Delicate Objects Research Articles

Electrical probing for dimensional micro metrology

Each dimensional measurement is based on probed points on the surface of the measured object. However, the well-established tactile and optical probing techniques face limitations when small and delicate objects with complex shape have to be measured. With tactile measurements there is always the danger of damaging the workpiece by the probing force and the measurable point rate is quite low. With optical probing there is a principal resolution limit and accessibility to complex surfaces is hindered by the limited acceptable surface slope. Also undercuts are not measurable. To overcome these limitations a probing system based on an electrical probing interaction with a direct current of a few nanoamperes has been developed, tested and compared with traditional technologies. With this probing system coordinate measurements of micro parts as well as nanometer resolved surface topography measurements are feasible. By applying a wide range of probes accessibility problems can be drastically reduced compared to tactile or optical micro probing systems.

Modified temporal-phase-unwrapping method for measuring in real time the out-of-plane displacements of the tympanic membrane of Mongolian Gerbil

A technique for measuring in real-time continuous out-of-plane displacements of delicate objects is proposed, and demonstrated on the tympanic membrane of Mongolian Gerbil. The technique is based on the combination of two methods: the spatial phase shifting (SPS) and the modified temporal phase unwrapping (TPU). The combination allows to obtain, in several steps, the phase values of the points that undergo out-of-plane displacement as the object is deformed. The technique reduces the frame acquisition time of the standard TPU used in moiré interferometry by a factor of 4, which is important to diminish post-mortem artifacts during in-vitro experiments and to reduce motion artifacts in in-vivo tests. The proposed technique is robust against problems associated with the temporal phase-shifting method, such as nonlinear phase shift and noise. The advantages and disadvantages are discussed.

Collaborative approaches to designing effective digital image databases for the study of three‐dimensional museum collections

PurposeThis technical paper aims to define the steps necessary to create an effective two‐dimensional image databases representing three‐dimensional museum objects for the purpose of instruction.Design/methodology/approachThe participating institutions reviewed six key types of services: finding content, collecting content, accessing content, documentation, accessibility, and access control. The project created, converted, described and transferred digitized images and data records from each partner to the web where they became universally accessible through a single common search interface.FindingsThe paper finds that collaboration between different institutions creates rich collections, and relationships that benefit the community.Research limitations/implicationsCapturing elements of three‐dimensional objects in a traditionally two‐dimensional medium provides unique challenges for web delivery.Practical implicationsProvides learning materials and access to objects that were once locked in storage and rarely exhibited, especially fragile and delicate objects. Also provides an environment for students to learn how to work professionally they would not acquire in the classroom.Originality/valueNew techniques in digitization were used and experimented with that are not widely used with these type of collections.

Modeling and Design of a Piezoelectric Forceps Actuator for Meso∕Micro Grasping

Meso∕micro grasping of tiny soft objects such as biological tissues, which ranges from hundreds to thousands of micro-millimeters in dimension, plays a significant role in the fields of tele-surgery, minimally invasive surgery (MIS), and biomedical instrumentation. Recently, the authors proposed a novel piezoelectric forceps actuator (PFA), which is capable of grasping delicate soft objects. One of the advantages of the PFA over conventional MIS forceps lies in that it can be remotely controlled to achieve precision deflection and grasping force. Furthermore, it does not have any moving parts such as gears and hinges, and hence avoids problems in operation like friction, backlash, lubrication, leakage, and sterilization. In this paper, a mathematical model of the PFA is derived, based on which genetic algorithm (GA) is applied to optimize the grasping force-deflection relationship of the actuator. The model developed is experimentally verified on a prototype of the PFA.

