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PubMed1995

Accessibility of a glucocorticoid response element in a nucleosome depends on its rotational positioning.

Gene expression requires binding of transcription factors to their cognate DNA response elements, the latter being often integrated into sequence-specifically positioned nucleosomes. To investigate the constraints imposed on factor-DNA recognition by the nucleosomal organization, we studied the binding of glucocorticoid receptor to a single glucocorticoid response element (GRE) displaying four different rotational frames in three different translational positions in reconstituted nucleosomes. We demonstrate that rotational setting of the GRE per se is important for its accessibility. Furthermore, the effects of rotational positioning of the GRE are different for different translational positions of the GRE in the nucleosome. A GRE placed near the nucleosomal dyad is totally blocked by rotating it 180 degrees so that the major groove of the GRE faces the histone octamer. If, on the other hand, the GRE is placed about 40 bp from the nucleosome dyad, then the 180 degrees rotation of the GRE still allows glucocorticoid receptor binding, albeit with a sixfold lower affinity than the peripherally oriented GRE. This suggests that both the rotational positioning and the translational positioning function as a framework for transcription factor response elements in gene regulation.

Base Sequence↗
PubMedDate not supplied

Educational instruction on a hospital information system for medical students during their surgical rotations.

OBJECTIVE: To evaluate the benefit, for medical students on their surgical rotations, of real-time educational instruction during order entry on a hospital information system. DESIGN: Prospective controlled trial. INTERVENTION: Access to educational information during computerized order entry. SUBJECTS: Medical students in their final year at the University of Calgary. MAIN OUTCOMES: Attainment of the surgery rotation educational objectives, as measured by performance on a multiple-choice examination. METHODS: Before they began their surgical rotations, students at two hospitals took a multiple-choice examination to measure their knowledge of surgery. One hospital had an information system with computerized order entry; students at this hospital had access, while composing orders, to educational material on the system. The other hospital did not have an information system; students there wrote orders on a paper chart. At the end of the rotation, all students took another multiple-choice examination. RESULTS: Of 50 eligible students, 45 agreed to participate in the project, 21 in the treatment group and 24 in the control group. Pre-rotation scores were similar for the two groups (43 percent in the treatment group and 40 percent in the control group; SD, 10 percent). Post-rotation scores were identical for the two groups (65 percent in the treatment group and 65 percent in the control group; SD, 12 percent). A t-test analysis revealed no significant difference in performance on the examinations between the two groups. CONCLUSION: This study did not demonstrate a learning advantage for medical students who have access to educational material on a hospital information system.

Alberta↗
PubMed2004

Glenohumeral deformity in children with internal rotation contractures secondary to brachial plexus birth palsy: intraoperative arthrographic classification.

PURPOSE: To evaluate, with intraoperative arthrography, joint morphology in children undergoing surgical treatment of residual paralysis of the shoulder resulting in brachial plexus birth palsy and to correlate the morphology with the degree of passive external rotation. MATERIALS AND METHODS: In 64 children (age range, 7 months to 13 years 6 months), an orthopedic surgeon performed intraoperative arthrography and measured passive external rotation while the patient received a general anesthetic. The orthopedic surgeon and three radiologists reviewed arthrograms and in consensus classified glenohumeral joints in one of four categories: concentric, with the humeral head well centered on the glenoid fossa; flat, with flattening of the posterior glenoid; biconcave, with the humeral head in articulation with the posterior of two concavities, which were in the same plane; and pseudoglenoid, with the humeral head in articulation with the more posterior of two concavities, with retroversion and in a plane different from that of the anterior concavity. Kruskal-Wallis test was used to compare preoperative external rotation with four appearances of glenoid. RESULTS: Twenty-one children had concentric glenohumeral joints; seven children, flat glenohumeral joints; 19 children, biconcave glenoid; and 17 children, pseudoglenoid. Median passive external rotation was -20 degrees for patients with pseudoglenoid, -10 degrees for those with flat or biconcave glenoids, and 0 degrees for those with concentric glenoids. Presence and type of glenoid deformity were significantly associated with severity of internal rotation contracture (P <.001). CONCLUSION: Consistent patterns of glenohumeral joint deformity in brachial plexus birth palsy were identified and correlated with severity of internal rotation contracture.

