Not only the butterflies: managing ants on road verges to benefit Phengaris (Maculinea) butterflies

Obligate myrmecophilic butterfly species, such as Phengaris (Maculinea) teleius and P. nausithous, have narrow habitat requirements. Living as a caterpillar in the nests of the ant species Myrmica scabrinodis and M. rubra, respectively, they can only survive on sites with both host ants and the host plant Great Burnet Sanguisorba officinalis. After having been reintroduced into a nature reserve in the Netherlands in 1990, both butterfly species expanded their distribution to linear landscape elements such as road verges and ditch edges outside this reserve. As additional habitat of both butterfly species, vegetation management of these landscape elements became important. Our results show that a management beneficial for Phengaris butterflies should aim to increase the nest density of Myrmica species, at the same time reducing the density of nests of the competitor Lasius niger or at least keeping them at a low density. Unfavourable grassland management under which L. niger thrives, includes not mowing or flail-cutting the grass, or depositing dredgings along the side of the ditch. Management favourable for the two Myrmica species differs, demanding some flexibility if both species are to benefit. M. scabrinodis is best supported with early mowing of the road verge vegetation or late mowing in the nature reserve, both of which result in an open vegetation and warm microclimate. In contrast, the nest sites of M. rubra should be left undisturbed during the summer, and mown in late autumn. Mowing of butterfly habitat should be avoided between mid-June and mid-September as this would remove the flowerheads of the Sanguisorba plants, on which the butterflies lay their eggs

Towards Meson Spectroscopy Instead of Bump Hunting

Mesonic resonances are generally observed in data as narrow, moderately broad, or wide peaks in scattering or production processes. In the eyes of nearly all experimentalists, any suchlike bump is a true resonance as soon as its statistical significance exceeds certain minimal values. However, this simple point of view ignores possible effects from competing hadronic channels and the opening of the corresponding thresholds. On the other hand, most theoretical hadron-model builders consider mesons merely bound states of a quark and an antiquark, or of more exotic combinations sometimes involving valence gluons as well. Also the latter description is much too naive, since considerable mass shifts or even the dynamical generation of extra states due to unquenching are equally ignored. In the present paper, a largely empirical yet very successful approach to meson spectroscopy is revisited, in which all the above phenomena can be accounted for non-perturbatively, with concrete examples of some enigmatic mesonic states described in detail. First, the X(4260) charmonium enhancement is argued to be a non-resonant structure resulting from depletion effects due to competing channels and resonances. Then, the X(3872) charmonium-like meson is described as a unitarised $J^{PC}=1^{++}$ $c\bar{c}$ state. Also, the unusual pattern of masses and widths of the open-charm axial-vector mesons $D_1(2420)$, $D_1(2430)$, $D_{s1}(2536)$, and $D_{s1}(2460)$ is shown to follow from highly non-perturbative coupled-channel and mixing effects. Finally, first indications of a very light scalar boson are presented, on the basis of published BABAR data.Comment: Invited seminar given by G. Rupp at the International School of Nuclear Physics, 33rd course: "From Quarks and Gluons to Hadrons and Nuclei", Erice, Sicily, Italy, 16 - 24 September 2011; 7 pages, 5 figures (9 plots), style of Progress in Particle and Nuclear Physic

Optimal clustering of frequency-constrained maintenance jobs with shared set-ups

Since maintenance jobs often require one or more set-up activities, joint execution or clustering of maintenance jobs is a powerful instrument to reduce shut-down costs. We consider a clustering problem for frequency-constrained maintenance jobs, i.e. maintenance jobs that must be carried out with a prescribed (or higher) frequency. For the clustering of maintenance jobs with identical, so-called common set-ups, several strong dominance rules are provided. These dominance rules are used in an efficient dynamic programming algorithm which solves the problem in polynomial time. For the clustering of maintenance jobs with partially identical, so-called shared set-ups, similar but less strong dominance rules are available. Nevertheless, a surprisingly well-performing greedy heuristic and a branch and bound procedure have been developed to solve this problem. For randomly generated test problems with 10 set-ups and 30 maintenance jobs, the heuristic was optimal in 47 out of 100 test problems, with an average deviation of 0.24% from the optimal solution. In addition, the branch and bound method found an optimal solution in only a few seconds computation time on average

Monte Carlo calculation for systems consisting of several coordinate patches

I investigate the time step dependence of Monte Carlo simulations for coordinate-spaces consisting of several patches. It is shown that a naive kinetic term does not necessarily converge to the same spectrum as a Hamiltonian calculation. Then an improved kinetic term is presented which allows one to connect the Monte Carlo and Rayleigh-Ritz results of intermediate volume SU(2) gauge theory.Comment: 18 page

An infrared investigation of the catalyst formation in the system Ni(acac)2, C3H4, (iBu)3AL for propadiene polymerization

The catalyst formation in the system Ni(acac)2, C3H4, (iBu)3Al was investigated by means of infrared spectroscopy. It was found that the Al(acac)3 and (iBu)2Al(acac) formed are both by-products of catalyst formation without a catalytic activity. Ni(acac)2 loses its acac groups forming the unstable (iBu)2Ni compound; without C3H4 being present, this compound disproportionates to Ni metal and isobutane and isobutene. In the presence of C3H4 an allyl-nickel complex is formed, which reacts with (iBu)3Al to give the actual catalyst, possibly a bimetallic allyl—nickel-aluminium complex. Catalysts such as Ni(acac)2, C3H4, (iBu)3Al and (πC3H5)2Ni with or without (iBu)3Al all selectively give 1, 2, 1, 2-polypropadiene. A Lewis base like pyridine not only decreases the polymerization rate but also changes the selectivity towards the formation of 1, 2, 2, 1-polymer