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Frontal plane hip and ankle sensorimotor function, not age, predicts unipedal stance time  

PubMed Central

Introduction Changes occur in muscles and nerves with aging. This study aimed to explore the relationship between unipedal stance time (UST) and frontal plane hip and ankle sensorimotor function in subjects with diabetic neuropathy. Methods UST, quantitative measures of frontal plane ankle proprioceptive thresholds, and ankle and hip motor function were tested in forty-one persons with a spectrum of lower limb sensorimotor function, ranging from healthy to moderately severe diabetic neuropathy. Results Frontal plane hip and ankle sensorimotor function demonstrated significant relationships with UST. Multivariate analysis identified only composite hip strength, composite ankle proprioceptive threshold, and age to be significant predictors of UST (R2=0.73); they explained 46%, 24% and 3% of the variance, respectively. Discussion/Conclusions Frontal plane hip strength was the single best predictor of UST and appeared to compensate for less precise ankle proprioceptive thresholds. This finding is clinically relevant given the possibility of strengthening the hip, even in patients with significant PN. . PMID:22431092

Allet, Lara; Kim, Hogene; Ashton-Miller, James; De Mott, Trina; Richardson, James K.



Unipedal stance testing in the assessment of peripheral neuropathy  

Microsoft Academic Search

Hurvitz EA, Richardson JK, Werner RA. Unipedal stance testing in the assessment of peripheral neuropathy. Arch Phys Med Rehabil 2001;82:198-204 Objective: To define further the relation between unipedal stance testing and peripheral neuropathy. Design: Prospective cohort. Setting: Electroneuromyography laboratory of a Veterans Affairs medical center and a university hospital. Patients: Ninety-two patients referred for lower extremity electrodiagnostic studies. Main Outcome

Edward A. Hurvitz; James K. Richardson; Robert A. Werner



Force-controlled biting alters postural control in bipedal and unipedal stance.  


Human posture is characterised by inherent body sway which forces the sensory and motor systems to counter the destabilising oscillations. Although the potential of biting to increase postural stability has recently been reported, the mechanisms by which the craniomandibular system (CMS) and the motor systems for human postural control are functionally coupled are not yet fully understood. The purpose of our study was, therefore, to investigate the effect of submaximum biting on postural stability and on the kinematics of the trunk and head. Twelve healthy young adults performed force-controlled biting (FB) and non-biting (NB) during bipedal narrow stance and single-leg stance. Postural stability was quantified on the basis of centre of pressure (COP) displacements, detected by use of a force platform. Trunk and head kinematics were investigated by biomechanical motion analysis, and bite forces were measured using a hydrostatic system. The results revealed that FB significantly improved postural control in terms of reduced COP displacements, providing additional evidence for the functional coupling of the CMS and human posture. Our study also showed, for the first time, that reductions in the sway of the COP were accompanied by reduced trunk and head oscillations, which might be attributable to enhanced trunk stiffness during FB. This physiological response to isometric activation of the masticatory muscles raises questions about the potential of oral motor activity as a strategy to reduce the risk of falls among the elderly or among patients with compromised postural control. PMID:25354425

Ringhof, S; Stein, T; Potthast, W; Schindler, H-J; Hellmann, D



Effects of focal ankle joint cooling on unipedal static balance in individuals with and without chronic ankle instability.  


Application of cryotherapy over an injured joint has been shown to improve muscle function, yet it is unknown how ankle cryotherapy affects postural control. Our purpose was to determine the effects of a 20-min focal ankle joint cooling on unipedal static stance in individuals with and without chronic ankle instability (CAI). Fifteen young subjects with CAI (9 males, 6 females) and 15 healthy gender-matched controls participated. All subjects underwent two intervention sessions on different days in which they had a 1.5L plastic bag filled with either crushed ice (active treatment) or candy corn (sham) applied to the ankle. Unipedal stance with eyes closed for 10s were assessed with a forceplate before and after each intervention. Center of pressure (COP) data were used to compute 10 specific dependent measures including velocity, area, standard deviation (SD), and percent range of COP excursions, and mean and SD of time-to-boundary (TTB) minima in the anterior-posterior (AP) and mediolateral directions. For each measure a three-way (Group-Intervention-Time) repeated ANOVAs found no significant interactions and main effects involving intervention (all Ps>0.05). There were group main effects found for mean velocity (F(1,28)=6.46, P=.017), area (F(1,28)=12.83, P=.001), and mean of TTB minima in the AP direction (F(1,28)=5.19, P=.031) indicating that the CAI group demonstrated greater postural instability compared to the healthy group. Postural control of unipedal stance was not significantly altered following focal ankle joint cooling in groups both with and without CAI. Ankle joint cryotherapy was neither beneficial nor harmful to single leg balance. PMID:25468685

Kim, Kyung-Min; Hart, Joseph M; Saliba, Susan A; Hertel, Jay



A cane reduces loss of balance in patients with peripheral neuropathy: Results from a challenging unipedal balance test  

Microsoft Academic Search

Objective: To test the hypothesis that use of a cane in the nondominant hand during challenging balance tasks would significantly decrease loss of balance in patients with peripheral neuropathy while transferring from bipedal to unipedal stance on an unsteady surface.Design: Nonrandomized control study.Setting: Tertiary-care institution.Participants Eight consecutive patients with peripheral neuropathy (PN) and eight age- and gender-matched controls (C) with

James A. Ashton-Miller; Mark W. L. Yeh; James K. Richardson; Todd Galloway



Soccer players have a better standing balance in nondominant one-legged stance  

PubMed Central

The purpose of this study was to analyze the differences in standing balance during dominant and nondominant one-legged stance among athletes of different sports and sedentary subjects. The right-footed subjects of four groups (sedentary, n = 20; soccer, n = 20; basketball, n = 20; windsurfer n = 20) underwent 5-sec unipedal (left and right foot) stabilometric analysis with open eyes and closed eyes to measure center of pressure (COP) sway path and COP velocity (mean value, anteroposterior, and laterolateral in millimeters per second). The soccer group showed better standing balance on the left leg than the sedentary group (P < 0.05). No other significant differences were observed within and amongst groups. The soccer players have a better standing balance on the nondominant leg because of soccer activity. PMID:24198563

Barone, Rosario; Macaluso, Filippo; Traina, Marcello; Leonardi, Vincenza; Farina, Felicia; Di Felice, Valentina



Stance duration under sensory conflict conditions in patients with hemiplegia.  


Standing balance was evaluated in ten subjects with hemiplegia using a sensory organization balance test (SOT). The SOT is a timed balance test which evaluates somatosensory, visual, and vestibular function for maintenance of upright posture. The duration of bilateral stance was assessed using combinations of three visual and two support surface conditions. Stance time was measured with eyes open, eyes closed, and with each patient wearing a visual dome to produce inaccurate visual information. The support surface conditions involved stance on a hard flat floor followed by attempted stance on a compliant foam surface. Visual deprivation or visual conflict conditions did not cause a loss of balance when stance was performed on a stable surface. However, a lower stance duration was found when patients stood on a compliant surface (p less than .05). Visual compensation was evident during the compliant-surface condition because stance duration showed the greatest reductions with eyes closed and with the visual dome. These findings suggest that the ability to integrate somatosensory information from the lower extremities for balance is compromised after cerebrovascular disease. The implications for diagnosing the specific cause of balance dysfunction and for developing sensory-specific therapeutic interventions are discussed. PMID:2009045

Di Fabio, R P; Badke, M B



Subjectivity, intersubjectivity and the historical construction of interlocutor stance: from stance markers to discourse markers  

Microsoft Academic Search

This study draws upon the techniques of corpus linguistics, discourse analysis and historical pragmatics to provide an account of the ways in which speakers recruit markers of epistemic stance to capture their construction of the attitudes of their interlocutors, addressees, or audience. It then examines the ways in which selected markers lose their subjective force over time, whether expressive of

Susan Fitzmaurice



Feedforward ankle strategy of balance during quiet stance in adults  

PubMed Central

We studied quiet stance investigating strategies for maintaining balance. Normal subjects stood with natural stance and with feet together, with eyes open or closed. Kinematic, kinetic and EMG data were evaluated and cross-correlated.Cross-correlation analysis revealed a high, positive, zero-phased correlation between anteroposterior motions of the centre of gravity (COG) and centre of pressure (COP), head and COG, and between linear motions of the shoulder and knee in both sagittal and frontal planes. There was a moderate, negative, zero-phased correlation between the anteroposterior motion of COP and ankle angular motion.Narrow stance width increased ankle angular motion, hip angular motion, mediolateral sway of the COG, and the correlation between linear motions of the shoulder and knee in the frontal plane. Correlations between COG and COP and linear motions of the shoulder and knee in the sagittal plane were decreased. The correlation between the hip angular sway in the sagittal and frontal planes was dependent on interaction between support and vision.Low, significant positive correlations with time lags of the maximum of cross-correlation of 250-300 ms were found between the EMG activity of the lateral gastrocnemius muscle and anteroposterior motions of the COG and COP during normal stance. Narrow stance width decreased both correlations whereas absence of vision increased the correlation with COP.Ankle mechanisms dominate during normal stance especially in the sagittal plane. Narrow stance width decreased the role of the ankle and increased the role of hip mechanisms in the sagittal plane, while in the frontal plane both increased.The modulation pattern of the lateral gastrocnemius muscle suggests a central program of control of the ankle joint stiffness working to predict the loading pattern. PMID:9882761

Gatev, Plamen; Thomas, Sherry; Kepple, Thomas; Hallett, Mark



Feedforward ankle strategy of balance during quiet stance in adults.  