Adolescent↗
PubMedDate not supplied

US of the shoulder: non-rotator cuff disorders.

The most common indication for shoulder ultrasonography (US) is the diagnosis of rotator cuff disease. However, there is a spectrum of non-rotator cuff abnormalities that are amenable to US examination, including instability of the biceps tendon, glenohumeral joint, and acromioclavicular joint; arthropathies and bursites (inflammatory diseases, degenerative and infiltrative disorders, infections); nerve entrapment syndromes; and space-occupying lesions. Many of these conditions may be overlooked clinically or can even mimic rotator cuff tears, and US can help redirect the diagnosis if a complete shoulder examination rather than a simple rotator cuff assessment is performed. In addition, US can be remarkably helpful in guiding either needle aspiration procedures or local injection therapy in patients with synovial processes. Although radiography, magnetic resonance (MR) imaging, and computed tomographic and MR arthrography are effective modalities for the evaluation of non-rotator cuff disorders, US is both less costly and less invasive and will likely be used more frequently in this setting as experience increases. Once adequate radiographs have been obtained to exclude apparent bone disorders, high-resolution US should be the first-line imaging modality in the assessment of non-rotator cuff disorders of the shoulder, assuming the study is performed with high-end equipment by an experienced examiner.

Arthritis↗
PubMed2001

Optimized suspension culture: the rotating-wall vessel.

Suspension culture remains a popular modality, which manipulates mechanical culture conditions to maintain the specialized features of cultured cells. The rotating-wall vessel is a suspension culture vessel optimized to produce laminar flow and minimize the mechanical stresses on cell aggregates in culture. This review summarizes the engineering principles, which allow optimal suspension culture conditions to be established, and the boundary conditions, which limit this process. We suggest that to minimize mechanical damage and optimize differentiation of cultured cells, suspension culture should be performed in a solid-body rotation Couette-flow, zero-headspace culture vessel such as the rotating-wall vessel. This provides fluid dynamic operating principles characterized by 1) solid body rotation about a horizontal axis, characterized by colocalization of cells and aggregates of different sedimentation rates, optimally reduced fluid shear and turbulence, and three-dimensional spatial freedom; and 2) oxygenation by diffusion. Optimization of suspension culture is achieved by applying three tradeoffs. First, terminal velocity should be minimized by choosing microcarrier beads and culture media as close in density as possible. Next, rotation in the rotating-wall vessel induces both Coriolis and centrifugal forces, directly dependent on terminal velocity and minimized as terminal velocity is minimized. Last, mass transport of nutrients to a cell in suspension culture depends on both terminal velocity and diffusion of nutrients. In the transduction of mechanical culture conditions into cellular effects, several lines of evidence support a role for multiple molecular mechanisms. These include effects of shear stress, changes in cell cycle and cell death pathways, and upstream regulation of secondary messengers such as protein kinase C. The discipline of suspension culture needs a systematic analysis of the relationship between mechanical culture conditions and biological effects, emphasizing cellular processes important for the industrial production of biological pharmaceuticals and devices.

Animals↗
PubMed1978

Role of primate flocculus during rapid behavioral modification of vestibuloocular reflex. I. Purkinje cell activity during visually guided horizontal smooth-pursuit eye movements and passive head rotation.

