Small Amount Of Rotation Research Articles

Rotational disturbance in laser-interferometric gravity gradiometry

Laser interferometers have been used for precise measurements of gravity and related effects. These include experiments to search for a fifth force and absolute ballistic gravimeters, which use a Michelson-type laser interferometer to measure the acceleration of a free-falling test mass. In these methods of instrumentation, the motion of free-falling test masses is measured using corner-cube laser interferometers, in which at least one retroreflector is embedded in each test mass. However carefully each of such test masses is released into free fall, a small amount of rotation is unavoidable which changes the optical path length and causes acceleration disturbance. This rotational disturbance could ultimately limit the measurement sensitivity of the laser interferometers. Various experimental and theoretical studies have been conducted to minimise the rotational disturbance in absolute ballistic gravimeters. This paper focuses on the rotational disturbance in laser-interferometric gravity gradiometers (LIGGs) that measure differential acceleration between two test masses freely falling at different heights in a vacuum. LIGGs can be configured to measure not only vertical gravity gradients, but also horizontal gradients, or gradients in both horizontal and vertical directions. However, only those to measure vertical gravity gradients have been constructed so far. Hence, in this paper, the term LIGGs specifically indicates the gravity gradiometers that measure vertical gravity gradients. Unlike absolute ballistic gravimeters, the LIGGs are, in principle, insensitive to ground vibrations; they can potentially detect some effects that are buried in seismic noise in absolute gravity data. To fully leverage this advantage of the LIGGs, it is crucial to keep the rotational disturbance to a minimum. Expressions for the rotational disturbance are derived and its magnitude is estimated based on available experimental data. The results show that the magnitude would not be more than 0.1 μGal /m in the measurement of vertical gravity gradients in a compact LIGG. Alternative designs and requirements for increasing the sensitivity of the LIGGs are also discussed.

Electron tomography of soot for validation of 2D image processing and observation of new structural features

Transmission electron microscopy of soot aggregates is performed using a tilting-stage with view angles from –60 to +50 degrees. The resulting series of images was used to produce videos and solid models to aid in the visualization of the structure. The images from 31 angles for each aggregate were analyzed using various 2D image processing techniques. It was found that the measurements of primary particle size varied by less than 16% as angles changed. Projected area measurements only varied by 6% as viewing angle changed. These variations are comparable to the errors expected from the image processing. Practically, 2D images are adequate for determining primary particle size and projected area with little noise or bias introduced by random projection angles. In addition, it was found that most of the aggregates contained closed ring structures, implying that during aggregation, a small amount of rotation at contact points occurs. This structural feature is not apparent in 2D images and suggests that tomography may be useful in studying soot formation and aging processes.Copyright © 2019 American Association for Aerosol Research

Arthro-Biomechanical Investigation of the Tarsal Joint of One-Humped Camel (Camelus dromedarius) during gait: Forensic Biomechanics Evidence

It is expected that dromedary camel’s tarsus plays a crucial role in survivals in the arid and semiarid regions. These regions are open and the dromedary camel is tall with long legs. Thus, databases of biomechanical variables are needed to investigate the changes of velocity, displacement, angular changes as well as anatomical consideration of tarsal joint during walking and stance phase. Nine healthy camels of three different sizes and ages were selected for gait analysis using motion track program. Moreover, five tarsal joints cadavers obtained for 3D reconstruction computed tomography. The present study stated that, tarsal joint is a hinge biaxial joint, primarily allowing flexion, extension and small amount of rotation and gliding movement. The gait analysis during walking revealed some data of hind limb velocity, angular change and displacement of tarsal joint. Different sizes of camel had no significant effect on average and minimum value of velocity of hind limb during walking. Medium sized camel showed higher degree of extension of tarsal joint than small and large one. Medium and large camel showed significant higher vertical (p=0.01) and horizontal (p=0.05) displacement of right tarsal joint than small camel during walking. We anticipate our findings can be a useful tool in lameness investigation to discriminate between the normal and diseased gait as expecting the nature of the inhabitant environment as well as add promising evidence in the field of forensic biomechanics to avoid legal violations in racing camels.