1. We studied quiet stance investigating strategies for maintaining balance. Normal subjects stood with natural stance and with feet together, with eyes open or closed. Kinematic, kinetic and EMG data were evaluated and cross-correlated. 2. Cross-correlation analysis revealed a high, positive, zero-phased correlation between anteroposterior motions of the centre of gravity (COG) and centre of pressure (COP), head and COG, and between linear motions of the shoulder and knee in both sagittal and frontal planes. There was a moderate, negative, zero-phased correlation between the anteroposterior motion of COP and ankle angular motion. 3. Narrow stance width increased ankle angular motion, hip angular motion, mediolateral sway of the COG, and the correlation between linear motions of the shoulder and knee in the frontal plane. Correlations between COG and COP and linear motions of the shoulder and knee in the sagittal plane were decreased. The correlation between the hip angular sway in the sagittal and frontal planes was dependent on interaction between support and vision. 4. Low, significant positive correlations with time lags of the maximum of cross-correlation of 250-300 ms were found between the EMG activity of the lateral gastrocnemius muscle and anteroposterior motions of the COG and COP during normal stance. Narrow stance width decreased both correlations whereas absence of vision increased the correlation with COP. 5. Ankle mechanisms dominate during normal stance especially in the sagittal plane. Narrow stance width decreased the role of the ankle and increased the role of hip mechanisms in the sagittal plane, while in the frontal plane both increased. 6. The modulation pattern of the lateral gastrocnemius muscle suggests a central program of control of the ankle joint stiffness working to predict the loading pattern. PMID:9882761

Gatev, P; Thomas, S; Kepple, T; Hallett, M



Comparison of Human and Humanoid Robot Control of Upright Stance  

PubMed Central

There is considerable recent interest in developing humanoid robots. An important substrate for many motor actions in both humans and biped robots is the ability to maintain a statically or dynamically stable posture. Given the success of the human design, one would expect there are lessons to be learned in formulating a postural control mechanism for robots. In this study we limit ourselves to considering the problem of maintaining upright stance. Human stance control is compared to a suggested method for robot stance control called zero moment point (ZMP) compensation. Results from experimental and modeling studies suggest there are two important subsystems that account for the low- and mid-frequency (DC to ~1 Hz) dynamic characteristics of human stance control. These subsystems are 1) a “sensory integration” mechanism whereby orientation information from multiple sensory systems encoding body kinematics (i.e. position, velocity) is flexibly combined to provide an overall estimate of body orientation while allowing adjustments (sensory re-weighting) that compensate for changing environmental conditions, and 2) an “effort control” mechanism that uses kinetic-related (i.e., force-related) sensory information to reduce the mean deviation of body orientation from upright. Functionally, ZMP compensation is directly analogous to how humans appear to use kinetic feedback to modify the main sensory integration feedback loop controlling body orientation. However, a flexible sensory integration mechanism is missing from robot control leaving the robot vulnerable to instability in conditions were humans are able to maintain stance. We suggest the addition of a simple form of sensory integration to improve robot stance control. We also investigate how the biological constraint of feedback time delay influences the human stance control design. The human system may serve as a guide for improved robot control, but should not be directly copied because the constraints on robot and human control are different. PMID:19665564

Peterka, Robert J.



Individuals with diminished hip abductor muscle strength exhibit altered ankle biomechanics and neuromuscular activation during unipedal balance tasks.  


Coordinated control of the hip and ankle is important for maintaining postural stability. The purpose of the study was to compare postural stability between individuals with contrasting hip abductor strength during unipedal balance tasks and to determine whether diminished hip abductor strength results in greater utilization of the ankle strategy to maintain balance. Forty-five females (276±35 years) participated in the study. Participants were ranked based on their isometric hip abductor muscle strength. The top 33% of the participants were categorized as the strong group (n=15) and the lower 33% as the weak group (n=15). Each subject performed a static and a dynamic unipedal balance task, during which mean COP displacement, peak ankle invertor and evertor moments, and neuromuscular activation of the lower leg muscles were assessed. Two-way mixed analyses of variance tests with task as a repeated factor were performed to detect the effects of task and group on the variables of interest. When averaged across tasks, mean medial-lateral COP displacement was significantly greater in the weak group (136±117 vs. 98±60 mm, p=0.05). The weak group also exhibited greater peak ankle invertor and evertor moments (0.31±0.10 vs. 0.25±0.11 Nm/kg, p=0.03; 0.04±0.06 vs. -0.02±0.07 Nm/kg, p=0.01), and increased peroneus longus activation (46±12 vs. 36±15%, p<0.01). Our results demonstrate that individuals with diminished hip abductor muscle strength demonstrated decreased medial-lateral postural stability, and exhibited a shift toward utilizing an ankle strategy to maintain balance during unipedal tasks. PMID:24373699

Lee, Szu-Ping; Powers, Christopher M



Stance width influences frontal plane balance responses to centripetal accelerations.  


Whenever the body is moving in a curvilinear path, inertial torques resulting from centripetal accelerations act on the body and must be counteracted to maintain stability. We tested the hypothesis that healthy subjects orient their center of mass in the position where gravitational torques offset the inertial torques due to centripetal accelerations. Ten healthy subjects stood on a platform that rotated in a circle at either a slow or fast speed, eyes open or closed, and in narrow or wide stance. Upper body, lower body, and center of mass (CoM) tilt with respect to vertical were measured and averaged across a 40 second time period of constant velocity. Body tilt was compared to the gravito-inertial acceleration (GIA) angle with respect to vertical. In all moving conditions, the upper body, lower body, and CoM tilted inward. However, this inward tilt did not reach the predicted GIA angle (CoM tilt was ~78% and 39% toward the predicted GIA angle in narrow and wide stance, respectively). Ratios of body tilt to GIA angle were minimally influenced by visual availability and magnitude of centripetal acceleration; but were largely influenced by stance width whereby narrow stance inward tilt was greater than wide stance. These results further highlight the important influence of the base of support on balance control strategies and enhance our understanding of how the balance control system compensates for inertial torques generated from centripetal accelerations. PMID:22819010

Goodworth, Adam; Chandan, Aditi; Chase, Hannah; Foster, Elizabeth; Francoeur, Heather; Michaud, Jenna; Terry, Kathryn



Statistical analysis of quiet stance sway in 2-D.  


Subjects exposed to a rotating environment that perturbs their postural sway show adaptive changes in their voluntary spatially directed postural motion to restore accurate movement paths but do not exhibit any obvious learning during passive stance. We have found, however, that a variable known to characterize the degree of stochasticity in quiet stance can also reveal subtle learning phenomena in passive stance. We extended Chow and Collins (Phys Rev E 52(1):909-912, 1995) one-dimensional pinned-polymer model (PPM) to two dimensions (2-D) and then evaluated the model's ability to make analytical predictions for 2-D quiet stance. To test the model, we tracked center of mass and centers of foot pressures, and compared and contrasted stance sway for the anterior-posterior versus medio-lateral directions before, during, and after exposure to rotation at 10 rpm. Sway of the body during rotation generated Coriolis forces that acted perpendicular to the direction of sway. We found significant adaptive changes for three characteristic features of the mean square displacement (MSD) function: the exponent of the power law defined at short time scales, the proportionality constant of the power law, and the saturation plateau value defined at longer time scales. The exponent of the power law of MSD at a short time scale lies within the bounds predicted by the 2-D PPM. The change in MSD during exposure to rotation also had a power-law exponent in the range predicted by the theoretical model. We discuss the Coriolis force paradigm for studying postural and movement control and the applicability of the PPM model in 2-D for studying postural adaptation. PMID:24477760

Bakshi, Avijit; DiZio, Paul; Lackner, James R



Using a Stance Corpus to Learn about Effective Authorial Stance-Taking: A Textlinguistic Approach  

ERIC Educational Resources Information Center

Presenting a persuasive authorial stance is a major challenge for second language (L2) writers in writing academic research. Failure to present an effective authorial stance often results in poor evaluation, which compromises a writer's research potential. This study proposes a "textlinguistic" approach to advanced academic writing to complement a…

Chang, Peichin



Characterizing Postural Sway during Quiet Stance Based on the Intermittent Control Hypothesis  

NASA Astrophysics Data System (ADS)

This article illustrates a signal processing methodology for the time series of postural sway and accompanied electromyographs from the lower limb muscles during quiet stance. It was shown that the proposed methodology was capable of identifying the underlying postural control mechanisms. A preliminary application of the methodology provided evidence that supports the intermittent control hypothesis alternative to the conventional stiffness control hypothesis during human quiet upright stance.

Nomura, Taishin; Nakamura, Toru; Fukada, Kei; Sakoda, Saburo



Stability of a double inverted pendulum model during human quiet stance with continuous delay feedback control.  


Recent debate about neural mechanisms for stabilizing human upright quiet stance focuses on whether the active and time delay neural feedback control generating muscle torque is continuous or intermittent. A single inverted pendulum controlled by the active torque actuating the ankle joint has often been used for the debate on the presumption of well-known ankle strategy hypothesis claiming that the upright quiet stance can be stabilized mostly by the ankle torque. However, detailed measurements are showing that the hip joint angle exhibits amount of fluctuations comparable with the ankle joint angle during natural postural sway. Here we analyze a double inverted pendulum model during human quiet stance to demonstrate that the conventional proportional and derivative delay feedback control, i.e., the continuous delay PD control with gains in the physiologically plausible range is far from adequate as the neural mechanism for stabilizing human upright quiet stance. PMID:22256061

Suzuki, Yasuyuki; Nomura, Taishin; Morasso, Pietro



Ratite Footprints and the Stance and Gait  

E-print Network

footprints of the Mesozoic Era attributed to theropod dinosaurs. Of par- ticular interest,'(i) the rheaRatite Footprints and the Stance and Gait of Mesozoic Theropods KEVIN PADIAN AND PAUL E. OLSEN, and the toes and claws leave no drag marks. These are all characteristic of Mesozoic theropod (and ornithopod

Olsen, Paul E.


Stance in Spoken and Written University Registers  

ERIC Educational Resources Information Center

Numerous studies have investigated the linguistic expression of stance and evaluation in university registers, focusing especially on academic research writing and to a lesser extent classroom teaching. The present study extends previous research in two ways: (1) it compares and contrasts the use of a wide range of lexico-grammatical features used…

Biber, Douglas



Reader Stance: Whose Choice Is It?  

ERIC Educational Resources Information Center

A recurring theme within the prolific body of research on reader response is that of reader stance. Although several prominent theories of reader response spring from different perspectives, they share one common property: each describes reader response in terms of two opposed domains with particular responses falling somewhere on a continuum…

Peck, Jackie


Kinematics of the distal hindlimb during stance phase in the fast trotting standardbred.  


