Energy dissipation of a friction damper: experimental validation

Friction is frequently seen as an unwanted phenomenon whose influence has to be either minimised orcontrolled. In this work one of the positive sides of friction is investigated: friction damping. The frictioninherently present in a system can be positively used to increase the total damping or alternatively, a frictiondamper can be designed. Friction dampers can be a cheap and efficient way to reduce the vibration levels ofa wide range of mechanical systems.In the present paper the conclusions of previous analytic and numericalresults regarding friction damping are validated with results of laboratory experiments, where the energydissipated through friction is measured. The test set-up consists of a mass sliding on parallel ball-bearings,where additional friction is created by a sledge attached to the mass, which is pre-stressed against a frictionplate. No care has been taken to ensure pure dry (Coulomb) friction. Nevertheless, the measured energydissipation is in good agreement with the theoretical results for Coulomb friction

Energy dissipation of a friction damper: experimental validation

Friction is frequently seen as an unwanted phenomenon whose influence has to be either minimised orcontrolled. In this work one of the positive sides of friction is investigated: friction damping. The frictioninherently present in a system can be positively used to increase the total damping or alternatively, a frictiondamper can be designed. Friction dampers can be a cheap and efficient way to reduce the vibration levels ofa wide range of mechanical systems.In the present paper the conclusions of previous analytic and numericalresults regarding friction damping are validated with results of laboratory experiments, where the energydissipated through friction is measured. The test set-up consists of a mass sliding on parallel ball-bearings,where additional friction is created by a sledge attached to the mass, which is pre-stressed against a frictionplate. No care has been taken to ensure pure dry (Coulomb) friction. Nevertheless, the measured energydissipation is in good agreement with the theoretical results for Coulomb friction

A Layman's guide to SUSY GUTs

The determination of the most straightforward evidence for the existence of the Superworld requires a guide for non-experts (especially experimental physicists) for them to make their own judgement on the value of such predictions. For this purpose we review the most basic results of Super-Grand unification in a simple and clear way. We focus the attention on two specific models and their predictions. These two models represent an example of a direct comparison between a traditional unified-theory and a string-inspired approach to the solution of the many open problems of the Standard Model. We emphasize that viable models must satisfy {\em all} available experimental constraints and be as simple as theoretically possible. The two well defined supergravity models, $SU(5)$ and $SU(5)\times U(1)$, can be described in terms of only a few parameters (five and three respectively) instead of the more than twenty needed in the MSSM model, \ie, the Minimal Supersymmetric extension of the Standard Model. A case of special interest is the strict no-scale $SU(5)\times U(1)$ supergravity where all predictions depend on only one parameter (plus the top-quark mass). A general consequence of these analyses is that supersymmetric particles can be at the verge of discovery, lurking around the corner at present and near future facilities. This review should help anyone distinguish between well motivated predictions and predictions based on arbitrary choices of parameters in undefined models.Comment: 25 pages, Latex, 11 figures (not included), CERN-TH.7077/93, CTP-TAMU-65/93. A complete ps file (1.31MB) with embedded figures is available by request from [email protected]

Composite Fermions with Orbital Magnetization

For quantum Hall systems, in the limit of large magnetic field (or equivalently small electron band mass $m_b$), the static response of electrons to a spatially varying magnetic field is largely determined by kinetic energy considerations. This response is not correctly given in existing approximations based on the Fermion Chern-Simons theory of the partially filled Landau level. We remedy this problem by attaching an orbital magnetization to each fermion to separate the current into magnetization and transport contributions, associated with the cyclotron and guiding center motions respectively. This leads to a Chern-Simons Fermi liquid description of the $\nu=\frac{1}{2m}$ state which correctly predicts the $m_b$ dependence of the static and dynamic response in the limit $m_b \rightarrow 0$.Comment: 4 pages, RevTeX, no figure

An Illustrated Record and Range Extension of Caligus chelifer (Copepoda, Siphonostomatoida) in the Gulf of Mexico