Oblique collision and accretion of the Netherlands Leeward Antilles to South America

Accretion of the Netherlands Leeward Antilles volcanic island arc to northern South America (offshore Venezuela) was accompanied by deformation and clockwise block rotation. Structural analysis of Aruba, Curaçao, and Bonaire indicates that they were deformed during at least one ductile event (D1) and three brittle events (F1 − F3). The first deformation phase (D1 and F1) began in the Early Cretaceous, at approximately 110 Ma. Deformation features are consistent with displacement partitioning at the obliquely convergent Caribbean‐Atlantic (proto‐Caribbean) plate boundary. This deformation was accompanied by an approximate 90° clockwise rotation of the forearc terrane. The onset of the second phase of deformation (F2) occurred in the Eocene (∼55 Ma), also accompanied by a small amount of rotation, and structures are consistent with wrench tectonics in a pull‐apart regime. This coincided with the collision of the Caribbean plate with the Great Bahama Bank and the initiation of convergence between North and South America. The youngest deformation structures and rotation (F3) are also associated with wrench faulting. Likely, motion along the Oca fault and the Caribbean plate transform fault initiated a major restraining bend in the late Paleogene. Beginning ∼12 Ma, the northeastward escape of the Maracaibo block further increased the complexity of tectonism at the Caribbean–South American plate boundary. Deformation structures are consistent with a total of 135° clockwise rotation of the Leeward Antilles islands and regional diachronous deformation from west to east since the Early Cretaceous.

下顎枝矢状分割術を施行した下顎前突症患者の正貌軟組織変化

The purpose of this study was to clarify soft tissue changes of a frontal face in prognathic patients following surgical mandibular retrusion.Twenty-two adult prognathic patients without facial asymmetry, who underwent sagittal splitting ramus osteotomy using screw fixation, formed the basis of this study. A pair of pre- and postoperative standardized frontal facial photos and lateral cephalograms were used for soft and hard tissue analysis. For quantitative evaluation of the facial photos, the amount of sagittal rotation of the head based on FH head position (0°) was computed using lateral cephalograms and the facial photos presenting less than ±2°of pitching angle of the head were used for the sample as proper frontal facial photos. A paired t test was used to indentify significant hard and soft tissue changes of a frontal face following surgery. A Pearson correlation analysis was used to distinguish soft tissue changes from hard tissue changes.The results were as follows:1.Skeletal deformity of the subjects was characterized by remarkable protrusion of the mandible, coupled with lingual tipping of the lower central incisors. Distinguishing mandibular backward movement with a small amount of rotation was found following surgery.2.Significant changes in the soft tissue were found in the shape and position of the lip. The thickness of the upper red lip significantly increased and the width of mouth aperture significantly decreased. The lip position demonstrated significant downward movement together with significantly increased height from subnasale to stomion and significantly decreased height from stomion to soft tissue menton.3.The facial width increased significantly at all areas and in particular, the ratio of facial width to lower facial height increased remarkably around the chin and lip areas.4.A significant correlation was found between the vertical positional change of lip and the sagittal change of the mandible, while no significant correlation was found between the change of lip shape and the sagittal change of the mandible.These results suggested significant effects of sagittal splitting ramus osteotomy on the change of lip shape and position as well as facial outline, which could remarkably improve the frontal facial appearance following surgery.

Heat Source in Infinite Plane with Elliptic Rigid Inclusion and Hole

The plane thermoelastic problems of a stationary heat source in an infinite plane with an elliptic rigid inclusion and an elliptic hole are analyzed under thermally adiabatic and isothermal boundary conditions. The problems of an elliptic rigid inclusion are derived for the following cases: (1) the case that there are rigid- body displacement and rotation; and (2) the case that there is no rigid-body displacement or rotation. To analyze these problems, the following three fundamental solutions are derived: Problem A, in which a point heat source exists within an infinite domain; Problem B, in which the inclusion has a small amount of rotation; and Problem C, in which the inclusion is subjected to concentrated loads. Two cases can be obtained by superimposing these fundamental solutions. For the hole problem, the fundamental solution (Green's function) is also derived. In analysis, the complex stress functions, the mapping function, and the thermal dislocation method are used. The complex stress functions are obtained as a closed form. For analytic examples, the stress distributions are shown under thermally adiabatic and isothermal boundary conditions. For the crack problem, the stress intensity factors are shown for the location of the heat source.

