Reducing control noise in gravitational wave detectors with interferometric local damping of suspended optics.

Control noise is a limiting factor in the low-frequency performance of the Advanced Laser Interferometer Gravitational-Wave Observatory (LIGO). In this paper, we model the effects of using new sensors called Homodyne Quadrature Interferometers (HoQIs) to control the suspension resonances. We show that if we were to use HoQIs, instead of the standard shadow sensors, we could suppress resonance peaks up to tenfold more while simultaneously reducing the noise injected by the damping system. Through a cascade of effects, this will reduce the resonant cross-coupling of the suspensions, allow for improved stability for feed-forward control, and result in improved sensitivity of the detectors in the 10-20 Hz band. This analysis shows that improved local sensors, such as HoQIs, should be used in current and future detectors to improve low-frequency performance.

Sensors and actuators for the advanced LIGO A+ upgrade.

Advanced Laser Interferometer Gravitational-wave Observatory (LIGO A+) is a major upgrade to LIGO-the Laser Interferometer Gravitational-wave Observatory. For the A+ project, we have developed, produced, and characterized sensors and electronics to interrogate new optical suspensions designed to isolate optics from vibrations. The central element is a displacement sensor with an integrated electromagnetic actuator known as a BOSEM (Birmingham Optical Sensor and ElectroMagnetic actuator) and its readout and drive electronics required to integrate them into LIGO's control and data system. In this paper, we report on the improvements to the sensors and the testing procedures undertaken to meet the enhanced performance requirements set out by the A+ upgrade to the detectors. The best devices reach a noise level of 4.5 ×10-11m/Hz at a measurement frequency of 1 Hz, an improvement of 6.7 times over standard devices.

The effect of form and dimension on the management of the maxillary arch in unilateral cleft lip and palate conditions.

Over the past 28 years, a series of studies at the West Midlands Regional Plastic Unit has compared the maxillary arches at birth and 4 months of 30 normal children and two groups of children with unilateral cleft lip and palate, one of which had presurgical maxillary orthopaedic treatment and the other which did not. Other studies have compared the area of palatal mucosa at birth with the overall size of the arch at 5 years of age and have also assessed the long term effect of simultaneous lip and palate repair and presurgical treatment on the profile, occlusion and speech of the older patient. The paper summarises the findings of the investigations and considers how they have contributed to an understanding of the unilateral cleft lip and palate problem particularly with regard to the long term management of such cases and the provision of a suitable treatment protocol.

An investigation to relate the overall size of the maxillary arch and the area of palatal mucosa in cleft lip and palate cases at birth to the overall size of the upper dental arch at five years of age.

The area of palatal mucosa and the size of the maxillary arches were measured in a group of 30 newborn infants with unilateral clefts of the lip and palate. The overall size of the maxillary arch together with the arch width and arch height were also measured when the children had reached 5 years of age. For comparison purposes, a group of 30 newborn normal children and 30 normal 5-year-old children were similarly measured. The cleft children were found to have a mean deficiency of palatal mucosa of 16.41% at birth, although the overall size of their maxillary arches was 17.08% greater than normal. In the cleft cases there was no significant correlation between the area of palatal mucosa at birth and the overall size of the arch at 5 years of age. A significant correlation did exist between the overall size of the arch at birth and the overall size when the child was 5 years old. The significance of this and other findings is discussed.

[Changes after presurgical orthopedic treatment in children with unilateral cleft lip and cleft palate]. / Veränderung nach prächirurgisch-orthopädischer Behandlung bei Kindern mit einseitiger Lippen-Kiefer-Gaumen-Spalte.

The study analyses the changes occurring in the maxillary arches of 30 infants with complete unilateral clefts of the lip and palate following presurgical maxillary orthopaedic treatment. 15 similar cases not receiving such treatment were used as controls together with 30 normal subjects. Photocopies of models of the arches at birth and 4 months were analyzed by computer and the area of palatel tissue measured using stereophotogrammetry. In the presurgical cases, the palatal cleft was significantly narrowed due to the transverse and antero-posterior dimensions of the arches increasing less than in the controls. The narrowing of the cleft was particularly marked in the alveolar region because the presurgical treatment minimised the antero-lateral (outward) rotation of the lesser segment which otherwise would have occurred. Somewhat surprisingly, the study showed that presurgical treatment tended to inhibit growth of palatal tissue and it was concluded therefore that the narrowing of the defect was due mainly to the growth pattern of the maxillary arch being modified by the appliances.

Presurgical changes in unilateral cleft palate subjects.

This investigation utilizes computerized measuring and statistical techniques, stereophotogrammetry, and a newly developed method of measuring palatal surface areas to study changes in the maxillary arch dimensions at birth and at 4 months in 3 groups of subjects: (1) 30 complete unilateral cleft lip and palate cases who were treated by presurgical maxillary orthopaedics; (2) 15 similar cases who had no such treatment and served as controls; and (3) 30 normal children. The changes occurring in the 3 groups over the 4-month period were compared. In particular, it was noted that presurgical treatment had a constrictive effect on general arch growth and that it also retarded the growth of palatal tissue. The significance of this in relation to other findings and to presurgical treatment in general is discussed.

A rapid method of measuring the palatal surface area of cleft palate infants.

A method is described for rapidly measuring the surface area of the palate by adapting a piece of soft plastic to a model of the upper jaw using a vacuum moulding technique. Tests with a hemisphere of known surface area showed the method to be consistent and to have a low degree of systematic error. When measuring models with unrepaired cleft palates, the error was found to be 2.1 per cent (compared with 3 per cent using stereophotogrammetry) but 7.1 percent when measuring intact palates. Because of the consistency of the method, the true palatal area could be calculated from the measured area by the use of a multiplying factor. These findings are described, and the application of the technique to the pretreatment assessment of cleft cases is illustrated by showing that, in a series of 30 cleft palate and 30 normal infants, a tissue deficiency of 16.8 per cent existed in the cleft subjects at birth.