Compensation for thermal effects in mirrors of Gravitational Wave Interferometers

In this paper we study several means of compensating for thermal lensing which, otherwise, should be a source of concern for future upgrades of interferometric detectors of gravitational waves. The methods we develop are based on the principle of heating the cold parts of the mirrors. We find that thermal compensation can help a lot but can not do miracles. It seems finally that the best strategy for future upgrades (``advanced configurations'') is maybe to use thermal compensation together with another substrate materials than Silica, for example Sapphire.Comment: 20 pages, 12 figure

Measurement of Thermo-Elastic Deformation of an Optic using a Polarization Based Shearing Interferometer

A shearing interferometer is presented which uses polarization control to shear the wavefront and to modulate the interference pattern. The shear is generated by spatial walk-off in a birefringent crystal. By adjusting the orientation of the birefringent crystal, the components of the wavefront gradient can be independently measured to allow determination of the full wavefront vector gradient as well as reconstruction of the wavefront. Further, the monolithic nature of the crystal used for shearing allows the interferometer to be setup without need for precise alignment of any components. An algorithm incorporating homodyne detection is presented which analyzes the modulated interferograms to determine the components of the wavefront gradient, from which the wavefront is reconstructed. The thermal deformation of a mirror subject to heating from absorption of a Gaussian pump beam was accurately observed with a sensitivity better than \lambda/160. We show that this sensitivity is scale invariant, and present a method to account for the non-uniform spatial frequency response of the interferometer

ACUTA eNews August 1991, Vol. 20, No. 8

In This Issue President\u27s column Business meeting Regional meetings User groups Director\u27s column Workshop in Atlant

Detection of gravitational wave bursts by interferometric detectors

We study in this paper some filters for the detection of burst-like signals in the data of interferometric gravitational-wave detectors. We present first two general (non-linear) filters with no {\it a priori} assumption on the waveforms to detect. A third filter, a peak correlator, is also introduced and permits to estimate the gain, when some prior information is known about the waveforms. We use the catalogue of supernova gravitational-wave signals built by Zwerger and M\"uller in order to have a benchmark of the performance of each filter and to compare to the performance of the optimal filter. The three filters could be a part of an on-line triggering in interferometric gravitational-wave detectors, specialised in the selection of burst events.Comment: 15 pages, 8 figure

Radiation Pressure Induced Instabilities in Laser Interferometric Detectors of Gravitational Waves

The large scale interferometric gravitational wave detectors consist of Fabry-Perot cavities operating at very high powers ranging from tens of kW to MW for next generations. The high powers may result in several nonlinear effects which would affect the performance of the detector. In this paper, we investigate the effects of radiation pressure, which tend to displace the mirrors from their resonant position resulting in the detuning of the cavity. We observe a remarkable effect, namely, that the freely hanging mirrors gain energy continuously and swing with increasing amplitude. It is found that the `time delay', that is, the time taken for the field to adjust to its instantaneous equilibrium value, when the mirrors are in motion, is responsible for this effect. This effect is likely to be important in the optimal operation of the full-scale interferometers such as VIRGO and LIGO.Comment: 27 pages, 11 figures, RevTex styl