Fast trotting Standardbred horses were filmed along a straight on an oval dirt track. Five consecutive stance phases were analysed to describe the planar kinematics of the distal hindlimb. The rapid changes in the geometry of the distal hindlimb that occur during the early stance phase were studied. The hoof segment was initially braked vertically and moved in the direction of the horse. The hoof moved forward on the track surface for more than 20% of the stance time (ST). Two specific deviations in the otherwise smooth course of the fetlock joint angle appeared at 16 and 29% of ST. Tarsal angular joint displacement was, on the other hand, more smooth throughout the stance phase. Segment angular velocity was greatest in the proximal pastern segment, while the metatarsus was almost totally braked in its forward rotation during the early stance. Tibial angular velocity was more smooth and greater than that of the metatarsus. Initial vertical braking of the hoof was related to the rapid rotation of the proximal pastern segment, while the metatarsal and proximal pastern segment angular velocities decreased as the hoof was braked horizontally. Also coincident with horizontal braking of the hoof was an increase in the angular velocity of the tibial segment. It was concluded that the horizontal as well as the vertical braking of the hoof affect the disto-proximal braking of the segments of the distal hindlimb during the early stance phase. The early stance phase changes in the distal hindlimb suggest rapid changes in the internal forces of the limb and should be of importance to the orthopaedic health of Standardbred trotters. These rapid changes at the fetlock joint and hock joint during the early stance may be important in lameness as excessive rapid and repetitive loading and movement are thought to induce joint damage (Radin et al. 1991). PMID:8818591

Johnston, C; Roepstorff, L; Drevemo, S; Kallings, P



Postural fluctuations during pointing from a unilateral or bilateral stance.  


An experiment was conducted to compare the effects of bilateral and unilateral stance on postural fluctuations and intralimb coordination during active balance control. Fifteen participants stood bilaterally and unilaterally while conducting a pointing task with an outstretched arm. Excursion of center of foot pressure (CoP) and limb movements were recorded with a force plate and eight dual-axis accelerometers, respectively. Compared to bilateral stance, unilateral stance resulted in wider CoP trajectories and greater postural fluctuations, especially in the lower limbs. The limb-dependent postural fluctuations during unilateral stance were associated with an increased coupling between the upper limb segments and a decreased coupling between the segments of the stance leg. Unilateral stance further resulted in greater regularity and spectral changes in postural fluctuations of the trunk and lower limb due to increased central oscillations (8-15 Hz). The observed structural differences in postural fluctuations between unilateral and bilateral stance strongly suggested that the postural control system modulates joint stiffness in a stance-dependent manner. Probably, in unilateral stance, attentive control was shifted to the stance leg at the expense of increasing arm stiffness to reduce movement redundancy. PMID:16458377

Hwang, Ing-Shiou; Huang, Chien-Ting; Cherng, Rong-Ju; Huang, Chien-Chun



Stance controlled knee flexion improves stimulation driven walking after spinal cord injury  

PubMed Central

Background Functional neuromuscular stimulation (FNS) restores walking function after paralysis from spinal cord injury via electrical activation of muscles in a coordinated fashion. Combining FNS with a controllable orthosis to create a hybrid neuroprosthesis (HNP) has the potential to extend walking distance and time by mechanically locking the knee joint during stance to allow knee extensor muscle to rest with stimulation turned off. Recent efforts have focused on creating advanced HNPs which couple joint motion (e.g., hip and knee or knee and ankle) to improve joint coordination during swing phase while maintaining a stiff-leg during stance phase. Methods The goal of this study was to investigate the effects of incorporating stance controlled knee flexion during loading response and pre-swing phases on restored gait. Knee control in the HNP was achieved by a specially designed variable impedance knee mechanism (VIKM). One subject with a T7 level spinal cord injury was enrolled and served as his own control in examining two techniques to restore level over-ground walking: FNS-only (which retained a stiff knee during stance) and VIKM-HNP (which allowed controlled knee motion during stance). The stimulation pattern driving the walking motion remained the same for both techniques; the only difference was that knee extensor stimulation was constant during stance with FNS-only and modulated together with the VIKM to control knee motion during stance with VIKM-HNP. Results Stance phase knee angle was more natural during VIKM-HNP gait while knee hyperextension persisted during stiff-legged FNS-only walking. During loading response phase, vertical ground reaction force was less impulsive and instantaneous gait speed was increased with VIKM-HNP, suggesting that knee flexion assisted in weight transfer to the leading limb. Enhanced knee flexion during pre-swing phase also aided flexion during swing, especially when response to stimulation was compromised. Conclusions These results show the potential advantages of incorporating stance controlled knee flexion into a hybrid neuroprosthesis for walking. The addition of such control to FNS driven walking could also enable non-level walking tasks such as uneven terrain, slope navigation and stair descent where controlled knee flexion during weight bearing is critical. PMID:23826711



Assessing Muscle Stiffness from Quiet Stance in Parkinson's Disease  

E-print Network

Assessing Muscle Stiffness from Quiet Stance in Parkinson's Disease Michael Lauk 1;2;4 , MSc Stiffness from Quiet Stance: Applicability to Parkinson's Disease Abstract In previous studies, we developed this measure to patients with Parkinson's disease (PD). We correlated the postural stiffness measure


Stance, Navigation, and Reader Response in Expository Hypertext  

ERIC Educational Resources Information Center

This article reports on two studies investigating reader stance, navigation, and response in expository hypertext. Subjects in the studies included 69 and 147 adult readers prompted to adopt either an efferent or aesthetic stance when reading a 36-node expository hypertext. Reading was followed by recall and essay writing tasks. Results of the…

McEneaney, John E.; Li, Ledong; Allen, Kris; Guzniczak, Lizabeth



Soleus H-reflex modulation during receive stance in badminton players in the receive stance  

PubMed Central

[Purpose] This study aimed to clarify the characteristics of motor neuron excitability by examining the soleus H-reflex in the ready position adopted immediately before making a return during badminton games. [Subjects] Sixteen individuals with (badminton group) and 16 without (control group) experience of playing badminton were studied. [Methods] Each subject was instructed to take up various stances for returning a shuttlecock to measure the H- and M-waves in the soleus. [Results] The H-wave was significantly decreased when gripping a racket was held in the dominant hand than compared to just standing in the badminton group. In contrast, in the control group, no significant differences were observed between when standing and the other stances. [Conclusion] Based on these results, the excitability of spinal motor neurons may have been reduced (H-wave suppression) by badminton training to increase the instantaneous force (power training). PMID:25642054

Masu, Yujiro; Muramatsu, Ken



Changes in plantar pressures during bipedal stance with different stance width.  


We studied the influence of stance width and vision on the plantar pressures for the left and right foot during bipedal quiet standing on the pressure-sensitive insoles. The support widening shifted the left and right centers-of-foot-pressure (CFPs) laterally and forward (right foot), diminished SDs of: the left and right mean plantar pressures (MPPs), the anteroposterior and mediolateral displacements of left and right CFPs. It also decreased negative correlations between left and right MPPs and between mediolateral displacements of left and right CFP and increased positive correlation between anteroposterior displacements of left and right CFPs, more expressive with eyes-open. The later results suggested that support widening increased the weight of exploratory behaviour regarding anteroposterior equilibrium and decreased exploratory sway serving mediolateral equilibrium. Eyes' closure lead to a small left bias of the body-weight-bearing and forward shift of the left versus right CFP, thus suggesting that vision increased bilateral symmetry of stance. PMID:11695525

Gatev, P; Koleva, V; Petkova, G; Dimitrova, D; Ilieva, L



Effect of stance width on multidirectional postural responses  

NASA Technical Reports Server (NTRS)

The effect of stance width on postural responses to 12 different directions of surface translations was examined. Postural responses were characterized by recording 11 lower limb and trunk muscles, body kinematics, and forces exerted under each foot of 7 healthy subjects while they were subjected to horizontal surface translations in 12 different, randomly presented directions. A quasi-static approach of force analysis was done, examining force integrals in three different epochs (background, passive, and active periods). The latency and amplitude of muscle responses were quantified for each direction, and muscle tuning curves were used to determine the spatial activation patterns for each muscle. The results demonstrate that the horizontal force constraint exerted at the ground was lessened in the wide, compared with narrow, stance for humans, a similar finding to that reported by Macpherson for cats. Despite more trunk displacement in narrow stance, there were no significant changes in body center of mass (CoM) displacement due to large changes in center of pressure (CoP), especially in response to lateral translations. Electromyographic (EMG) magnitude decreased for all directions in wide stance, particularly for the more proximal muscles, whereas latencies remained the same from narrow to wide stance. Equilibrium control in narrow stance was more of an active postural strategy that included regulating the loading/unloading of the limbs and the direction of horizontal force vectors. In wide stance, equilibrium control relied more on an increase in passive stiffness resulting from changes in limb geometry. The selective latency modulation of the proximal muscles with translation direction suggests that the trunk was being actively controlled in all directions. The similar EMG latencies for both narrow and wide stance, with modulation of only the muscle activation magnitude as stance width changed, suggest that the same postural synergy was only slightly modified for a change in stance width. Nevertheless, the magnitude of the trunk displacement, as well as of CoP displacement, was modified based on the degree of passive stiffness in the musculoskeletal system, which increased with stance width. The change from a more passive to an active horizontal force constraint, to larger EMG magnitudes especially in the trunk muscles and larger trunk and CoP excursions in narrow stance are consistent with a more effortful response for equilibrium control in narrow stance to perturbations in all directions.