The Aztec Feather Shield in Vienna: Problems of Conservation

The 450 year old feather shield “Ahuizotl” , formerly kept as part of the Collections of Ambras Castle, is not only one of the most significant, but also one of the most delicate objects of the Museum of Ethnology in Vienna. In terms of conservation related issues, it is one of the most challenging objects. The shield is made from different types of feathers (blue cotinga, scarlet macaw, yellow oriole and rose roseate spoonbill) which are arranged in rows. It is also made from several sheets of gold. The feathers have become very thin, whereas the gold sheets are very fragile by their very nature. Their supporting element is made from the inner bark of an agave tree which has been braided. It is stretched onto a ring of rattan and reinforced with wooden sticks. On the back of the object there is a sheet and two handles made from raw hide. Due to these highly sensitive aspects of the object, every transportation of the object remains a serious challenge for the conservators of the museum. Those damages to the feathers which are caused by oxidation, chemical degradation, light, mechanical deformation and insect attack are usually very obvious. But certain stages of these damages can only be detected on a very microscopic level, e.g. at the little hooks of the feathers which are responsible for holding the vane together.Therefore, even the smallest move or vibration will cause irreversible damage or loss. The main focus for the conservator will therefore be the prevention of any harmful effects on the object.Since its new installation into the gallery “Classical Antiquity of the New World” in 1992, the ceremonial feather shield “Ahuizotl” has been presented in a display case made by the company “Swarovski”. The display case is dust-proof and secured with an alarm. It is equipped with an anti-glare lighting system which operates via fibre glass technique and indirect lighting. The light source (halogen illuminant with variable illumination) is situated in the base of the display case. A fibre optical system channels the light into the display case without the radiation of heat or UV. The illuminance is 50 lux. By inserting Art Sorb Pearls as a buffer for the humidity, the relative humidity in the display case remains as balanced as possible and stays within justifiable limits. Any transportation of feather objects requires highest caution. For the loan of the “Ahuizotl” feather shield to the Royal Academy of Arts in London on occasion of the exhibition “The Aztecs” (November 16th-April 11th 2003), a special travelling box was designed in cooperation with the company “hs art service austria ” In this travelling box, the object rests on a base of two very light panels. These panels are made from polyurethane-foam which is pressed in-between two sheets of acid-free paper (KAPA-panels). The object is fixed to a silicone covered screen which is mounted in-between the panels.To mount the object onto the screen, the panel-screen unit can be vertically stuck into the travelling box. With the help of different space bars, the panel unit is fixed into the travelling box. As a result, no packing material will touch the object. Additionally, the light-weight travelling box will be surrounded by a shook-proof, heavy-weight climate box.

Room-temperature atmospheric pressure plasma plume for biomedical applications

As low-temperature nonequilibrium plasmas come to play an increasing role in biomedical applications, reliable and user-friendly sources need to be developed. These plasma sources have to meet stringent requirements such as low temperature (at or near room temperature), no risk of arcing, operation at atmospheric pressure, preferably hand-held operation, low concentration of ozone generation, etc. In this letter, we present a device that meets exactly such requirements. This device is capable of generating a cold plasma plume several centimeters in length. It exhibits low power requirements as shown by its current-voltage characteristics. Using helium as a carrier gas, very little ozone is generated and the gas temperature, as measured by emission spectroscopy, remains at room temperature even after hours of operations. The plasma plume can be touched by bare hands and can be directed manually by a user to come in contact with delicate objects and materials including skin and dental gum without causing any heating or painful sensation.

Active Acceleration Compensation for Transport Vehicles Carrying Delicate Objects

The goal of this research is to enhance the capabilities of transport vehicles so that they can carry delicate objects without extensive packaging. The proposed approach, as first described by Graf and Dillmann (1997), is to add a robotic device (e.g., a parallel manipulator) on top of the vehicle, the motion of which compensates for certain forces and moments. This approach is called active acceleration compensation. This paper discusses performance measures for the effectiveness of acceleration compensation and a new motion planning scheme, the augmented pendulum algorithm, that is particularly effective. The basic idea is to emulate the motion of a free-swinging pendulum to minimize lateral forces acting on the objects.

High-speed conveyor junction based on an air-jet floatation technique

This paper investigates how forces developed by air-jets might be used to convey or manipulate delicate planar objects at high-speed without damage. The theory of turbulent jets and classic fluid mechanics are used in combination with practical experiments to establish how air-jet velocities and forces are related to orifice size and supply pressure. The basic stability problem of how to support a planar object on a single or multiple-array of air-jets is discussed. A passive control solution is developed based on the insertion of a porous layer between the object and the air-jets. This solution is incorporated in a mechatronic conveyor junction that can selectively re-direct or lane rigid or flexible planar objects from one conveyor to another mounted at right angles. In trials the conveyor junction reliably handled fragile biscuits at more than eight per second and could re-direct objects travelling at up to 2.5 m/s.