PENERAPAN MODEL PEMBELAJARAN KOOPERATIF TIPE SNOWBALL THROWING DALAM PEMBELAJARAN IPS DI KELAS IV SD

Penelitian ini dilator belakang kurangnya motivasi peserta didik terhadap pembelajaran IPS karena bersifat Abstrak, terlalu banyak hafalan yang harusdiingat serta membutukan pemahaman yang holistik. Penenitian ini ditujukan pada penggunaan model pembelajaran kooperatif tipe Snowball Throwing untuk meningkatkan motivasi belajar siswa terhadap pembelajaran IPS. Metode yang digunakan adalah penelitian tindakan kelas (Class Room Action) yang dikembangkan oleh Kemmis dan Me Taggart, dilaksanakan dalam dua siklus dengan subyek penelitian siswa kelas 4B SDN (Y) kecamatan Suka Sari yang berjumlah 45 orang. Prosedur penelitian terdiri dari rencana(Planning), tindakan (action), pengamatan (observation), dan refleksi (reflection).Teknikpengumpulan data dilakukan dengan menggunakan hasil perkembangan aktivitas level kelompok dan perkembangan aktivitas level; kelas. Hasil yangdiperoleh dengan menggunakan model pembelajaran kooperatif tipe Snowball Throwingdapat meningkatkan aktivitas belajar siswa dalam pembelajaran IPS karena model pembelajaraninidikemasdalamsebuahpermainan yang menyengankan bagi siswa, namun tujuan pembelajaran ini dapat tercapai. Model pembelajaran kooperatif tipe Snowball throwing dapatdijadikan alternative pilihan untuk meningkatkan motivasi belajar siswa sekolah dasar pada materilainnya. ---------- This study dilatarbelakang lack of motivation of learners towards learning Abstract IPS because it is, too much rote to remember and membutukan holistic understanding. Penenitian is aimed at the use of cooperative learning model Snowball Throwing to increase students' motivation towards learning IPS. The method used is action research class (Class Room Action) developed by Kemmis and Me Taggart, conducted in two cycles with research subjects 4B grade students of SDN (Y) districts Suka Sari, amounting to 45 people. The procedure consisted of a plan (Planning), action (action), observations (observation), and reflection (reflection). Techniques of data collection is done by using the results of the development activity group level and the level of development activity; class. Results obtained by using cooperative learning model Throwing Snowball can improve students' learning activities in social studies learning because learning model is packaged in a game that menyengankan for students, but learning objectives can be achieved. Cooperative learning model Snowball throwing can be used as an alternative option to increase students' motivation primary schools in other materials

