Behaving badly? The conservation of modern textile art

Textile conservators are increasingly likely to be asked to treat modern textile artworks. These often present new challenges: they may be made of unusual materials whose deterioration patterns are unfamiliar, they may utilise traditional textile techniques in unusual ways. Modern artworks may be hung in unconventional ways, or be displayed in spaces which are not standard museum venues. It is commonly accepted that it is necessary to gain as much information as possible in order to preserve the artist’s intent when treating modern artworks. Legislation also gives the artist moral rights over his or her work. The issues involved in the conservation of modern textile artworks are illustrated with examples of pieces treated at the Textile Conservation Centre, UK, among others, and with particular reference to a piece by Robert Rauschenberg

Linear Stability Analysis of Symmetric Periodic Simultaneous Binary Collision Orbits in the Planar Pairwise Symmetric Four-Body Problem

We apply the symmetry reduction method of Roberts to numerically analyze the linear stability of a one-parameter family of symmetric periodic orbits with regularizable simultaneous binary collisions in the planar pairwise symmetric four-body problem with a mass $m\in(0,1]$ as the parameter. This reduces the linear stability analysis to the computation of two eigenvalues of a $3\times 3$ matrix for each $m\in(0,1]$ obtained from numerical integration of the linearized regularized equations along only the first one-eighth of each regularized periodic orbit. The results are that the family of symmetric periodic orbits with regularizable simultaneous binary collisions changes its linear stability type several times as $m$ varies over $(0,1]$, with linear instability for $m$ close or equal to 0.01, and linear stability for $m$ close or equal to 1.Comment: 13 pages, 1 figur

Blue flag with yellow tiger? Flags, authenticity and identity

The Flag of the Formosa Republic in the collection of the National Taiwan Museum is a national icon. It is a copy of one made in 1895 to mark the formation of a new Taiwanese republic; this replica, described in a contemporary newspaper account as an exact copy, was made in Japan in 1909. The painted flag was an intriguing puzzle. Instrumental analysis and a close study of the flag itself and of surviving historic photographs and records were used to try to establish whether what looked like later additions and repairs were actually part of the original construction. An international team of conservators and scientists from Taiwan, the UK, the USA and Germany carried out the investigation and the conservation treatment. Although dye analysis was inconclusive and it has not yet been possible to ascertain the original colour, it was felt that an addition in the upper right corner and some of the repairs could well be part of the original construction and these were left in situ though other repairs were removed. The paper lining was removed, revealing that the flag was painted on both sides. The fabric was cleaned using a vacuum suction table, while the paint surface was cleaned with swabs. The flag was supported using an adhesive treatment with Lascaux acrylic resin

The measurement of small ionic currents in living organisms by means of sensitive magnetometry

Recent research on developing and healing tissues suggests that small quasl-d. c Ionic currents (of magnitude 10-20/iA) may play a controlling role In the Initiation and organisation of growing tissues, but the difficulties of measuring such small currents has led to confusing results. Sensitive magnetometry provides a method of demonstrating, and, to some extent, locating such currents. A novel SQUID magnetometer system has been built and used to Investigate the magnetic fields around the uninjured human leg, and the developing chick embryo In ovo. Analysis of the magnetic fields around the human leg reveals the presence of macroscopic current loops (of magnitude up to 12/iA) within the leg. These currents are broadly similar In all subjects, and show day-to-day reproducibility In Individuals. They change predictably with time of muscle relaxation, and revert to the original signal on muscular exertion. These currents are of significance when considering the therapeutic use of Injected current for the healing of non-union in bone. The magnetic fields around eggs are detectable from day two of Incubation, and Increase In magnitude until day four or five, by which time there Is a magnetic field pattern with a null line over or near the centre of the egg. After day five the magnetic field Is reduced In size and of more complex pattern. The magnetic fields disappear If the egg Is cooled, and reappear on rewarmlng. Mathematical analysis suggests that the magnetic fields have a source deeper within the egg than the embryo Itself, probably the extra- embryonic membranes

Progress in strain monitoring of tapestries

This paper reports interdisciplinary research between conservators and engineers designed to enhance the long-term conservation of tapestries (tapestry-weave hangings) on longterm display. The aim is to monitor, measure and document the strain experienced by different areas of a tapestry while it is hanging on display. Initial research has established that damage can be identified in the early stages of its inception, i.e., before it is visible to the naked eye. The paper also reports initial results of strain data visualisation that allows curators and conservators to examine how strain develops, thereby facilitating predictions about the changes in the form or condition of the tapestry. Strain data visualisation also allows the strain process to be recorded, thereby facilitating the effective documentation of display methods and conservation interventions. The paper reports the use of point measurements (using silica optical fibre sensors) and full-field monitoring (using 3-D photogrammetry with digital image correlation (DIC))