1. Extracellular recordings were obtained from 124 Purkinje cells (P-cells) in the flocculus of alert monkeys. P-cell simple spike-firing rate was analyzed quantitatively during various combinations of smooth-pursuit eye movement and passive head rotation. 2. During sinusoidal smooth eye movements, 80% of the P-cells displayed increased firing rate during ipsilateral and 20% during contralateral eye movement. Over the frequency range 0.3--1.4 Hz, firing-rate modulation was proportional to and in phase with maximum eye velocity. During the steady state of triangle-wave tracking, firing rate increased monotonically as a function of eye velocity. Since firing rate was uncorrelated with retinal-error velocity, one component of P-cell firing rate was related to eye velocity. 3. During the transient phase of triangle-wave tracking, when an instantaneous change in the direction of target movement caused a large retinal-error velocity, 40% of the P-cells were related only to eye velocity. Sixty percent of the P-cells displayed an overshoot or undershoot in firing rate, indicating a relationship to either retinal-error velocity or eye acceleration as well as to eye velocity. 4. During the vestibuloocular reflex (VOR), evoked by head rotation in the dark, P-cell firing rate was only weakly modulated. In contrast, when the monkey suppressed the VOR by fixating a target that rotated with him, P-cell rate was deeply modulated. Since the modulation was proportional to and in phase with maximum head velocity, another component of P-cell firing rate was related to head velocity. 5. Of 36 P-cells tested, 35 displayed firing-rate modulation during both suppression of the VOR and smooth-pursuit eye movement. P-cells that reached peak firing rate during ipsilateral head rotation also reached peak firing rate during ipsilateral smooth eye rotation. Average population sensitivitites to head velocity and eye velocity were equal. In three conditions in which eye and head velocity were elicited simultaneously, P-cell firing rate could be predicted by the linear, vector addition of the separate eye and head velocity components of firing rate. Therefore, the relatively weak modulation of P-cell firing rate during the VOR in the dark can be accounted for by the cancellation of equal but opposite head and eye velocity components. 6. The connections of flocculus P-cells to interneurons in the brain stem VOR pathways have been established in other mammals. In the context of those connections, P-cell firing patterns were appropriate to facilitate the eye movements the monkey was required to make. We conclude that the flocculus is important for sustaining any smooth eye movements that are different from those evoked by head rotation in the dark. The eye velocity component may represent an efference copy signal that sustains ongoing eye velocity during smooth pursuit.

Animals↗
PubMed1978

Role of primate flocculus during rapid behavioral modification of vestibuloocular reflex. II. Mossy fiber firing patterns during horizontal head rotation and eye movement.

1. Extracellular recordings were obtained from 113 mossu fibers (MFs) in the flocculus of alert monkeys trained to perform a visual tracking task during sinusoidal, horizontal head rotation. The analysis of MF discharge patterns was designed to allow quantitative comparison of the discharge properties of flocculus MFs with brain stem cell populations from which the MFs might originate and with flocculus Purkinje cells (P-cells). Based on their firing patterns, MFs were divided into two classes. Vestibular MFs discharged in relation to head velocity and, in some cases, also in relation to eye movement. Eye movement MFs discharged only in relation to one or more components of eye movement. 2. Vestibular MFs were subdivided into three classes. Vestibular-only MFs (n = 15) displayed a modulation in firing rate during head rotation but exhibited no relationship to spontaneous eye movements. Vestibular-plus-saccade MFs (n = 14) displayed a modulation in firing rate during head rotation that quantitatively resembled the modulation in vestibular-only MFs. In addition, a pause in firing rate interrupted the vestibular modulation during saccades in one or more directions. Vestibular-plus-position MFs (n = 4) exhibited steady firing rates that were linearly related to horizontal eye position in the absence of vestibular stimulation. Sinusoidal head rotation evoked a modulation ofiring rate above and below the firing rate set by the eye position. 3. during sinusoidal head rotation, vestibular MF firing rate led head velocity by an average of 24 degrees. The amplitude of MF firing-rate modulation increased as a function of the frequency of head rotation and, hence, maximum head velocity. Since these characteristics are similar to those displayed by P-cells during suppression of the VOR, vestibular MFs probably transmit the head velocity component of P-cell firing rate to the flocculus. Based on evidence from other mammals and a quantitative comparison of population discharge characteristics, it is likely that vestibular MFs originate from the vestibular nerve and from cells in the medial vestibular nucleus. 4. Based on their discharge patterns, eye movement MFs were also subdivided into three classes. Burst MFs (n = 14) emitted a high-frequency burst of spikes prior to and during saccades in one or more direction, but were silent during steady fixation. Burst-tonic MFs (n = 53) emitted a burst of spikes prior to saccades in a preferred ("on") direction, ceased firing during saccades in the opposite ("off") direction, and exhibited steady firing rates that increased as steady gaze shifted in the on direction. Tonic MFs (n = 13) displayed steady firing rates that increased as the position of steady gaze shifted in the on direction, and either paused or exhibited step changes in firing rate during saccades. 5. During steady fixation, 64% of tonic and burst-tonic MFs were recruited into maintained firing within +/- 10 degrees of the primary direction of gaze...