Henry, S. M.; Fung, J.; Horak, F. B.; Peterson, B. W. (Principal Investigator)



Methods for Exploring Expressive Stance Michael Neff , Eugene Fiume  

E-print Network

adjust our stance relative to that object. Put a large plate of brussel sprouts in front of an average toward brussel sprouts. Similarly, when someone takes interest in an object, he will often orient himself

Neff, Michael


SOCIAL STANCES BY VIRTUAL SMILES Magalie Ochs, Catherine Pelachaud, and Ken Prepin  

E-print Network

characters should then have the capacity to express stances through their verbal and non-verbal behavior. One their interpersonal relationship (called interpersonal stances). The stances can be expressed through non-verbal behaviors, for instance smiles. Stances are also co-constructed by their in- teractants through simultaneous

Pelachaud, Catherine


EMG responses to maintain stance during multidirectional surface translations  

NASA Technical Reports Server (NTRS)

To characterize muscle synergy organization underlying multidirectional control of stance posture, electromyographic activity was recorded from 11 lower limb and trunk muscles of 7 healthy subjects while they were subjected to horizontal surface translations in 12 different, randomly presented directions. The latency and amplitude of muscle responses were quantified for each perturbation direction. Tuning curves for each muscle were examined to relate the amplitude of the muscle response to the direction of surface translation. The latencies of responses for the shank and thigh muscles were constant, regardless of perturbation direction. In contrast, the latencies for another thigh [tensor fascia latae (TFL)] and two trunk muscles [rectus abdominis (RAB) and erector spinae (ESP)] were either early or late, depending on the perturbation direction. These three muscles with direction-specific latencies may play different roles in postural control as prime movers or as stabilizers for different translation directions, depending on the timing of recruitment. Most muscle tuning curves were within one quadrant, having one direction of maximal activity, generally in response to diagonal surface translations. Two trunk muscles (RAB and ESP) and two lower limb muscles (semimembranosus and peroneus longus) had bipolar tuning curves, with two different directions of maximal activity, suggesting that these muscle can play different roles as part of different synergies, depending on translation direction. Muscle tuning curves tended to group into one of three regions in response to 12 different directions of perturbations. Two muscles [rectus femoris (RFM) and TFL] were maximally active in response to lateral surface translations. The remaining muscles clustered into one of two diagonal regions. The diagonal regions corresponded to the two primary directions of active horizontal force vector responses. Two muscles (RFM and adductor longus) were maximally active orthogonal to their predicted direction of maximal activity based on anatomic orientation. Some of the muscles in each of the synergic regions were not anatomic synergists, suggesting a complex central organization for recruitment of muscles. The results suggest that neither a simple reflex mechanism nor a fixed muscle synergy organization is adequate to explain the muscle activation patterns observed in this postural control task. Our results are consistent with a centrally mediated pattern of muscle latencies combined with peripheral influence on muscle magnitude. We suggest that a flexible continuum of muscle synergies that are modifiable in a task-dependent manner be used for equilibrium control in stance.

Henry, S. M.; Fung, J.; Horak, F. B.; Peterson, B. W. (Principal Investigator)



Altered preparatory pelvic control during the sit-to-stance-to-sit movement in people with non-specific low back pain.  


People with non-specific low back pain (LBP) show hampered performance of dynamic tasks such as sit-to-stance-to-sit movement. However, the underlying mechanisms remain obscure. Therefore, the aim of this study was to assess if proprioceptive impairments influence the performance of the sit-to-stance-to-sit movement. First, the proprioceptive steering of 20 healthy subjects and 106 persons with mild LBP was identified during standing using muscle vibration. Second, five sit-to-stance-to-sit repetitions on a stable support and on foam were performed as fast as possible. Total duration, phase duration, center of pressure (COP) displacement, pelvic and thoracic kinematics were analyzed. People with LBP used less lumbar proprioceptive afference for postural control compared to healthy people (P < 0.0001) and needed more time to perform the five repetitions in both postural conditions (P < 0.05). These time differences were determined in the stance and sit phases (transition phases), but not in the focal movement phases. Moreover, later onsets of anterior pelvic rotation initiation were recorded to start both movement sequences (P < 0.05) and to move from sit-to-stance on foam (P < 0.05). Decreased use of lumbar proprioceptive afference in people with LBP seemed to have a negative influence on the sit-to-stance-to-sit performance and more specifically on the transition phases which demand more control (i.e. sit and stance). Furthermore, slower onsets to initiate the pelvis rotation to move from sit-to-stance illustrate a decrease in pelvic preparatory movement in the LBP group. PMID:22595702

Claeys, Kurt; Dankaerts, Wim; Janssens, Lotte; Brumagne, Simon



Coherence analysis of muscle activity during quiet stance  

PubMed Central

Studies of muscle activation during perturbed standing have demonstrated that the typical patterns of coordination (“ankle strategy” and “hip strategy”) are controlled through multiple muscles activated in a distal-to-proximal or proximal-to-distal temporal pattern. In contrast, quiet stance is thought to be maintained primarily through the ankle musculature. Recently, spectral analysis of inter-segment body motion revealed the coexistence of both ankle and hip patterns of coordination during quiet stance, with the predominating pattern dependent on the frequency of body sway. Here we use frequency domain techniques to determine if these patterns are associated with the same muscular patterns as observed during perturbed stance. Six of the seven muscles measured showed a linear relationship to the sway of at least one body segment, all being leg muscles. Muscle–segment phases were consistent with that required to resist gravity at low frequencies, with increasing phase lag as frequency increased. Visual information had effects only at frequencies below 0.5 Hz, where the shift from in-phase to anti-phase trunk–leg co-phase was observed. These results indicate that co-existence of the ankle and hip pattern during quiet stance involves only leg musculature. Anti-phase movement of the trunk relative to the legs at higher frequencies arises from indirect biomechanical control from posterior leg muscles. PMID:17955227

Saffer, Mark; Kiemel, Tim



Situating Reader Stance within and beyond the Efferent-Aesthetic Continuum  

ERIC Educational Resources Information Center

The purpose of this theoretical essay is to encourage critical reflection of the relationship of specific reading events to traditional conceptualizations of reader stance. While conventional models of reader stance are useful for considering many aspects of reading, there are reading events that engender stances that appear to lie outside of the…

Paulson, Eric J.; Armstrong, Sonya L.



Literacy Technologies: What Stance Should We Take?  

Microsoft Academic Search

this article. Although there would be enormousdiVerences as we looked from person to person or across time, we would inevitablysee an array of communication and information technologies in each case,including, perhaps, books, paper and pen, blackboards, overhead transparencies, filing cabinets, index cards, copy machines, scanners, word processors,or Internet. Just listing the technologies in use would tell us something, but notthat

Bertram C. Bruce



Coherence analysis of muscle activity during quiet stance  

Microsoft Academic Search

Studies of muscle activation during perturbed standing have demonstrated that the typical patterns of coordination (“ankle\\u000a strategy” and “hip strategy”) are controlled through multiple muscles activated in a distal-to-proximal or proximal-to-distal\\u000a temporal pattern. In contrast, quiet stance is thought to be maintained primarily through the ankle musculature. Recently,\\u000a spectral analysis of inter-segment body motion revealed the coexistence of both ankle

Mark Saffer; Tim Kiemel; John Jeka



Influence of sprint acceleration stance kinetics on velocity and step kinematics in field sport athletes.  


The interaction between step kinematics and stance kinetics determines sprint velocity. However, the influence that stance kinetics has on effective acceleration in field sport athletes requires clarification. About 25 men (age = 22.4 ± 3.2 years; mass = 82.8 ± 7.2 kg; height = 1.81 ± 0.07 m) completed twelve 10-m sprints, 6 sprints each for kinematic and kinetic assessment. Pearson's correlations (p ? 0.05) examined relationships between 0-5, 5-10, and 0-10 m velocity; step kinematics (mean step length [SL], step frequency, contact time [CT], flight time over each interval); and stance kinetics (relative vertical, horizontal, and resultant force and impulse; resultant force angle; ratio of horizontal to resultant force [RatF] for the first, second, and last contacts within the 10-m sprint). Relationships were found between 0-5, 5-10, and 0-10 m SL and 0-5 and 0-10 m velocity (r = 0.397-0.535). CT of 0-5 and 0-10 m correlated with 5-10 m velocity (r = -0.506 and -0.477, respectively). Last contact vertical force correlated with 5-10 m velocity (r = 0.405). Relationships were established between the second and last contact vertical and resultant force and CT over all intervals (r = -0.398 to 0.569). First and second contact vertical impulse correlated with 0-5 m SL (r = 0.434 and 0.442, respectively). Subjects produced resultant force angles and RatF suitable for horizontal force production. Faster acceleration in field sport athletes involved longer steps, with shorter CT. Greater vertical force production was linked with shorter CT, illustrating efficient force production. Greater SLs during acceleration were facilitated by higher vertical impulse and appropriate horizontal force. Speed training for field sport athletes should be tailored to encourage these technique adaptations. PMID:23222091

Lockie, Robert G; Murphy, Aron J; Schultz, Adrian B; Jeffriess, Matthew D; Callaghan, Samuel J



A robotic cadaveric flatfoot analysis of stance phase.  


The symptomatic flatfoot deformity (pes planus with peri-talar subluxation) can be a debilitating condition. Cadaveric flatfoot models have been employed to study the etiology of the deformity, as well as invasive and noninvasive surgical treatment strategies, by evaluating bone positions. Prior cadaveric flatfoot simulators, however, have not leveraged industrial robotic technologies, which provide several advantages as compared with the previously developed custom fabricated devices. Utilizing a robotic device allows the researcher to experimentally evaluate the flatfoot model at many static instants in the gait cycle, compared with most studies, which model only one to a maximum of three instances. Furthermore, the cadaveric tibia can be statically positioned with more degrees of freedom and with a greater accuracy, and then a custom device typically allows. We created a six degree of freedom robotic cadaveric simulator and used it with a flatfoot model to quantify static bone positions at ten discrete instants over the stance phase of gait. In vivo tibial gait kinematics and ground reaction forces were averaged from ten flatfoot subjects. A fresh frozen cadaveric lower limb was dissected and mounted in the robotic gait simulator (RGS). Biomechanically realistic extrinsic tendon forces, tibial kinematics, and vertical ground reaction forces were applied to the limb. In vitro bone angular position of the tibia, calcaneus, talus, navicular, medial cuneiform, and first metatarsal were recorded between 0% and 90% of stance phase at discrete 10% increments using a retroreflective six-camera motion analysis system. The foot was conditioned flat through ligament attenuation and axial cyclic loading. Post-flat testing was repeated to study the pes planus deformity. Comparison was then made between the pre-flat and post-flat conditions. The RGS was able to recreate ten gait positions of the in vivo pes planus subjects in static increments. The in vitro vertical ground reaction force was within ± 1 standard deviation (SD) of the in vivo data. The in vitro sagittal, coronal, and transverse plane tibial kinematics were almost entirely within ± 1 SD of the in vivo data. The model showed changes consistent with the flexible flatfoot pathology including the collapse of the medial arch and abduction of the forefoot, despite unexpected hindfoot inversion. Unlike previous static flatfoot models that use simplified tibial degrees of freedom to characterize only the midpoint of the stance phase or at most three gait positions, our simulator represented the stance phase of gait with ten discrete positions and with six tibial degrees of freedom. This system has the potential to replicate foot function to permit both noninvasive and surgical treatment evaluations throughout the stance phase of gait, perhaps eliciting unknown advantages or disadvantages of these treatments at other points in the gait cycle. PMID:21599096