Pathogenic and Molecular Characteristics of Two Isolates of HEV-B Species

Enteroviruses (EVs) are small non-enveloped RNA viruses forming a large group of different serotypes. EVs belong to the family Picornaviridae. The primary replication site of an enterovirus is typically the epithelium of the respiratory tract and the gastrointestinal mucosa. Virus replication in the gastrointestinal mucosa may continue, often asymptomatically, for several weeks occasionally causing viremia. During the viremia the virus spreads through the lymphatic system and circulation. Organ-specific symptoms rise after viral replication in the secondary target tissues. Occasionally, cellular adaptation is required for a virus to initiate replication in the secondary target tissue(s). Adaptation is linked to mutation(s) which may lead to alteration in cellular tropism, e.g., recognition of new surface receptor molecules or other host cell constituents essential for virus entry and replication. However, the critical step may also occur later during in the interaction of the host cell and the replicating virus. In the present study, genetic changes responsible for altered phenotypic features were sought using two strains of Human enterovirus B (HEV-B) species. Firstly, a laboratory isolate of coxsackievirus B5 (CV-B5), strain DS, was passaged 15 times in mouse pancreas in vivo, which resulted in a diabetogenic mouse pancreas passaged virus strain (MPP). The concept of diabetogenic means the ability of the MPP strain to replicate, cause insulitis and dysregulation of the glucose metabolism in the mouse pancreas in vivo. The interaction between the MPP virus strain and insulin producing β-cells was further studied in cell culture using a mouse-derived insulinoma cell line, MIN-6 cells, as an experimental model. The replication of the MPP virus strain was clearly slower in the MIN-6 cells compared to the other tested cell lines. After three days of incubation, extensive replication of MPP was evident in MIN-6 cells and resulted in a MIN-6 cell-adapted virus strain (MCA). Secondly, the ability of the D207 virus strain, isolated from a type 1 diabetic patient, to replicate in a primary human β-cell culture was tested. D207 was initially serotyped as coxsackievirus A9 (CV-A9) in a virus-specific neutralization assay. The D207 virus strain was found to cause cytolysis in the primary human β-cells and, simultaneously, severe functional damage of the surviving β-cells. The genomes of the four virus strains DS, MPP, MCA and D207 were cloned and sequenced. The sequence comparison of three CV-B5 strains (DS, MPP, and MCA) revealed only limited changes, three capsid and two non-structural (NS) amino acid substitutions between MPP and DS, and two capsid and six NS amino acid substitutions between MCA and MPP. In order to determine which of the amino acid substitutions were responsible for the changed phenotype in vivo and in vitro, full-length infectious clones were constructed from the MPP virus and its parental DS virus. By using reverse mutagenesis and chimeric viruses (MPP/DS and DS/MPP), it was shown that a change from MPP to the MCA phenotype in MIN-6 cells was mediated by only a single amino acid at position 94 in VP1, while the in vivo adaptation of the DS virus strain to the inflammation-inducing MPP virus strain may require multiple genetic determinants in the virus capsid and probably also in the NS proteins. Sequence analyses of D207 revealed that the virus belonged to a genogroup D of E-11, but was also neutralized with monotypic antisera to CV-A9. The isolate D207 was found to be closely related to a specific E-11 strains known to cause uveitis. Uveitis-causing E-11 strains were also found to be well neutralized with both CV-A9- and E-11-specific antisera. In a further study, a wide range of E-11 isolates were included to test the observed dual neutralizibility among isolates belonging to the D genogroup. Five of the six studied strains belonging to genogroup D were also neutralized with antisera against coxsackievirus A9 Griggs. The peptide scanning technique was utilized to identify antigenic regions of the capsid proteins of the D207 strain responsible for the observed dual neutralization. Several regions in the capsid of D207 were found to cross-react with an antiserum raised against CV-A9. However, epitopes responsible for the cross-neutralization remained unidentified. In conclusion, these studies indicate that the specific location of mutation may affect the phenotype of an enterovirus more than the overall quantity of changes. In the experimental settings, radical changes in the viral phenotypic features occurred only after a few amino acid substitutions. The majority of the studied viruses in the genogroup D of E-11 maintained exceptional phenotypic property, the cross-neutralization with CV-A9 specific antiserum, despite their genetic divergence.Pikornaviruksiin kuuluvat ihmisen enterovirukset ovat pieniä, pyöreitä ja vaipattomia RNA-viruksia, joista tunnetaan suuri määrä erilaisia serotyyppejä. Enterovirusinfektiot alkavat yleensä hengitystien ja suoliston epiteelissä, jossa suurin osa viruksista kulkeutuu mahalaukun läpi