Animals↗
PubMedDate not supplied

Psychological impact on house staff of an initial versus subsequent emergency medicine rotation.

The objective of this study was to assess the psychological impact of a 4-week emergency medicine (EM) rotation on residents undergoing their first EM experience. These findings were compared to the psychological impact the rotation had on residents with prior EM experience. Data were obtained from a post hoc analysis of a previous study. Prerotation and postrotation psychological distress levels were assessed over a 4-week EM rotation. Anxiety and depressive symptoms were evaluated by the Brief Symptom Inventory and the Dissociative Experience Scale that together comprise a total of 14 psychometric scales. All scales were given at the beginning and end of the initial EM rotation for the academic year of 1994-1995. All information was coded and confidential. Eighteen junior residents (9/18 EM [50%]) were analyzed as a group and compared to 53 residents (34/51 EM [66%]) with prior exposure to the authors' emergency department. Residents doing their first EM rotation (N = 18) showed improvement in 13 of 14 scales (P = .002). Of the 13 scales that improved, 3 improved significantly: Brief Symptom Inventory = anxiety (P = .002) and Dissociative Experience Scale = absorption (P = .001) and other (P = .001). Residents with prior EM experience (N = 53) displayed worsening in 9 of 13 scales (P = not significant) and no change in 1. Residents undergoing their first EM rotation showed a significant decrease in psychological distress over the 4-week period. Residents with prior EM experience did not show a similar change.

Adult↗
PubMed2002

The effects of rotation on radiographic evaluation of the tibiofibular syndesmosis.

Radiographs of 12 normal cadaveric lower extremities were prepared with each extremity in seven increments of axial rotation, ranging from 5 degrees of external rotation to 25 degrees of internal rotation. The tibiofibular clear space, the tibiofibular overlap, the width of the tibia and fibula, and the medial clear space were measured on each film. The width of the tibiofibular clear space (syndesmosis A) averaged 3.9+/-0.9 mm (range, 2 to 5.5 mm), but did not change significantly with rotation. Its size was independent of the size of tibia and fibula. All other measurements changed dramatically with rotation. In our specimens, a true mortise view of the ankle joint was obtained by internally rotating the extremity an average of 13.6+/-0.7 degrees (range, 12.0 degrees to 17.0 degrees). Based on our results the width of the tibiofibular clear space on the anterior-posterior view is the most reliable parameter for detecting widening of the syndesmosis on plain radiographs. However, due to its variability among different individuals, comparison views of the contralateral extremity are warranted for confirmation of clinical suspicion of syndesmosis disruption.

Analysis of Variance↗
PubMed2000

Sex differences on a mental rotation task: variations in electroencephalogram hemispheric activation between children and college students.

The area of cognitive research that has produced the most consistent sex differences is spatial ability. In particular, men usually perform better on mental rotation tasks than women. Performance on mental rotation tasks has been associated with right parietal activation levels, both during task performance and prior to performance during baseline recordings. This study examined the relations among sex, age, electroencephalogram (EEG) hemispheric activation (at the 10.5 Hz to 13.5 Hz frequency band), and 2-D mental rotation task ability. Nineteen 8-year-olds (10 boys) and 20 college students (10 men) had EEG recorded at baseline and while performing a mental rotation task. Men had a faster reaction time on the mental rotation task than women, whereas there were no differences between boys and girls. After covarying for baseline EEG power values, men exhibited more activation (lower EEG power values) than women in the parietal and posterior temporal regions, whereas boys' and girls' power values did not differ in the parietal or posterior temporal regions. Furthermore, during the baseline condition, men generally exhibited more activation (lower EEG power values) throughout all regions of the scalp. Results support the hypothesis that a change that affects both brain activation and performance on mental rotation tasks occurs sometime between childhood and adulthood.