When did Sardinia stop rotating? New palaeomagnetic results

ABSTRACTPrevious palaeomagnetic results from Tertiary volcanic rocks of Sardinia suggest that the island underwent a quick counterclockwise rotation between 20.5 and 19 Ma. In order to test this hypothesis, a new palaeomagnetic study was carried out on sediments and volcanic rocks with well‐controlled biostratigraphic or radiometric ages younger than the suggested age for the end of the rotation.Unrotated palaeomagnetic directions obtained from the Upper Ignimbrites (radiometric age: 18.5–19.7 Myr) and the Aquitanian tuffs collected in the Anglona region (N Sardinia) would suggest that the rotation ended earlier than 20.5 Myr. The directions found in the volcanics are perhaps the result of secular variation, rather than differential rotation of the Anglona region with respect to surrounding regions.Two sites belonging to the upper ignimbritic unit (SI2) in the Monte Traessu‐Monte Rispisu area (Logudoro region) exhibited a large amount of rotation (D=320.4°, I=60°) which may be age related (radiometric age: 19.9 Myr). Four dikes (radiometric age: 18.3–16.7 Myr) in the Arcuentu volcanic complex (Arburese region) yield results (D=348.4°, I=33.8°) that indicate a further amount of rotation after their emplacement.Stable end‐point directions were successfully isolated from three Upper Burdigalian/Langhian sedimentary sites (biostratigraphic age: 18–15Ma) from the Marmilla and Logudoro regions. Consistent paleomagnetic directions obtained from these sites (D=352°, I=49°) indicate that a small amount of rotation was still to be completed in the Langhian time. This result is consistent with the history of Sardinian volcanism, which did not end until 13 Ma.

On the formation mechanisms for ellipticals and bulges

We study the formation of elliptical galaxies and the bulges of disk galaxies as a result of the collisionless collapse of a rotating star cloud. At small amounts of rotation, this process is accompanied by the bar mode of the radial orbit instability slightly modified by rotation. We refer this case to (giant) ellipticals. For moderate rotation, when the radial orbit instability is suppressed, another mode takes over, which is the direct continuation of a strongly damping mode at the limit of almost radial orbits; it turns into a practically non-damping and long-lived mode (for many revolutions), and even a slowly rotating bar may eventually be formed. It is natural to refer this case to bulges and dwarf elipticals. Then spirals could be formed from the clouds with large amounts of rotation.

Knee and Ankle Injuries in Children

The response of the skeletally immature child to musculoskeletal trauma is often quite different from the adult response to the same pattern of injury. The open growth plate is the primary factor accounting for this difference. The energy-absorbing capability of the growth plate is lower than that of bone, ligament, or tendon, which explains why the open growth plate is the preferential site for failure when a joint is injured. Because the growth plate will fail before these other structures, a true sprain of a child9s knee or ankle ligaments will be infrequent compared with the common nature of these injuries in adults. Injuries About the Knee Beware of the child with knee pain, and always consider the possibility of referred pain from the hip consequent to hip disorders of childhood or adolescence. Always fully examine the hip of a child who is complaining of knee pain. Also, examine the back to be certain the knee pain is not the result of pathology in the spine. ANATOMY The knee is a hinge joint that primarily permits flexion and extension. Small amounts of rotation are allowed but are carefully controlled by the ligamentous structures. Children usually exhibit greater ligamentous laxity than do adults. If laxity seems excessive in one knee, the opposite knee should be examined for comparison (ie, the control knee).