Jackson, Lyle T; Aubin, Patrick M; Cowley, Matthew S; Sangeorzan, Bruce J; Ledoux, William R



How Joint Torques Affect Hamstring Injury Risk in Sprinting Swing–Stance Transition  

PubMed Central

ABSTRACT Purpose The potential mechanisms of hamstring strain injuries in athletes are not well understood. The study, therefore, was aimed at understanding hamstring mechanics by studying loading conditions during maximum-effort overground sprinting. Methods Three-dimensional kinematics and ground reaction force data were collected from eight elite male sprinters sprinting at their maximum effort. Maximal isometric torques of the hip and knee were also collected. Data from the sprinting gait cycle were analyzed via an intersegmental dynamics approach, and the different joint torque components were calculated. Results During the initial stance phase, the ground reaction force passed anteriorly to the knee and hip, producing an extension torque at the knee and a flexion torque at the hip joint. Thus, the active muscle torque functioned to produce flexion torque at the knee and extension torque at the hip. The maximal muscle torque at the knee joint was 1.4 times the maximal isometric knee flexion torque. During the late swing phase, the muscle torque counterbalanced the motion-dependent torque and acted to flex the knee joint and extend the hip joint. The loading conditions on the hamstring muscles were similar to those of the initial stance phase. Conclusions During both the initial stance and late swing phases, the large passive torques at both the knee and hip joints acted to lengthen the hamstring muscles. The active muscle torques generated mainly by the hamstrings functioned to counteract those passive effects. As a result, during sprinting or high-speed locomotion, the hamstring muscles may be more susceptible to high risk of strain injury during these two phases. PMID:24911288




The influence of ankle muscle activation on postural sway during quiet stance.  


Although balance during quiet standing is postulated to be influenced by multiple factors, including ankle stiffness, it is unclear how different mechanisms underlying increases in stiffness affect balance control. Accordingly, this study examined the influence of muscle activation and passive ankle stiffness increases on the magnitude and frequency of postural sway. Sixteen young adults participated in six quiet stance conditions including: relaxed standing, four muscle active conditions (10%, 20%, 30% and 40% maximum voluntary contraction (MVC)), and one passive condition wearing an ankle foot orthotic (AFO). Kinetics were collected from a force plate, while whole-body kinematics were collected with a 12-sensor motion capture system. Bilateral electromyographic signals were recorded from the tibialis anterior and medial gastrocnemius muscles. Quiet stance sway amplitude (range and root mean square) and frequency (mean frequency and velocity) in the sagittal plane were calculated from time-varying centre of gravity (COG) and centre of pressure (COP) data. Compared to the relaxed standing condition, metrics of sway amplitude were significantly increased (between 37.5 and 63.2%) at muscle activation levels of 30% and 40% MVC. Similarly, frequency measures increased between 30.5 and 154.2% in the 20-40% MVC conditions. In contrast, passive ankle stiffness, induced through the AFO, significantly decreased sway amplitude (by 23-26%), decreased COG velocity by 13.8%, and increased mean COP frequency by 24.9%. These results demonstrate that active co-contraction of ankle musculature (common in Parkinson's Disease patients) may have differential effects on quiet stance balance control compared to the use of an ankle foot orthotic (common for those recovering from stroke). PMID:24613374

Warnica, Meagan J; Weaver, Tyler B; Prentice, Stephen D; Laing, Andrew C



Use of wavelet coherence to assess two-joint coordination during quiet upright stance.  


Joint coordination plays a critical role in maintaining postural stability, yet there is limited existing work describing joint coordination patterns in the time-frequency domain. Here, two-joint coordination was examined during quiet upright stance. A wavelet coherence method was applied to quantify the coherence between ankle-trunk and ankle-head angles in the sagittal and frontal planes. Wavelet coherence results indicated intermittent joint coordination particularly for frequencies of 2.5-4.0Hz. Coherence results were further processed to estimate mean time intervals between coherence instances, coherence burst frequency, and the ratio of in-phase versus anti-phase behaviors. Time intervals between intermittent coherence were 1.3-1.5sec, coherence burst frequency was ~0.4Hz, and phase ratios were ~1.0. Intermittent "bursting" of postural muscles may account for the finding of intermittent coherence in the noted frequency band. Some age and/or gender differences in coherence were found, and may be related to comparable differences in postural control ability or strategies. Results from application of this new method support earlier evidence that kinematic coordination is achieved intermittently rather than continuously during quiet upright stance. This method may provide richer information regarding such coordination, and could be a useful approach in future studies. PMID:25073748

Zhang, Hongbo; Nussbaum, Maury A; Agnew, Michael J



Eldecalcitol improves chair-rising time in postmenopausal osteoporotic women treated with bisphosphonates  

PubMed Central

An open-label randomized controlled trial was conducted to clarify the effect of eldecalcitol (ED) on body balance and muscle power in postmenopausal osteoporotic women treated with bisphosphonates. A total of 106 postmenopausal women with osteoporosis (mean age 70.8 years) were randomly divided into two groups (n=53 in each group): a bisphosphonate group (control group) and a bisphosphonate plus ED group (ED group). Biochemical markers, unipedal standing time (body balance), and five-repetition chair-rising time (muscle power) were evaluated. The duration of the study was 6 months. Ninety-six women who completed the trial were included in the subsequent analyses. At baseline, the age, body mass index, bone mass indices, bone turnover markers, unipedal standing time, and chair-rising time did not differ significantly between the two groups. During the 6-month treatment period, bone turnover markers decreased significantly from the baseline values similarly in the two groups. Although no significant improvement in the unipedal standing time was seen in the ED group, compared with the control group, the chair-rising time decreased significantly in the ED group compared with the control group. The present study showed that ED improved the chair-rising time in terms of muscle power in postmenopausal osteoporotic women treated with bisphosphonates. PMID:24476669

Iwamoto, Jun; Sato, Yoshihiro



Stability and the maintenance of balance following a perturbation from quiet stance  

NASA Astrophysics Data System (ADS)

We investigate stability and the maintenance of balance with the use of tools from dynamical systems. In particular we investigate the application of such tools to the study of the ground reaction forces resulting from an athlete being perturbed from quiet stance. We develop a nonlinear model consisting of a set of coupled vector fields for the derivative with respect to time of the angles between the resultant ground reaction forces and the vertical in the anteroposterior and mediolateral directions. This model contains a basin of attraction bound by a closed curve which we call the critical curve. It is only inside this curve that perturbations can be corrected, with the orbit spiraling onto an attractor corresponding to quiet stance. We show how the critical curve and also the strength of the attractor found in the basin of attraction can be fit to model the experimental data (time series) for an individual athlete. We also discuss how our model can be used to identify nonsymmetric behavior caused by muscle imbalances and differences in the ranges of motion on either side of the body.

Stirling, J. R.; Zakynthinaki, M. S.



Climate Literacy for Kids: Finding Medium, Message, and Stance  

NASA Astrophysics Data System (ADS)

As part of NASA's Global Climate Change ( website (winner of the 2011Webby Award for Best Science Site), Climate Kids ( presents positive role models for green careers and encourages kids to be good climate citizens. But before they will care, they must understand. Climate Kids helps kids understand climate science by communicating at their own science awareness and maturity level, and by giving them concrete ways to start helping Earth now. Climate Kids, as informal education, speaks to upper-elementary-school-age kids in their own language and using some of their favorite media. In addition to simple, liberally illustrated text explanations of the basic science concepts, cartoons and games reinforce the concepts in a fun way. A growing section on green careers interviews enthusiastic individuals currently practicing their professions. In explaining what they do, these individuals reinforce the climate science concepts and "how to help" suggestions elsewhere on the site. The games also reinforce the green career choices. "Green Careers" currently features a "green" general contractor, a home energy auditor, a water-wise landscaper, a recycling program educator, and a renewable energy scientist. The message of the scientist, who designs wind energy farms and "architectural wind" arrays, is reinforced by the "Power-up" game. In this game, players move a wind turbine up or down to capture the wind and move a solar array back and forth to stay out of cloud shadows. Depending on how many "windows" of the game's "city" light up using these alternative energy sources, the player earns a bronze, silver, gold, or platinum "medal." A recycling game reinforces the messages of the recycling program educator about the importance of recycling in saving energy, what can and cannot be recycled, and how long trash items remain in a landfill before decomposing. In the game, a variety of throw-away objects rains down from the top of the screen. Various recycling bins (glass, plastic, metal, and paper) are lined up on the left and right sides of the screen, with a trash bin at the bottom. As an item drops, the player must quickly decide what kind of material it is made of and whether it is recyclable, then guide it into the appropriate bin. As the rate of items entering play increases, any missed items fall into the trash and stay there for a length of time proportional to their decomposition time. If the trash bin gets full, the game is over. While enjoying the increasing challenge of the game, players learn to identify many items as recyclable that they may not have recognized as recyclable before. Another feature on Climate Kids is "Climate Tales," a slightly edgy animated cartoon series (two episodes so far) about the adventures of a blundering polar bear, a chirpy tamarin monkey, and a grumpy old fish as "accidental tourists" around the planet, observing and dealing with the environmental conditions they encounter. Fairly complex concepts (such as reasons and implications of the declining abundance of phytoplankton) are woven into the tales. Climate Kids is a fun site for kids, educational and realistic, and yet positive and hopeful-the only reasonable stance to present to this young audience.

Fisher, D. K.; Leon, N.; Jackson, R.; Greene, M. P.



