First test of tiltmeters for the link system of CMS

In this note we present first tests done with the tiltmeters proposed as the key elements of the Laser Level systems to be used in the CMS alignment system. The reponse of the sensors under moderated longitudinal and transversal tilts is studied and intrinsic performance is extracte

Test results of the semitransparent amorphous silicon sensors for the link system of CMS

Semitransparent amorphous silicon sensors have been proposed as the 2D positioning sensors for the link system of the CMS alignment. We have developed a general method to characterise these sensors, from the signal reconstruction to the beam deflection. The transparency for the HeNe wavelength has also been calculated

Accurate coplanarity measurement of a network of points, using linear CCD sensors and a sweeping laser beam

A method for a real time remote accurate coplanarity measurement of a network of points is presented. A light surface, generated by a laser and a rotating pentaprism, is used as a reference plane to which the relative positions of a set of CCD sensors, located on the nodes of the network, are determined. Based on this method, a prototype for the alignment of the CMS detector has been built and tested. Position reconstruction algorithms and experimental test results are presented. The obtained position measurement precision was 10 um up to distances of 6 m

Keratin intermediate filament dynamics in cell heterokaryons reveals diverse behaviour of different keratins

To study the dynamics of keratin intermediate filaments, we fused two different types of epithelial cells (PtK2 and BMGE+H) and studied how the keratins from the parental cells recombine and copolymerize to form the heterokaryon cytoskeleton. The behaviour of the keratins during this process was followed by immunofluorescence using specific antibodies. After fusion, the parental cytoskeletons undergo a depolymerization process most apparent in the region adjacent to the fusion area. The depolymerized subunits spread throughout the heterokaryon and copolymerize into a new hybrid cytoskeleton. The complete process is very rapid, occurring in 3-4 hours, thus demonstrating the highly dynamic nature of the keratin cytoskeleton. Although newly synthesised subunits contribute to the formation of the hybrid cytoskeleton, the process takes place with similar kinetics in the absence of protein synthesis, showing the dynamic nature of the keratins from pre-existing cytoskeletons. During this process, specific keratins behave differently. Keratins K8, K18, K5 and K10 are mobilised from the parental cytoskeletons and reassemble rapidly into the hybrid cytoskeleton (3-6 hours), whereas K14 requires a substantially longer period (9-24 hours). Thus, different keratins, even when they form part of the same heterodimeric/tetrameric complexes, as is the case for K5 and K14, exhibit different dynamics. This suggests that individual polypeptides or homopolymeric complexes rather than exclusively heterodimeric/ tetrameric subunits, as is currently thought, can also take part in keratin intermediate filament assembly and dynamics. Biochemical analysis performed in the absence of protein synthesis revealed greater amounts of K5 than of K14 in the soluble pool of BMGE+H cells. Crosslinking and immunoprecipitation experiments indicated an excess of monomeric K5, as well as of K5/K14 heterodimers and K5 homodimers in the soluble pool. These results are in agreement with the different dynamic behaviour of these keratins observed in immunofluorescence. On the contrary, the phosphorylation levels of K5 and K14 are similar in both the soluble pool and the polymerized fraction, suggesting that phosphorylation does not play an important role in the different dynamics displayed by these two proteins. In summary, our results demonstrate that, following fusion, the keratin intermediate filament network reshapes rather rapidly and that keratins are highly dynamic proteins, although this mobility depends on each particular polypeptide

Automated control system for HgI2 crystals growth

We describe the control system developed for the automated growth of HgI2 crystals, mainly used for X and gamma radiation detectors. The system includes instrumentation for the precise measurement of the growth furnace temperatures and for their control, both needed to fulfill the strict requirements of the vapour phase crystal growth. A video camera and a VME grabber module allow the detection of the crystal nucleation and pattern recognition. This image analysis is used as input for the control actions. A VME based computer (MVM147SA-1 from Motorola) running a real time OS9 operating system performs: data collection, instrumentation programming, image acquisition, data analysis and control of the whole system making use of a highly structured software. The image analysis is done by means of a perceptron neural net classifier using a parameter invariant representation of the objects detected in the segmented images

Inhibition of pRb phosphorylation and cell-cycle progression by a 20-residue peptide derived from p16CDKN2/INK4A

Background: The CDKN2/INK4A tumour suppressor gene is deleted or mutated in a large number of human cancers. Overexpression of its product, p16, has been shown to block the transition through the G1/S phase of the cell cycle in a pRb-dependent fashion by inhibiting the cyclin D-dependent kinases cdk4 and cdk6. Reconstitution of p16 function in transformed cells is therefore an attractive target for anti-cancer drug design. Results: We have identified a 20-residue synthetic peptide--corresponding to amino acids 84-103 of p16--that interacts with cdk4 and cdk6, and inhibits the in vitro phosphorylation of pRb mediated by cdk4-cyclin D1. The amino-acid residues of p16 important for its interaction with cdk4 and cdk6 and for the inhibition of pRb phosphorylation were defined by an alanine substitution series of peptides. In normal proliferating human HaCaT cells and in cells released from serum starvation, entry into S phase was blocked by the p16-derived peptide when it was coupled to a small peptide carrier molecule and applied directly to the tissue culture medium. This cell-cycle block was associated with an inhibition of pRb phosphorylation in vivo. Conclusions: These results demonstrate that a p16-derived peptide can mediate three of the known functions of p16: firstly, it interacts with cdk4 and cdk6; secondly, it inhibits pRb phosphorylation in vitro and in vivo; and thirdly, it blocks entry into S phase. The fact that one small synthetic peptide can enter the cells directly from the tissue culture medium to inhibit pRb phosphorylation and block cell-cycle progression makes this an attractive approach for future peptidometic drug design. Our results suggest a novel and exciting means by which the function of the p16 suppressor gene can be restored in human tumours

Design of a modified uniform redundant-array mask for portable gamma cameras

Uniform redundant-array masks have been reported as good lenses to form the image of gamma sources, with the correlation between the mask-aperture matrix and the shadows projected on a static position-sensitive detector. We present a modified uniform redundant-array configuration suitable for portable and small-size y cameras; its ability to reconstruct the image of several sources is analyzed. We have carried out a Montecarlo simulation of the gamma interactions in the mask, defining the expected response of the correlation process and comparing it with that achieved with the usual uniform redundant-array configuration