A male specimen of the copepod Caligus chelifer Wilson, 1905, was collected during a plankton survey carried out during February 1994 off the Mexican coasts of the eastern Gulf of Mexico (Tamaulipas state). This is the first record of this species in Mexican waters and south of the 25ºN in the Northwestern Atlantic. Taxonomic illustrations of the specimen are provided

Human papillomavirus E2 regulates SRSF3 (SRp20) to promote capsid protein expression in infected differentiated keratinocytes

The human papillomavirus (HPV) life cycle is tightly linked to differentiation of the infected epithelial cell suggesting a sophisticated interplay between host cell metabolism and virus replication. Previously we demonstrated in differentiated keratinocytes in vitro and in vivo that HPV16 infection caused increased levels of the cellular SR splicing factors (SRSFs) SRSF1 (ASF/SF2), SRSF2 (SC35) and SRSF3 (SRp20). Moreover, the viral E2 transcription and replication factor that is expressed at high levels in differentiating keratinocytes could bind and control activity of the SRSF1 gene promoter. Here we reveal that E2 proteins of HPV16 and HPV31 control expression of SRSFs 1, 2 and 3 in a differentiation-dependent manner. E2 has the greatest trans-activation effect on expression of SRSF3. siRNA depletion experiments in two different models of the HPV16 life cycle (W12E and NIKS16) and one model of the HPV31 life cycle (CIN612-9E) revealed that only SRSF3 contributed significantly to regulation of late events in the virus life cycle. Increased levels of SRSF3 are required for L1 mRNA and capsid protein expression. Capsid protein expression was regulated specifically by SRSF3 and appeared independent of other SRSFs. Taken together these data suggest a significant role of the HPV E2 protein in regulating late events in the HPV life cycle through transcriptional regulation of SRSF3 expression. IMPORTANCE Human papillomavirus replication is accomplished in concert with differentiation of the infected epithelium. Virus capsid protein expression is confined to the upper epithelial layers so as to avoid immune detection. In this study we demonstrate that the viral E2 transcription factor activates the promoter of the cellular SRSF3 RNA processing factor. SRSF3 is required for expression of the E4̂L1 mRNA and so controls expression of the HPV L1 capsid protein. Thus we reveal a new dimension of virus-host interaction crucial for production of infectious virus. SRSF proteins are known drug targets. Therefore, this study provides an excellent basis for developing strategies to regulate capsid protein production in the infected epithelium and production of new virions

Engage D2.1 Communication plan, website, and visual identity material

The purpose of this document, Deliverable 2.1, is to describe the dissemination plan, dissemination policy and initial dissemination products of the SESAR 2020 Exploratory Research action Engage, taking into account its specifications and the target audience. The following pages document the corresponding tasks involved in D2.1

Number of Generations in Free Fermionic String Models,

In string theory there seems to be an intimate connection between spacetime and world-sheet physics. Following this line of thought we investigate the family problem in a particular class of string solutions, namely the free fermionic string models. We find that the number of generations $N_g$ is related to the index of the supersymmetry generator of the underlying $N=2$ internal superconformal field theory which is always present in any $N=1$ spacetime supersymmetric string vacuum. We also derive a formula for the index and thus for the number of generations which is sensitive to the boundary condition assignments of the internal fermions and to certain coefficients which determine the weight with which each spin-structure of the model contributes to the one-loop partition function. Finally we apply our formula to several realistic string models in order to derive $N_g$ and we verify our results by constructing explicitly the massless spectrum of these string models.Comment: 17 pages, Plain Tex, no figures

Dual Response Models for the Fractional Quantum Hall Effect

It is shown that the Jain mapping between states of integer and fractional quantum Hall systems can be described dynamically as a perturbative renormalization of an effective Chern-Simons field theory. The effects of mirror duality symmetries of toroidally compactified string theory on this system are studied and it is shown that, when the gauge group is compact, the mirror map has the same effect as the Jain map. The extrinsic ingredients of the Jain construction appear naturally as topologically non-trivial field configurations of the compact gauge theory giving a dynamical origin for the Jain hierarchy of fractional quantum Hall states.Comment: 8 pages LaTe