Stance-phase force on the opposite limb dictates swing-phase afferent presynaptic inhibition during locomotion  

PubMed Central

Presynaptic inhibition is a powerful mechanism for selectively and dynamically gating sensory inputs entering the spinal cord. We investigated how hindlimb mechanics influence presynaptic inhibition during locomotion using pioneering approaches in an in vitro spinal cord–hindlimb preparation. We recorded lumbar dorsal root potentials to measure primary afferent depolarization-mediated presynaptic inhibition and compared their dependence on hindlimb endpoint forces, motor output, and joint kinematics. We found that stance-phase force on the opposite limb, particularly at toe contact, strongly influenced the magnitude and timing of afferent presynaptic inhibition in the swinging limb. Presynaptic inhibition increased in proportion to opposite limb force, as well as locomotor frequency. This form of presynaptic inhibition binds the sensorimotor states of the two limbs, adjusting sensory inflow to the swing limb based on forces generated by the stance limb. Functionally, it may serve to adjust swing-phase sensory transmission based on locomotor task, speed, and step-to-step environmental perturbations. PMID:22442562

Hayes, Heather Brant; Chang, Young-Hui



A Cross-Cultural Analysis of Stance in Disaster News Reports  

ERIC Educational Resources Information Center

This study examines stance in cross-cultural media discourse by comparing disaster news reports on the Sichuan earthquake of May 2008 in a Chinese, an Australian Chinese, and an Australian newspaper. The stance taken in the news reports is examined using the Attitude sub-system of Martin and White's (2005) Appraisal framework. The analysis…

Liu, Lian; Stevenson, Marie



Exploring Valued Patterns of Stance in Upper-Level Student Writing in the Disciplines  

ERIC Educational Resources Information Center

Drawing on the appraisal framework from systemic functional linguistics (SFL), this article examines patterns of stance in a corpus of 92 high- and low-graded argumentative papers written in the context of an upper-level course in economics. It interprets differential patterns of stance in students' texts in light of interview commentaries…

Lancaster, Zak



Linguistic Markers of Stance in Early and Advanced Academic Writing: A Corpus-Based Comparison  

ERIC Educational Resources Information Center

This article uses corpus methods to examine linguistic expressions of stance in over 4,000 argumentative essays written by incoming first-year university students in comparison with the writing of upper-level undergraduate students and published academics. The findings reveal linguistic stance markers shared across the first-year essays despite…

Aull, Laura L.; Lancaster, Zak



Signaling Organization and Stance: Academic Language Use in Middle Grade Persuasive Writing  

ERIC Educational Resources Information Center

Effective academic writing is accessible to readers because writers follow shared conventions for organization and signal their stance on particular topics; however, few specifics are known about how middle graders might develop knowledge of and use these academic language forms and functions to signal their organization and stance in persuasive…

Dobbs, Christina L.



Modulation of tibialis anterior muscle activity changes with upright stance width.  


When individuals stand with their feet apart, activation of tibialis anterior (TA) muscle seems to slightly exceed rest levels. In narrow stances, conversely, the stabilization of body lateral sways may impose marked, active demand on ankle inversors/eversors. In this study we investigate how much the modulation in TA activity, associated to center of pressure (COP) lateral sways, changes when stance width reduces. Surface EMG and COP coordinates were collected from 17 subjects at three different stances: feet apart, feet together and tandem. Pearson correlation analysis was applied to check whether the expected greater modulations in TA activity corresponded to a stronger association between fluctuations in EMG amplitude and COP lateral sways. When standing at progressively narrower stances participants showed larger fluctuations in COP lateral sways (p<0.01) and higher EMG-COP association (p<0.01); marked increases in TA activity were only observed in tandem stance (p<0.001). Interestingly, more pronounced modulations in TA activity were observed for subjects showing greater association between EMG amplitude and COP sways in feet together and tandem stance (Pearson R>0.56, p<0.02), though not when standing with feet apart (R=-0.22, p=0.40). These results indicate that the contribution of TA activity to lateral sway control increases for narrower stances. PMID:25156446

Lemos, Thiago; Imbiriba, Luís A; Vargas, Claudia D; Vieira, Taian M



Influence of voluntary teeth clenching on the stabilization of postural stance disturbed by electrical stimulation of unilateral lower limb.  


Studies on the relationship between dental occlusion and body balance have suggested that occlusion status contributes to the maintenance of postural balance. However, little has been reported about the effects of voluntary teeth clenching on the stabilization of postural stance in novel environments. In the present study we investigated whether teeth clenching influenced adaptation to the perturbation introduced by electrical stimulation of a unilateral lower limb. Subjects (12 adults) stood on a force plate, from which motion data were obtained in the horizontal plane with and without voluntary teeth clenching and were instructed to maintain the position throughout the experiment. We evoked a novel environment by supramaximal percutaneous electrical stimulation of the common peroneal nerve. Electromyograms (EMG) were recorded from the masseter and the peroneus longus (PL) muscles with bipolar surface cup electrodes. When the disturbed postural stance was generated by electrical stimulation, the maximum reaction force in the anterior-posterior (A/P) direction with teeth clenching (CL) was significantly smaller than that without voluntary teeth clenching (control; CO) (p<0.05) and the peak time of the ground reaction force/body mass (GRF/BM) in the A/P direction occurred earlier in the CL condition than CO (p<0.05). There were no significant differences in the peak-to-peak amplitude of GRF/BM and the peak time of GRF/BM, in the M/L direction under both CL and CO conditions. Thus, the present study showed that voluntary teeth clenching contributed to stabilization of the postural stance perturbed transiently by electrical stimulation. We concluded that voluntary teeth clenching plays an important role in rapid postural adaptation to the anterior-posterior perturbation in the upright position. PMID:19879763

Fujino, Sachiko; Takahashi, Toshiyuki; Ueno, Toshiaki



SEEK Web tutor: fostering a critical stance while exploring the causes of volcanic eruption  

Microsoft Academic Search

We investigated the impact of a Web tutor on college students’ critical stance and learning while exploring Web pages on science.\\u000a Critical stance is an aspect of self-regulated learning that emphasizes the need to evaluate the truth and relevance of information\\u000a as the learner engages in systematic inquiry to answer challenging questions. The Web tutor is called SEEK, an acronym

Arthur C. Graesser; Jennifer Wiley; Susan R. Goldman; Tenaha O’Reilly; Moongee Jeon; Bethany McDaniel



The Single-Leg-Stance Test in Parkinson’s Disease  

PubMed Central

Background Timed single-leg-stance test (SLST) is widely used to assess postural control in the elderly. In Parkinson’s disease (PD), it has been shown that an SLST around 10 seconds or below may be a sensitive indicator of future falls. However, despite its role in fall risk, whether SLST times around 10 seconds marks a clinically important stage of disease progression has largely remained unexplored. Methods A cross-sectional study where 27 people with PD were recruited and instructed to undertake timed SLST for both legs was conducted. Disease motor impairment was assessed with the Unified Parkinson’s Disease Rating Scale Part 3 (UPDRS-III). Results This study found that: 1) the SLST in people with PD shows good test-retest reliability; 2) SLST values can be attributed to two non-overlapping clusters: a low (10.4 ± 6.3 seconds) and a high (47.6 ± 11.7 seconds) value SLST group; 3) only the low value SLST group can be considered abnormal when age-matched normative SLST data are taken into account for comparison; and 4) lower UPDRS-III motor performance, and the bradykinesia sub-score in particular, are only associated with the low SLST group. Conclusion These results lend further support that a low SLST time around 10 seconds marks a clinically important stage of disease progression with significant worsening of postural stability in PD. PMID:25584104

Chomiak, Taylor; Pereira, Fernando Vieira; Hu, Bin



Walking with wider steps increases stance phase gluteus medius activity.  


Increases in step width have been reported for several clinical populations, including older adults and stroke survivors. These populations often also exhibit decreased hip abductor strength, suggesting that walking with wider steps may be an adaptive response in order to reduce the mechanical demands on the hip abductors. The purpose of this study was to quantify the relationship between step width and gluteus medius (GM) activity during walking. Fourteen young, uninjured adults walked on a treadmill at 1.25m/s for four step width conditions (Normal, Narrow, Medium, and Wide) while step width and stance phase GM electromyographic (EMG) activity were quantified. We also measured hip abduction torque and GM activity during maximum voluntary isometric contractions (MVICs) at three hip angles (neutral, abducted 10°, and abducted 20°). During walking trials, GM activity was significantly (p<0.0001) influenced by step width; compared to Normal walking, GM activity was 47% higher with Wide steps and 24% lower with Narrow steps. We also observed a weak positive correlation (r=0.18±0.14) between step width and GM activity during Normal walking, as GM activity was higher with wider steps. These results cannot be attributed to changes in GM conformation under the recording electrode, as GM activity was not influenced by hip angle during MVICs. The increased GM activity with wider steps does not support the proposal that increasing step width would be a beneficial adaptation to weakened hip abductors. A likely alternative explanation is that increased step width is a response to decreased gait balance. PMID:25300241

Kubinski, Samantha N; McQueen, Christina A; Sittloh, Keir A; Dean, Jesse C



Development of a mechatronic platform and validation of methods for estimating ankle stiffness during the stance phase of walking.  


The mechanical properties of human joints (i.e., impedance) are constantly modulated to precisely govern human interaction with the environment. The estimation of these properties requires the displacement of the joint from its intended motion and a subsequent analysis to determine the relationship between the imposed perturbation and the resultant joint torque. There has been much investigation into the estimation of upper-extremity joint impedance during dynamic activities, yet the estimation of ankle impedance during walking has remained a challenge. This estimation is important for understanding how the mechanical properties of the human ankle are modulated during locomotion, and how those properties can be replicated in artificial prostheses designed to restore natural movement control. Here, we introduce a mechatronic platform designed to address the challenge of estimating the stiffness component of ankle impedance during walking, where stiffness denotes the static component of impedance. The system consists of a single degree of freedom mechatronic platform that is capable of perturbing the ankle during the stance phase of walking and measuring the response torque. Additionally, we estimate the platform's intrinsic inertial impedance using parallel linear filters and present a set of methods for estimating the impedance of the ankle from walking data. The methods were validated by comparing the experimentally determined estimates for the stiffness of a prosthetic foot to those measured from an independent testing machine. The parallel filters accurately estimated the mechatronic platform's inertial impedance, accounting for 96% of the variance, when averaged across channels and trials. Furthermore, our measurement system was found to yield reliable estimates of stiffness, which had an average error of only 5.4% (standard deviation: 0.7%) when measured at three time points within the stance phase of locomotion, and compared to the independently determined stiffness values of the prosthetic foot. The mechatronic system and methods proposed in this study are capable of accurately estimating ankle stiffness during the foot-flat region of stance phase. Future work will focus on the implementation of this validated system in estimating human ankle impedance during the stance phase of walking. PMID:23719922

Rouse, Elliott J; Hargrove, Levi J; Perreault, Eric J; Peshkin, Michael A; Kuiken, Todd A



In vivo length patterns of the medial collateral ligament during the stance phase of gait  