Adolescent↗
PubMed2005

Clerkship sharing on inpatient internal medicine rotations: an emerging clerkship model.

BACKGROUND: "Clerkship sharing" is the coexistence of students from 2 or more medical schools rotating on the same specialty at a single clerkship site. PURPOSE: Clerkship sharing was characterized by answering three related questions regarding the prevalence of clerkship sharing on internal medicine inpatient rotations, stakeholders views of the advantages and disadvantages of clerkship sharing, and the ways that clerkship sharing affects medical student outcomes at an institution. METHODS: In 2001, the Clerkship Directors in Internal Medicine (CDIM) surveyed its members; 1 section addressed clerkship sharing on inpatient rotations. In addition, the authors surveyed a convenience sample of teachers and learners at 41% of schools with clerkship sharing. Finally, using a 10-year database from one institution, we searched for differences in clerkship outcomes among students who rotated at clerkship sites with or without clerkship sharing. RESULTS: The overall clerkship director (CD) survey response rate was 78% (96/123); 22 of 96 (23%) of CDs reported having clerkship sharing on inpatient rotations. Advantages reported included a greater diversity of clinical exposure for students (77%) and a fostering of collegial relationships (73%). We also collected 79 teacher and 77 medical student surveys from 9 (41%) medical schools identified as having clerkship sharing. The majority of these teachers and learners believed that sharing improves teaching and the overall rotation quality. All surveyed groups were concerned that clerkship sharing affected the clarity of clerkship goals, objectives, and grading. However, clerkship outcomes from 1 institution demonstrated no effect of clerkship sharing on faculty ratings of students or student examination performance. CONCLUSIONS: Clerkship sharing appears to be an emerging clerkship model, and, although it may have inherent advantages that benefit student education, CDs should address challenges such as common goals and expectations for students and teachers.

Clinical Clerkship↗
PubMed1997

Three hundred sixty-degree rotation of the posterior semicircular canal for treatment of benign positional vertigo: a placebo-controlled trial.

The canalithiasis hypothesis proposes that benign positional vertigo (BPV) is caused by dislodged otoconia that settle in the posterior semicircular canal (PSC). When head position is changed these particles move within the canal and induce abnormal endolymph flow. To clear the PSC from debris we developed a procedure that consists of a full circle of backward head rotation in the exact plane of the canal. Patients were seated in a three-dimensional motion device that rotated in steps of 110 degrees every 30 seconds. The first part of the study was conducted as an open trial; the second part followed a single-blinded, placebo-controlled design: Forward rotation (placebo) was applied first and backward rotation was applied 1 week later if BPV persisted. All patients were assessed with a symptom diary and, in the controlled trial, also with the Dix-Hallpike maneuver. In the open study 10 of 15 patients became asymptomatic after one treatment session. In the controlled trial all 15 patients remained symptomatic after forward rotation while 10 of 14 undergoing backward rotation were relieved from positional vertigo immediately (p = 0.004). The presence of secondary nystagmus during the procedure indicated a favorable outcome. Our findings provide evidence for the efficacy of canal-clearing procedures that validate the canalithiasis hypothesis of BPV.

Calculi↗
PubMed1996

Confocal microscopy analysis of living Xenopus eggs and the mechanism of cortical rotation.