The effect of rotation on the hydrodynamics of stellar collapse

Using values of d, γmin, and γmax that Van Riper (1978) has found most promising for a hydrodynamic envelope ejection, we have shown that even a small amount of rotation in the initial core can stop its collapse before nuclear densities are reached. We expected χi > 0.02 to produce significant deviations from a spherically symmetric collapse, but have found that χi as much as ten times smaller than this will not allow the core to reach densities as high as in the spherical collapse. In no case, however, does the core flatten very much, nor does the value of β become very large. Low final β's preclude the formation of an axisymmetric torus. They also indicate that deformation of an iron core into a triaxial configuration or fragmentation of the core during its collapse is an extremely unlikely event. (Note: Classically, β must exceed 0.27 before a dynamic instability to non-axisymmetric perturbations is encountered.)

The Stability of Supermassive Stars

view Abstract Citations (157) References (32) Co-Reads Similar Papers Volume Content Graphics Metrics Export Citation NASA/ADS The Stability of Supermassive Stars Fowler, William A. Abstract The studies presented in this paper constitute an extension of previous work on relaxation oscillations in supermassive stars. It is shown that a relatively small amount of rotation is sufficient to remove the general-relativistic instability which arises in such stars when rotation is absent. The post-Newtonian equations for the binding energy and for the frequency of the fundamental mode of radial oscillation are derived and the close connection between these two quantities is exhibited. The equatorial instability associated with contraction under rotation is investigated and the results used to estimate the limiting mass in which hydrogen burning can be effective as a source of energy during relaxation oscillations. This limit is found to be at least 108 Mo and perhaps as high as l0 Mo whereas, without rotation, the limit arising from general relativistic considerations is 106 Mo. Publication: The Astrophysical Journal Pub Date: April 1966 DOI: 10.1086/148594 Bibcode: 1966ApJ...144..180F full text sources ADS |

Diagnostic Inflation of The Knee Joint

THE roentgenogram is a diagnostic aid of great value in bone and joint diseases. It reveals and confirms such pathologic changes as clinical medicine is often unable to visualize. In the early years of roentgenographic experience, one was unable to make a diagnosis from X-ray evidence alone. As a result of careful observation and study, however, the radiologist is frequently able to diagnose lesions without the contribution of clinical evidence. With the refinement of instruments added to careful study, the possibilities of diagnosis have become boundless. There are still a large number of conditions where the X-ray findings are exceedingly limited, among which the knee joint figures very conspicuously. This limitation is not due to the fact that the roentgenogram does not reveal the existing pathology, but may be attributed to the lack of our own knowledge in X-ray interpretation of soft tissue changes. Clinical medicine helps to pave the way for X-ray interpretation, but without surgical aid confirming the actual presence of pathology, the existence even of gastric ulcer would not have been as well known as it is to-day. A sufficient number of knees have not been operated upon in obscure conditions to correlate the pathology with the X-ray findings. The hazy outlines and shadows, therefore, mean nothing. We are still unable to disclose, in a large percentage of cases, the presence of a torn cartilage; or to disclose or interpret with a great degree of accuracy the existence of changes in the synovial membranes. In this paper we will deal with derangements of the knee joint which, under ordinary circumstances, present negative findings in the roentgenogram. Soft tissue structures do not readily cast a shadow unless considerable change has taken place, or some medium is introduced into the tissues to outline these structures. Liquids injected into a joint for diagnostic purposes are too irritating, often leading to adhesions, and are absorbed too slowly. Gaseous substances are preferable and therefore oxygen and carbon dioxide should be employed. Carbon dioxide has been used in our series of cases because it is very readily absorbed, producing very little irritation. One must be familiar with the pathology which takes place as a result of internal derangements of the knee and determine if the roentgenogram reveals these changes. The knee joint differs from all other joints in the body in that it is purely a hinge joint, permitting only a small amount of rotation, and that only when the knee assumes the position midway between flexion and extension. This position is often called the “danger zone,” because, when the joint is in this position, injuries take place which are of more serious consequence, namely, displacements and tears of the semilunar cartilages. The anatomical structures which as a rule show no changes in the roentgenogram are the synovial membrane, fat pad and the semilunar cartilages.