PubMed Central

Purpose The function of the medial collateral ligament (MCL) during gait has not been investigated. Our objective was to measure the kinematics of the medial collateral ligament during the stance phase of gait on a treadmill using a combined dual fluoroscopic imaging system (DFIS) and MRI technique. Methods Three-dimensional models of the knee were constructed using magnetic resonance images of 7 healthy human knees. The contours of insertion areas of the superficial MCL (sMCL) and deep MCL (dMCL) on the femur and tibia were constructed using the coronal plane MR images of each knee. Both the sMCL and the dMCL were separated into 3 portions: the anterior, mid, and posterior bundles. The relative elongation of the bundles was calculated using the bundle length at heel strike (or 0% of the stance phase) as a reference. Results The lengths of the anterior bundles were positively correlated with the knee flexion angle. The mid-bundles of the sMCL and dMCL were found to function similarly in trend with the anterior bundles during the stance phase of the gait and their lengths had weak correlations with the knee flexion angles. The elongations of the posterior bundles of sMCL and dMCL were peaked at mid-stance and terminal extension/pre-swing stance phase. The lengths of the posterior bundles were negatively correlated with the knee flexion during the stance phase. Conclusion The data of this study demonstrated that the anterior and posterior bundles of the sMCL and dMCL have a reciprocal function during the stance phase of gait. This data provide insight into the function of the MCL and a normal reference for the study of physiology and pathology of the MCL. The data may be useful in designing reconstruction techniques to better reproduce the native biomechanical behavior of the MCL. Level of evidence IV. PMID:21153541

Liu, Fang; Gadikota, Hemanth R.; Kozánek, Michal; Hosseini, Ali; Yue, Bing; Gill, Thomas J.; Rubash, Harry E.; Li, Guoan



EFL Doctoral Students' Conceptions of Authorial Stance in Academic Knowledge Claims and the Tie to Epistemic Beliefs  

ERIC Educational Resources Information Center

Taking an effective authorial stance in research argumentation has been designated as both vitally important and challenging. The study investigated English as a foreign language (EFL) doctoral students' conceptions of authorial stance, the role of domains in affecting their conceptions, and the ties of the conceptions to the…

Chang, Peichin; Tsai, Chin-Chung



Epistemological and Interpersonal Stance in a Data Description Task: Findings from a Discipline-Specific Learner Corpus  

ERIC Educational Resources Information Center

This article examines the stance options used by writers responding to a data description task in the discipline of Statistics. Based on a small learner corpus, it uses inductive qualitative content analysis to explore both the content propositions that students included in their writing, and the ways in which they expressed evaluative stance

Wharton, Sue



Ethical Considerations for Psychologists Taking a Public Stance on Controversial Issues: The Balance Between Personal and Professional Life  

PubMed Central

Previous literature has documented the general issues psychologists often face while balancing their personal and professional lives. The struggle stems from attempting to satisfy the need to maintain a life outside of work while having the professional obligation to follow the American Psychological Association’s (APA’s) Ethical Principles of Psychologists and Code of Conduct (Ethics Code) to prevent their personal lives from interfering with their professional roles and relationships. The present paper analyzes the subject of psychologists taking a public position on controversial public issues. Although the APA Ethics Code does not restrict how psychologists conduct themselves during their personal time, taking a public stance on a controversial issue could potentially strain professional relationships and inadvertently reflect negatively on the profession. The present paper examines ethical issues that a) should be taken into account before psychologists take a public position on a controversial issue, and b) are in conflict with APA’s Ethics Code or current research. PMID:25342876

Haeny, Angela M.



Pedunculopontine ucleus Area Oscillations during Stance, Stepping and Freezing in Parkinson's Disease  

E-print Network

, and stance in seven Parkinson's disease patients who received bilateral PPNa implantation for disabling of the PPNa in the regulation of gait and suggest that, in Parkinson disease, gait difficulties could in Parkinson's Disease. PLoS ONE 8(12): e83919. doi:10.1371/journal.pone.0083919 Editor: Mathias Toft, Oslo

Paris-Sud XI, Université de


Visual control of human stance on a narrow and soft support surface.  


The influence of additional visual feedback (VF) on stance control was studied under conditions of changed afferent information from the foot sole and ankle joint due to different support surfaces. The changes of body sway amplitudes were analyzed and their frequency spectrum was established. The effect of visual feedback on the amplitude and frequency characteristics of human stance was manifested as: a) a decrease of the mean amplitude of body sway during visual feedback, corresponding to the decrease of power spectrum density (PSD) of stabilograms in the frequency range below 0.05 Hz, b) an increase of mean velocity of body sway corresponding to the increase of PSD of stabilograms in the frequency range of 0.4-1.5 Hz. The results showed that the improvement of the upright stance by additional visual feedback is mainly mediated through activation of postural muscles at the ankle level, or ankle strategy. The stabilization effect of VF on stance control is slight or negligible if the performance part in ankle joint (narrow support) was reduced. PMID:8280726

Krizková, M; Hlavacka, F; Gatev, P



Stance and Engagement in Pure Mathematics Research Articles: Linking Discourse Features to Disciplinary Practices  

ERIC Educational Resources Information Center

Recent ESP research into academic writing has shown how writers convey their stance and interact with readers across different disciplines. However, little research has been carried out into the disciplinary writing practices of the pure mathematics academic community from an ESP genre analysis perspective. This study begins to address this gap by…

McGrath, Lisa; Kuteeva, Maria



Balance control during an arm raising movement in bipedal stance: which biomechanical factor is controlled?  

Microsoft Academic Search

In order to obtain new insight into the control of balance during arm raising movements in bipedal stance, we performed a biomechanical analysis of kinematics and dynamical aspects of arm raising movements by combining experimental work, large-scale models of the body, and techniques simulating human behavior. A comparison between experimental and simulated joint kinematics showed that the minimum torque change

Myriam Ferry; Luc Martin; Nicolas Termoz; Julie Côté; Francois Prince



J's Epistemological Stance and Strategies To appear in Intentional Conceptual Change, G. Sinatra &  

E-print Network

J's Epistemological Stance and Strategies To appear in Intentional Conceptual Change, G. Sinatra as "intuitive epistemology," what people know about knowledge, knowing, and learning, as acquired from their experiences in everyday life and in school. The study of students' epistemological ideas has become

Elby, Andy


In vivo tibiofemoral cartilage deformation during the stance phase of gait.  


The knowledge of articular cartilage contact biomechanics in the knee joint is important for understanding the joint function and cartilage pathology. However, the in vivo tibiofemoral articular cartilage contact biomechanics during gait remains unknown. The objective of this study was to determine the in vivo tibiofemoral cartilage contact biomechanics during the stance phase of treadmill gait. Eight healthy knees were magnetic resonance (MR) scanned and imaged with a dual fluoroscopic system during gait on a treadmill. The tibia, femur and associated cartilage were constructed from the MR images and combined with the dual fluoroscopic images to determine in vivo cartilage contact deformation during the stance phase of gait. Throughout the stance phase of gait, the magnitude of peak compartmental contact deformation ranged between 7% and 23% of the resting cartilage thickness and occurred at regions with thicker cartilage. Its excursions in the anteroposterior direction were greater in the medial tibiofemoral compartment as compared to those in the lateral compartment. The contact areas throughout the stance phase were greater in the medial compartment than in the lateral compartment. The information on in vivo tibiofemoral cartilage contact biomechanics during gait could be used to provide physiological boundaries for in vitro testing of cartilage. Also, the data on location and magnitude of deformation among non-diseased knees during gait could identify where loading and later injury might occur in diseased knees. PMID:19896131

Liu, Fang; Kozanek, Michal; Hosseini, Ali; Van de Velde, Samuel K; Gill, Thomas J; Rubash, Harry E; Li, Guoan



Dynamic transitions in stance support accompanying leg flexion movements in man  

Microsoft Academic Search

The control processes underlying dynamic transitions in stance support during single leg flexion movements were investigated in human subjects as a function of the intended speed of movement, by examining the vertical and lateral horizontal components of the ground reaction forces, the frontal plane trajectory of the body center of mass (CM) recorded via motion analysis, and the electromyographic (EMG)

M. W. Rogers; Yi-Chung Pai



Turkish Language Teachers' Stance Taking Movements in the Discourse on Globalization and Language  

ERIC Educational Resources Information Center

This study investigates how Turkish teachers take and give stances in the discourse on globalization and language by using linguistic resources. According to the findings obtained through the discourse analysis of the corpus that consisted of 36 h of recording of the discussion among 4 teachers with 5 to 10 years of teaching experience, the…

Coskun, Ibrahim



A biomechanical model to determine lumbosacral loads during single stance phase in normal gait  

Microsoft Academic Search

A dynamic biomechanical model to determine loads (joint forces) attained at the lumbosacral joint-centre during the stance phase of normal level walking was developed. The biomechanical model was based on rigid free body-segments; namely, the foot, shank, thigh, pelvis and head, arms and trunk (HAT) segments. In this biomechanical model, the forces and moments acting on the lumbar spine are

B. C. C. Khoo; J. C. H. Goh; K. Bose



Bone contact forces on the distal tibia during the stance phase of running  

Microsoft Academic Search

Although the tibia is a common site of stress fractures in runners, the loading of the tibia during running is not well understood. An integrated experimental and modeling approach was therefore used to estimate the bone contact forces acting on the distal end of the tibia during the stance phase of running, and the contributions of external and internal sources

Siriporn Sasimontonkul; Brian K. Bay; Michael J. Pavol



Reported Thought as a Stance-Taking Device in Korean Conversation  

ERIC Educational Resources Information Center

Analyses of 34 cases of direct reported thought found in ordinary Korean conversations illustrate a routine practice in the use of reported thought-reenacting a prior thought to demonstrate how the speaker's current stance originated. Often, such thoughts are not simply momentary, isolated thoughts in passing but are consequential thoughts…

Kim, Mary Shin



HRD Attitudes: Or the Roles and Ethical Stances of Human Resource Developers  

Microsoft Academic Search

The paper challenges the assumption that HRD practice is necessarily good or benign. It recognizes that HRD involves moral choices and provides a conceptual exploration of the matter, enlivened by anecdotal illustration. The semiotic square is the chosen tool for the task. It has been built around a descriptive matrix of HRD roles and four ethical stances. All the roles

Colin Fisher



Divergent Effects of Cognitive Load on Quiet Stance and Task-Linked Postural Coordination  

ERIC Educational Resources Information Center

Performing a cognitive task while maintaining upright stance can lead to increased or reduced body sway depending on tasks and experimental conditions. Because greater sway is commonly taken to indicate loosened postural control, and vice versa, the precise impact of cognitive load on postural stability has remained unclear. In much of the large…