Study of inks on paper engravings using portable EDXRF spectrometry

The prints are fragile and delicate art objects that need for its examination a suitable technique for “in situ”, non-destructive and rapid analyses. The energy dispersive X-ray Fluorescence (EDXRF) spectrometry with portable instrumentation offers these analytical properties. In this work we present the EDXRF analyses of eight engravings elaborated with different techniques (etching and heliogravure) from the 17th to 20th centuries. The characterization of the paper is directly done from its EDXRF spectra, whereas the inks are characterized by the ink plus paper analysis after subtracting the background from the paper spectrum. Inorganic components of the paper engravings and inks have been identified from the EDXRF spectra and the results are discussed. Also, we present EDXRF analyses for the identification of inorganic components from six samples of modern inks.

Fuzzy logic grasp control using tactile sensors

This paper presents a method to control a two-fingers gripper for safe grasping of fragile and delicate objects like glass, fruits or vegetables. The proposed control algorithm adjusts the motion of the fingers of a gripper using tactile feedback, so that an object is grasped with the minimal required force without the measurement of this force. The rules set of the control law is derived empirically by investigation of the human finger skills. The formulation of these rules and the inference mechanism are based on fuzzy logic. The controller receives the object velocity and acceleration and the detection of incipient slippage and adjusts the fingers motion. The main advantage of this method is that the designed controller is quite robust because knowledge concerning the size, the weight or the surface texture of the grasped object is not required. The object is stably grasped by applying a relatively low grasping force. Simulated experiments are presented to demonstrate the efficiency of the introduced fuzzy controller of robot grippers, while its performance is compared with a PID controller.

Human brain activity in the control of fine static precision grip forces: an fMRI study.

Dexterous manipulation of delicate objects requires exquisite control of fingertip forces. We have used functional magnetic resonance imaging to identify brain regions involved in the skillful scaling of these forces when normal human subjects (n = 8) held with precision grip a small object (weight 200 g) in the dominant right hand. In one condition, they used their normal, automatically scaled grip force. The object was held gently in a second condition; the isometric grip force was maintained just above the critical level at which the object would have slipped. In a third condition, the force was increased to hold the object with a more firm grip. The supplementary and cingulate motor areas were significantly more active during the gentle force condition than during either of the other conditions in all subjects, despite weaker contractions of the hand muscles. In addition, the left primary sensorimotor cortex, the ventral premotor cortex and the left posterior parietal cortex were more strongly activated during gentle than during normal grasping. These novel results suggest that these regions are specifically involved in dexterous scaling of fingertip forces during object manipulation.

Investigation of objects d'art by PIXE with 68 MeV protons

PIXE with 68 MeV protons has been developed to investigate the elementary composition of samples, that are up to several millimeters thick, in particular for objects d'art. The small energy loss of the beam allows to handle and position large and delicate objects conveniently in air. The cross-section for producing K and L X-rays is around 100 times higher for 68 than for 3 MeV protons, while the specific energy loss and therefore radiation damage is 10 times less; the radiation damage per emitted characteristic X-ray is consequently 1/1000. The beam can be focussed to 0.5 mm diameter, the typical measuring time is 200 s at 1 pA beam current. Nuclear reactions cause a background of γ-rays but do not noticeably activate the samples. The present set-up is sensitive to all elements heavier than sulfur, it is unrivalled for detecting all heavy elements in a depth of millimeters. The different absorption of the various K and L lines indicates the depth of the element in the sample. Systematic studies on realistic test samples, that simulate ancient paintings, and on glasses, ceramics and metallic objects have demonstrated the possibilities of the method.

PARTICLE PRODUCTION IN DE SITTER SPACE–TIME

The definition of vacuum in curved space–time is a delicate object. With Minkowski-like vacuum definition, the current has a characteristic behavior in Robertson–Walker space–time. In this work we study the behavior of Dirac current in a de Sitter space–time. The rapid oscillations of current is observed with respect to time and indicate vigorous instability in initial vacuum and is interpreted as vigorous particle production.

Persistent Precessing Texture-Trapped Domains in Low Temperature Superfluid 3 He

It has recently been discovered that at temperatures below about 0.2T C in superfluid 3 He-B, pulsed NMR excitation can generate a new coherently precessing spin state which can have a lifetime of tens of seconds. The free induction decay signal from this state has been called the persistent induction signal (PIS). The earlier observations of the PIS have found it to be highly irreproducible indicating a strong connection with the magnetic texture. Here we describe measurements of the PIS within an experimental cell which was designed to fix the textural configuration of the superfluid. The resulting PIS signals are now far more reproducible allowing a more systematic study of the behaviour which we present here. Furthermore in the latest cell the decay of this signal has been observed to last for up to 4 minutes at the lowest temperatures. While the precessing state is readily accessible to observation, at these temperatures it is a very delicate object and we can immediately see the influence of background radiation on the time evolution of the decay.