suolistoon. Enterovirukset aiheuttavat pääasiallisesti systeemisiä yleisinfektioita, joiden oirekirjo määräytyy virusten toissijaisen lisääntymispaikan mukaan. Joskus enteroviruksen lisääntyminen toissijaisessa lisääntymispaikassa edellyttää sopeutumisprosessia. Sopeutuminen johtuu geneettisistä mutaatioista, jotka voivat johtaa uuden solunpintareseptorimolekyylin tai muun isäntäsolun molekyylin tunnistamiseen ja jotka ovat välttämättömiä virusten pääsylle soluun. On myös mahdollista, että sopeutumiselle kriittinen vaihe on myöhempi vuorovaikutus isäntäsolun ja lisääntyvän viruksen välillä. Tutkimuksen tarkoituksena oli tunnistaa fenotyyppisistä ominaisuuksista vastaavia virusgenomin osia kahdesta ihmisen enterovirus B -lajiin kuuluvasta viruksesta. Coxsackie B5 -viruskanta (DS) saatiin muuntumaan kasvattamalla sitä viisitoista kertaa hiiren haimassa in vivo. Muuntuneiden virusten joukosta löytyi ns. diabetogeeninen virus (diabetogeeninen CV-B, CV-B5-MPP), joka sai aikaan kroonisen tulehdusreaktion hiiren haimassa. Osalla hiiristä todettiin myös häiriötä sokerimetaboliassa. Seuraavaksi MPP-infektiota tutkittiin yksityiskohtaisemmin hiiren insulinomasolulinjassa (MIN-6). Tutkimuksessa havaittiin, että edellä kuvatun MPP-viruksen lisääntyminen on hyvin hidasta. Replikaatio kiihtyi vasta kolmen vuorokauden kuluttua. Tutkimuksessa tarkasteltiin myös tyypin 1 diabeetikolta (lapsi) eristetyn coxsackievirus A9:n (CV-A9) molekyyligeneettisiä ja biologisia ominaisuuksia. Kyseinen kanta (D207) oli eristetty Slovakiassa, jossa se tyypitettiin serologisin testein coxsackievirus A9:ksi. D207-kanta infektoi ihmisen primäärisiä insuliinia tuottavia β-soluja tehokkaasti aiheuttaen solutuhon sekä vakavan toiminnallisen häiriön eloonjääneissä β-soluissa. Neljän viruksen DS, MPP, MCA ja D207 genomit kloonattiin ja sekvensoitiin. Ensimmäisten kolmen viruksen sekvenssit analysoitiin ja havaittiin, että DS- ja MPP-kantojen välillä löytyi vain viisi aminohappoeroa, joista kolme sijaitsi kapsid- ja kaksi ei-rakenneproteiinissa. Vertailtaessa MPP- ja MCA-kantoja niissä havaittiin kahdeksan aminohappoeroa, joista kaksi kapsid- ja kuusi ei-rakenneproteiineissa. Kapsidialueelta löydettyjen aminohappomuutosten merkitys selvitettiin ns. kohdennetun mutageneesin avulla. Hiiren haimassa in vivo kasvatetun CV-B5-MPP-viruksen infektiivisen genomin mutaatiokohdat muutettiin yksitellen alkuperäiseen DS- tai MCA-viruskannan kaltaisiksi. Tutkimuksessa tehtiin myös kaksi rekombinanttivirusta liittämällä MPP:n viruskannan 5 -UTR-kapsidi-alue DS viruskannan ei-rakenneproteiinin 3 UTR-alueeseen ja vastaavasti päinvastoin (MPP/DS ja DS/MPP). Tulokset mutanteilla tehdyistä MIN-6-solujen infektiokokeista osoittivat selvästi, että kapsidiproteiinin VP1 aminohappo 94 (Ile) oli vastuussa viruksen lisääntymisestä insuliinia tuottavissa MIN-6-soluissa. Sen sijaan in vivo infektio oli monimutkaisempi ja vaati useampia aminohappomuutoksia kapsidissa ja todennäköisesti myös ei-rakenneproteiini-alueella. D207-viruksen sekvenssien analyysi muihin virussekvensseihin verrattuna osoitti, että D207 kuuluu echovirus 11:n (E-11) alaryhmään D. Tästä huolimatta viruksen havaittiin neutraloituvan hyvin CV-A9 spesifisellä neutraloivalla vasta-aineella. Kaksoisneutraloituvuus osoittautui olevan yhteinen ominaisuus suuremmalla osalla E-11-virusten D-alaryhmään kuuluvilla viruksilla. Jatkotutkimuksen tulokset osoittivat, että kaikki tutkitut kannat neutraloituivat odotetusti E-11:n prototyyppikannan Gregoryn antiseerumilla. Yllättävää oli se, että viisi kuudesta D-genoryhmään kuuluvasta viruskannasta neutraloitui myös CV-A9:n Griggs-prototyypin antiseerumilla. Tämä osoitti, että tutkituilla echoviruskannoilla oli yhteisiä antigeenisiä alueita CV-A9:n kanssa. Vaikka monia ristiinreagoivia antigeenisiä peptidejä on löydetty, tässä tutkimuksessa neutraloituvuudesta vastaavia epitooppeja ei yrityksistä huolimatta kyetty tunnistamaan. Nämä tutkimukset osoittivat, että mutaation sijainnilla on enemmän vaikutusta enteroviruksen fenotyyppiin kuin kokonaismutaatiomäärällä. Koejärjestelyissä vain muutamat aminohapposubstituutiot johtivat radikaaleihin muutoksiin virusfenotyypissä. Suuralla osalla E-11 D -alaryhmän viruksia oli poikkeuksellinen fenotyyppi omaisuus, ristiin neutraloituminen CV-A9 -spesifisellä antiseerumilla, vaikka virukset olivat geneettisesti hyvin erilaisia

The new « Hippocampe » OBS and the French OBS pool

The study of continental margins, subduction zones and oceanic basins as well as the quantitative assessment of seismic hazard near densely populated coastal areas request the deployment of a large number of Ocean Bottom Seismometers (OBS) during period of several weeks for active tomography, up to several months for passive experiment

Virgo and the quest for gravitational waves

In the past ten years,several giant interferometers have been built around the world with the goal ofa first direct detection ofgravitational waves.The most sensitive detectors,2 interferometers for the US LIGO collaboration and the detector built by the Italo-French collaboration Virgo (fig.1) are approaching their design sensitivity. Scientific exploitation ofthese instruments is now starting ..