The dorsoventral body axis in amphibian embryos is established by a rotation of the outer cortex relative to the inner cytoplasmic core. This cortical rotation depends on microtubules and is correlated with a parallel array of microtubules just inside the vegetal cortex. Since the parallel array moves with the inner cytoplasm and most of its microtubules are oriented with their plus ends facing the direction of cortical movement, it has been suggested that plus end-directed motor molecules attached to the cortex drive the rotation by moving along microtubules of the parallel array. Using an inverted confocal microscope to examine living eggs, however, we found that rotation movements precede the formation of a detectable parallel array at the vegetal pole, that the parallel array consists of multiple layers of microtubules at depths ranging from 4 to 8 microns inside the plasma membrane and that the velocity of rotation is immobilized eggs increases with depth in this region. These findings suggest that (1) early cytoplasmic movements are due to something other than the fully formed parallel array and (2) the motor molecules responsible for the bulk of the rotation movement are not restricted to a monolayer at the subcortical interface but may be distributed throughout the parallel array, perhaps causing microtubules to slide along other microtubules by a mechanism similar to that seen in cilia and eukaryotic flagella.

Animals↗
PubMed1997

The contractile properties of the M. supracoracoideus In the pigeon and starling: a case for long-axis rotation of the humerus

Wing upstroke in birds capable of powered flight is kinematically the most complicated phase of the wingbeat cycle. The M. supracoracoideus (SC), generally considered to be the primary elevator of the wing, is a muscle with a highly derived but stereotyped morphology in modern flying birds. The contractile portion of the SC arises from a ventral sternum, but its tendon of insertion courses above the glenohumeral joint to insert on the dorsal surface of the humerus. To clarify the role of the SC during wing upstroke, we studied its contractile and mechanical properties in European starlings (Sturnus vulgaris) and pigeons (Columba livia), two birds with contrasting flight styles. We made in situ measurements of isometric forces of humeral elevation and humeral rotation and, in addition, measured the extent of unrestrained humeral excursion during stimulation of the muscle nerve. We also generated passive and active length-force curves for the SC of each species. Stimulation of the SC at humeral joint angles of elevation/depression and protraction/retraction coincident with the downstroke-upstroke transition and mid-upstroke produced substantially higher forces of long-axis rotation than elevation. When the humerus was allowed to move (rotate/elevate) during stimulation, we observed rotation about its longitudinal axis of up to 70-80 degrees , but humeral elevations of only 40-60 degrees above the horizontal (as measured in lateral view). In the active length-force experiments, we measured mean (+/-s.d.) maximal tetanic forces of 6.5+/-1.2 N for starlings (N=4) and 39.4+/-6.2 N for pigeons (N=6), unexpectedly high forces approximately 10 times body weight. The working range of the SC in both species corresponds to the ascending limb (but not the plateau) of the active length-force curve. The potential for greatest active force is high on the ascending limb at joint angles coincident with the downstroke-upstroke transition, a time when the humerus is depressed below the horizontal and rotated forward maximally. As the SC shortens to counterrotate and elevate the humerus during early upstroke, the potential for active force at shorter lengths declines at a relatively rapid rate. These findings reveal that the primary role of the SC is to impart a high-velocity rotation of the humerus about its longitudinal axis, which rapidly elevates the distal wing. This rapid twisting of the humerus is responsible for positioning the forearm and hand so that their subsequent extension orients the outstretched wing in the parasagittal plane appropriate for the subsequent downstroke. We propose that, at the downstroke-upstroke transition, variable levels of co-contraction of the M. pectoralis and SC interact to provide a level of kinematic control at the shoulder that would not be possible were the two antagonists to work independently. The lack of a morphologically derived SC in Late Jurassic and Early Cretaceous birds precluded a high-velocity recovery stroke which undoubtedly limited powered flight in these forms. Subsequent evolution of the derived SC capable of imparting a large rotational force to the humerus about its longitudinal axis was an important step in the evolution of the wing upstroke and in the ability to supinate (circumflex) the manus in early upstroke, a movement fundamental to reducing air resistance during the recovery stroke.

Journal Article↗
PubMed2003

Assessment of web-based applications for ambulatory care rotations.