A Portable Microwave System for Woodworm Disinfestation of Artistic Painted Boards

Microwave power can be effectively used for disinfesting wooden objects of woodworms. Disinfestation is achieved by heating woodworms inside wood above their lethal temperature values.A prototype of a portable microwave system suitable for treating small and delicate wooden objects is described. The system, working at 2.45 GHz, used a commercial magnetron, a radiative applicator, and a non-contacting thermometer to monitor the temperature of the painted surface. A flow of air is blown through the applicator to cool the irradiated surface. A treatment bench has been set up to heat painted boards in controlled conditions. The applicator is placed on the rear side of the board, while the painted side is monitored by means of an infrared the to maintain its temperature below safe levels (e.g. 50–55 °C).Results concerning the effect of microwave heating on several specimens infested by woodworms in all metamorphical stages (egg, pupa and larva) are reported and discussed. Preliminary results about possible detrimental effects induced by heating on wooden boards and on painted surfaces are also reported.An experimental procedure for determining the SAR distribution produced by the applicator of the disinfestation system on a wooden board is described. The procedure is based on a the rmographic analysis of the heated object. An analysis of the SAR uncertainty due to thermal diffusion and to surface radiation and convection losses is carried out, showing advantages and limitations of the thermographic method.

Two Housings: Modifying a Standard Box and Constructing an Oversize Sink Mat

Two housing solutions were devised by the author: one for unique and delicate art objects made from brittle, dried leaves and another for a group of 12 large maps. The housing designed for the “leaf portraits” uses a standard print box and a deep double sink with a friction mount as a base to secure and protect the leaves. The map housing is an oversize sink mat made of Coroplast polyflute and Fomecor. Difficulties with adhesion to the Coroplast are briefly discussed, and a detailed construction outline is given.

Two Housings: Modifying a Standard Box and Constructing an Oversize Sink Mat

Two housing solutions were devised by the author: one for unique and delicate art objects made from brittle, dried leaves and another for a group of 12 large maps. The housing designed for the “leaf portraits” uses a standard print box and a deep double sink with a friction mount as a base to secure and protect the leaves. The map housing is an oversize sink mat made of Coroplast polyflute and Fomecor. Difficulties with adhesion to the Coroplast are briefly discussed, and a detailed construction outline is given.

Deformation mapping and surface inspection of historical monuments

Electronic speckle pattern interferometry (EPSI) in various configurations (reference beam or shear) as well as double exposure speckle photography are applied for deformation monitoring in historical monuments. On-the-site measurements are made possible by a rigid construction of the optical head, common path configurations and portable image processing equipment. The delicate objects particularly call for non-intrusive measurement. Basic features of the techniques, their implementation and results from historical sites are presented. Inhomogeneities in plaster, paint or natural stones were detected and related to crack formation. The reversibility of deformations under mechanical load was checked. In frescos, debonds from the carrier wall could be discovered and the detrimental effects of crystalline efflorescences were studied. Correlation analysis in ESPI images showed the influence of moisture on a rough stone surface and exposed microbiological activity. Thus, valuable deformation data could be obtained that assist in the diagnostics of deterioration processes and provide information in the design of remedies.

Archaeological applications of PIXE and IXX for paperlike objects at Fudan University

The PIXE and IXX analyses of paperlike museum objects at Fudan University are summarized. Emphasis is laid on preventing the samples from being damaged by irradiation. An on-demand beam pulsing system is useful for the PIXE analysis of delicate objects. IXX is more suitable in terms of damage compared to PIXE. Some PIXE and IXX applications of archaeological paperlike samples are given.

C07 Short and long term regulation of adenosine transport

Mechanical and electrical properties of Ketjenblack/silicone–rubber porous composites having 68–81% porosity were investigated. The porous composites had 1–6% compressive elastic moduli of composites having the same integrant without pores. The resistivity of the porous composite, under compression, monotonously decreased in a wide strain range (0–80%), while in a narrow range (0–10%) in the case of the composites without pores. Moreover, under cyclic compression, resistivity hysteresis was smaller in the case of porous composites compared to the case of composites without pores. These facts show that the porous composites are promising tactile sensor materials applicable to delicate or brittle objects.