Relative Equilibria and Periodic Orbits in a Binary Asteroid Model

We present a planar four-body model, called the Binary Asteroid Problem, for the motion of two asteroids (having small but positive masses) moving under the gravitational attraction of each other, and under the gravitational attraction of two primaries (with masses much larger than the two asteroids) moving in uniform circular motion about their center of mass. We show the Binary Asteroid Model has (at least) 6 relative equilibria and (at least) 10 one-parameter families of periodic orbits, two of which are of Hill-type. The existence of six relative equilibria and 8 one-parameter families of periodic orbits is obtained by a reduction of the Binary Asteroid Problem in which the primaries have equal mass, the asteroids have equal mass, and the positions of the asteroids are symmetric with respect to the origin. The remaining two one-parameter families of periodic orbits, which are of comet-type, are obtained directly in the Binary Asteroid Problem.Comment: 34 page, 8 figure

Strain monitoring of tapestries: results of a three-year research project

The outcomes of an interdisciplinary research project between conservators and engineers investigating the strain experienced by different areas of a tapestry are described. Two techniques were used: full-field monitoring using digital image correlation (DIC) and point measurements using optical fibre sensors. Results showed that it is possible to quantify the global strain across a discrete area of a tapestry using DIC; optical fibre and other sensors were used to validate the DIC. Strain maps created by the DIC depict areas of high and low strain and can be overlaid on images of the tapestry, creating a useful visual tool for conservators, custodians and the general public. DIC identifies areas of high strain not obvious to the naked eye. The equipment can be used in situ in a historic house. In addition the work demonstrated the close relationship between relative humidity and strain

Ocular orientation during head and eye movements : an evaluation with a three dimensional scleral induction coil technique

This thesis presents the results of oculomotor recordings obtained with a new type of scleral induction coil with which horizontal, vertical and torsional eye movements were measured simultaneously. In Chapter II, the stability of gaze in these three dimensions was measured in eight emmetropic observers. Subjects held the head still or oscillated it at 0.16~0.67 Hz (amplitude about 10 deg) in the horizontal, vertical or torsional plane while fixating a point target at optical infinity. Veridical gaze and head coordinates were calculated with full correction for non-linear goniometric relations and for cross-coupling artifacts due to misalignments of the coil on the eye. The amount of gaze instability in the horizontal and vertical direction was virtually identical. With the head still, in either of these directions the mean standard deviation of gaze position (inclusive saccades) was about 7 min arc; mean non-saccadic retinal image speeds were 20-30 min arcjsec. During head oscillation these values increased to about 16 min arc and 1 deg/sec; a mean of about 2.5% of the head motion remained uncorrected by the compensatory eye movements. Gaze stability in the torsional plane was considerably inferior to that in the horizontal and vertical plane. With the head held still, the mean S.D. position was about 17 min arc; (short-term drift) of torsional gaze mean torsional non-saccadic retinal image speed was about 46 min arcjsec. Long-term drift, expressed as the S.D. of the mean of torsional gaze position in consecutive zero position measurements, was 2.14 deg. Gain of the torsional compensatory eye movements was frequency dependent and rose from about 0.26 in static conditions (0 HZ') tO~-:about 0.42 at 0.16 Hz and 0.64 at 0.67 Hz. The validity of Listing's law was reinvestigated in Chapter III by means of a direct test. Either eye of 4 subjects was measured monocularly. Eye positions were measured in Fick coordinates and ocular torsion values were compared to the theoretical ones predicted by Listing's law. During consecutive measurements in the primary position torsion values were close to zero although considerable fluctuations of torsion were seen. Short-term drift was about 8' min arc and long-term drift about 1.64 deg. Torsion values in the secondary positions were also close to zero. In the tertiary positions torsion in the direction as predicted by Listing's law and increasing with eccentricity was recorded. In the temporal quadrants mean torsion was quantitatively in agreement with Listing's law; torsion values in the nasal quadrants however showed systematically larger values and this discrepancy increased with eccentricity to more than 50%. Statistical support for this finding however, was seen only in 4 out of 8 eyes. Symmetry could be obtained by shifting the chosen horizontal primary position (gaze parallel to the midplane) in the temporal direction; as a consequence all measured torsion ·values would exceed the ones specified by Listing's law. Torsion values varied idiosyncratically among subjects and among the left and right eyes of any one subject. It is concluded that Listing's law specifies ocular torsion only approximately: physiological eye movements show considerable stochastical as well as systematical deviations from this law