BACKGROUND: An interactive Web site was developed to supplement ambulatory care clinical rotations, optimize collaborative efforts of ambulatory care preceptors, and standardize the educational and evaluation experience. OBJECTIVE: To evaluate perceptions of residents and students using an interactive Web site for ambulatory care clinical pharmacy rotations. METHODS: An online anonymous survey comprised of 12 questions using a 5-point Likert scale (1-5, strongly disagree-strongly agree) and 4 open-ended questions was designed. Over a 3-year time frame, each student and resident rotating through the ambulatory care clinical rotation was instructed to complete the survey at the end of the rotation experience. Survey results were compiled and analyzed. RESULTS: Sixty-nine percent (18/26) of residents and 71% (54/76) of students completed the survey. Overall, the Web site was well accepted by all learners. Residents and students differed in opinion on a few aspects of the Web site; however, both appreciated the ease of accessibility and links to additional resources. Inoperable links and outdated quizzes were identified as major weaknesses. CONCLUSIONS: Perceptions of an interactive Web site used during ambulatory care clinical rotations were positive. The survey results reinforce the continued use of this teaching method and will enable preceptors to make appropriate adjustments for future learners.

Ambulatory Care↗
PubMed2004

Jones matrix for image-rotation prisms.

The polarization-transforming properties of rotational prisms are analyzed with polarized light by using the Jones calculus and the exact ray-trace. A general expression of the Jones matrix for a rotational prism is derived, incorporating an explicit dependence on the image-rotation angle or the wave-front-rotation angle. The Jones matrix for the Pechan, Dove, Reversion, and Delta prisms is derived where the explicit dependence on the angle of rotation of the image is given. An experiment with a rotating Dove prism is also conducted to determine the output states of polarization for incident linearly polarized light. Experimental results agree with theoretical expectations.

Journal Article↗
PubMed2005

Daytime operation of a pure rotational Raman lidar by use of a Fabry-Perot interferometer.

We propose to use a Fabry-Perot interferometer (FPI) in a pure rotational Raman lidar to isolate return signals that are due to pure rotational Raman scattering from atmospheric nitrogen against the sky background. The main idea of this instrumental approach is that a FPI is applied as a frequency comb filter with the transmission peaks accurately matched to a comb of practically equidistant lines of a pure rotational Raman spectrum (PRRS) of nitrogen molecules. Thus a matched FPI transmission comb cuts out the spectrally continuous sky background light from the spectral gaps between the PRRS lines of nitrogen molecules while it is transparent to light within narrow spectral intervals about these lines. As the width of the spectral gaps between the lines of the PRRS of nitrogen molecules is -114 times the width of an individual spectral line, cutting out of the sky background from these gaps drastically improves the signal-to-background ratio of the pure rotational Raman lidar returns. This application of the FPI enables one to achieve daytime temperature profiling in the atmosphere with a pure rotational Raman lidar in the visible and near-UV spectral regions. We present an analysis of application of the FPI to filtering out the pure rotational Raman lidar returns against the solar background. To demonstrate the feasibility of the approach proposed, we present temperature profiles acquired during a whole-day measurement session in which a Raman lidar equipped with a FPI was used. For comparison, temperature profiles acquired with Vaisala radiosondes launched from the measurement site are also presented.

Journal Article↗
PubMed2006

Hydrodynamics of rotating liquid mirrors. I. Synchronous disturbances.

The effects of axis alignment errors, planetary rotation, and tidal forces on rotating liquid mirrors are analyzed. These produce a surface distortion that decreases exponentially with distance inward from the rim with a characteristic length l= square root of 3hf/2, where h is the thickness of the fluid and f is the focal length. Even a small tilt of the rotation axis can produce a significant deformation of the optical surface. The maximum surface height error is 3epsilonl, where epsilon is the tilt angle and is typically of the order of 1.5 microm for a 1 arc sec tilt. The main optical effect of the wave is to produce a ring, with angular diameter 6epsilon, offset by half of the diameter in the direction opposite the tilt. This diamond ring aberration can be avoided by accurate alignment of the rotation axis or by masking the outer few centimeters of the mirror. Planetary rotation produces a small deformation of the order of 100 nm for a 10 m telescope at low latitude on Earth. This deformation can be canceled by a small tilt of the rotation axis. Tidal forces produced by the Moon, or by the Earth in the case of a lunar telescope, produce an inconsequential, subnanometer, surface deformation.

Journal Article↗