Mitra, Suvobrata; Knight, Alec; Munn, Alexandra



Dominant side in single-leg stance stability during floor oscillations at various frequencies  

PubMed Central

Background We investigated lateral dominance in the postural stability of single-leg stance with anteroposterior floor oscillations at various frequencies. Methods Thirty adults maintained a single-leg stance on a force platform for 20 seconds per trial. Trials were performed with no oscillation (static condition) and with anteroposterior floor oscillations (2.5-cm amplitude) at six frequencies: 0.25, 0.5, 0.75, 1.0, 1.25 and 1.5 Hz (dynamic condition). A set of three trials was performed on each leg in each oscillation frequency in random order. The mean speed of the center of pressure in the anteroposterior direction (CoPap) was calculated as an index of postural stability, and frequency analysis of CoPap sway was performed. Footedness for carrying out mobilizing activities was assessed with a questionnaire. Results CoPap speed exponentially increased as oscillation frequency increased in both legs. The frequency analysis of CoPap showed a peak <0.3 Hz at no oscillation. The frequency components at 0.25-Hz oscillation included common components with no oscillation and those at 1.5-Hz oscillation showed the maximum amplitude among all conditions. Postural stability showed no significant difference between left- and right-leg stance at no oscillation and oscillations ?1.25 Hz, but at 1.5-Hz oscillation was significantly higher in the right-leg stance than in the left-leg stance. For the lateral dominance of postural stability at individual levels, the lateral difference in postural stability at no oscillation was positively correlated with that at 0.25-Hz oscillation (r?=?0.51) and negatively correlated with that at 1.5-Hz oscillation (r?=?-0.53). For 70% of subjects, the dominant side of postural stability was different at no oscillation and 1.5-Hz oscillation. In the subjects with left- or right-side dominance at no oscillation, 94% or 38% changed their dominant side at 1.5-Hz oscillation, with a significant difference between these percentages. In the 1.5-Hz oscillation, 73% of subjects had concordance between the dominant side of postural stability and that of mobilizing footedness. Conclusion In static conditions, there was no lateral dominance of stability during single-leg stance. At 1.5-Hz oscillation, the highest frequency, right-side dominance of postural stability was recognized. Functional role in supporting leg may be divided between left and right legs according to the change of balance condition from static to dynamic. PMID:25127541



Speaking "Common Sense" about the Soviet Threat: Reagan's Rhetorical Stance.  

ERIC Educational Resources Information Center

Although for the 15 years preceding his election as President of the United States Ronald Reagan muted his anti-Soviet rhetoric in order to achieve political power, since his election he has returned to anti-Sovietism in an effort to redirect American foreign policy against the Soviets. At the same time, however, he employs a rhetorical strategy…

Ivie, Robert L.


Dependence of joint stiffness on the conditions of visual control in upright undisturbed stance in humans  

Microsoft Academic Search

We recorded the sagittal and frontal components of the stabilogram of healthy humans in upright undisturbed stance under five\\u000a conditions of visual control: (i) open eyes (OE); (ii) closed eyes (CE); (iii) visual inversion (VI); (iv) central vision\\u000a (CV), and (v) diffused light (DL). Through a low-pass filter of trajectories of the center of pressure of feet (CPF), the\\u000a vertical

B. N. Smetanin; K. E. Popov; G. V. Kozhina



Postural Instability Detection: Aging and the Complexity of Spatial-Temporal Distributional Patterns for Virtually Contacting the Stability Boundary in Human Stance  

PubMed Central

Falls among the older population can severely restrict their functional mobility and even cause death. Therefore, it is crucial to understand the mechanisms and conditions that cause falls, for which it is important to develop a predictive model of falls. One critical quantity for postural instability detection and prediction is the instantaneous stability of quiet upright stance based on motion data. However, well-established measures in the field of motor control that quantify overall postural stability using center-of-pressure (COP) or center-of-mass (COM) fluctuations are inadequate predictors of instantaneous stability. For this reason, 2D COP/COM virtual-time-to-contact (VTC) is investigated to detect the postural stability deficits of healthy older people compared to young adults. VTC predicts the temporal safety margin to the functional stability boundary (?=? limits of the region of feasible COP or COM displacement) and, therefore, provides an index of the risk of losing postural stability. The spatial directions with increased instability were also determined using quantities of VTC that have not previously been considered. Further, Lempel-Ziv-Complexity (LZC), a measure suitable for on-line monitoring of stability/instability, was applied to explore the temporal structure or complexity of VTC and the predictability of future postural instability based on previous behavior. These features were examined as a function of age, vision and different load weighting on the legs. The primary findings showed that for old adults the stability boundary was contracted and VTC reduced. Furthermore, the complexity decreased with aging and the direction with highest postural instability also changed in aging compared to the young adults. The findings reveal the sensitivity of the time dependent properties of 2D VTC to the detection of postural instability in aging, availability of visual information and postural stance and potential applicability as a predictive model of postural instability during upright stance. PMID:25295589

Kilby, Melissa C.; Slobounov, Semyon M.; Newell, Karl M.



Unilateral Stance Strategies of Athletes With ACL Deficiency  

PubMed Central

Aberrant movement strategies are characteristic of ACL-deficient athletes with recurrent knee instability (non-copers), and may instigate premature or accelerate joint degradation. Biomechanical evaluation of kinematic changes over time may elucidate noncopers’ responses to neuromuscular intervention and ACL reconstruction (ACLR). Forty noncopers were randomized into a perturbation group or a strength training only group. We evaluated the effects of perturbation training, and then gender on knee angle and tibial position during a unilateral standing task before and after ACLR. No statistically significant interactions were found. Before surgery, the strength training only group demonstrated knee angle asymmetry, but 6 months after ACLR, both groups presented with similar knee flexion between limbs. Aberrant and asymmetrical tibial position was found only in females following injury and ACLR. Neither treatment group showed distinct unilateral standing strategies following intervention; however, males and female noncopers appear to respond uniquely to physical therapy and surgery. PMID:22983931

Di Stasi, Stephanie L.; Hartigan, Erin H.; Snyder-Mackler, Lynn



From relational ontology to transformative activist stance on development and learning: expanding Vygotsky's (CHAT) project  

NASA Astrophysics Data System (ADS)

This paper offers steps towards overcoming current fragmentation within sociocultural approaches by expansively reconstructing a broad dialectical view on human development and learning (drawing on Vygotsky's project) underwritten by ideology of social justice. The common foundation for sociocultural approaches is developed by dialectically supplanting relational ontology with the notion that collaborative purposeful transformation of the world is the core of human nature and the principled grounding for learning and development. An activist transformative stance suggests that people come to know themselves and their world as well as ultimately come to be human in and through (not in addition to) the processes of collaboratively transforming the world in view of their goals. This means that all human activities (including psychological processes and the self) are instantiations of contributions to collaborative transformative practices that are contingent on both the past and the vision for the future and therefore are profoundly imbued with ideology, ethics, and values. And because acting, being, and knowing are seen from a transformative activist stance as all rooted in, derivative of, and instrumental within a collaborative historical becoming, this stance cuts across and bridges the gaps (a) between individual and social and (b) among ontological, epistemological, and moral-ethical (ideological) dimensions of activity.

Stetsenko, Anna



Source vs. Stance? On the Interpretation and Use of Evidential Utterances by Turkish- vs. English-Speaking Adults  

E-print Network

. Evidentiality, a property, commonly refers to the linguistic marking (in the grammar or the lexicon) of source of knowledge about an asserted event. What is unclear is whether this property also conveys epistemic value (or stance information). This research...

Tosun, Sumeyra



Leaning-Based Travel Interfaces Revisited: Frontal versus Sidewise Stances for Flying in 3D Virtual Spaces  

E-print Network

simulation of skateboarding/snowboarding, the sidewise stance suffers from poor usability due to inefficient life transporters such as the skateboard, the snowboard, and the Segway, several leaning-based travel

Lindeman, Robert W.


Using an electrohydraulic ankle foot orthosis to study modifications in feedforward control during locomotor adaptation to force fields applied in stance  

PubMed Central

Background Adapting to external forces during walking has been proposed as a tool to improve locomotion after central nervous system injury. However, sensorimotor integration during walking varies according to the timing in the gait cycle, suggesting that adaptation may also depend on gait phases. In this study, an ElectroHydraulic AFO (EHO) was used to apply forces specifically during mid-stance and push-off to evaluate if feedforward movement control can be adapted in these 2 gait phases. Methods Eleven healthy subjects walked on a treadmill before (3 min), during (5 min) and after (5 min) exposure to 2 force fields applied by the EHO (mid-stance/push-off; ~10 Nm, towards dorsiflexion). To evaluate modifications in feedforward control, strides with no force field ('catch strides') were unexpectedly inserted during the force field walking period. Results When initially exposed to a mid-stance force field (FF20%), subjects showed a significant increase in ankle dorsiflexion velocity. Catches applied early into the FF20% were similar to baseline (P > 0.99). Subjects gradually adapted by returning ankle velocity to baseline over ~50 strides. Catches applied thereafter showed decreased ankle velocity where the force field was normally applied, indicating the presence of feedforward adaptation. When initially exposed to a push-off force field (FF50%), plantarflexion velocity was reduced in the zone of force field application. No adaptation occurred over the 5 min exposure. Catch strides kinematics remained similar to control at all times, suggesting no feedforward adaptation. As a control, force fields assisting plantarflexion (-3.5 to -9.5 Nm) were applied and increased ankle plantarflexion during push-off, confirming that the lack of kinematic changes during FF50% catch strides were not simply due to a large ankle impedance. Conclusion Together these results show that ankle exoskeletons such as the EHO can be used to study phase-specific adaptive control of the ankle during locomotion. Our data suggest that, for short duration exposure, a feedforward modification in torque output occurs during mid-stance but not during push-off. These findings are important for the design of novel rehabilitation methods, as they suggest that the ability to use resistive force fields for training may depend on targeted gait phases. PMID:19493356

Noel, Martin; Fortin, Karine; Bouyer, Laurent J



Design and functional evaluation of a quasi-passive compliant stance control knee-ankle-foot orthosis.  


In this paper, we present the mechanical design, control algorithm, and functional evaluation of a quasi-passive compliant stance control knee-ankle-foot orthosis. The orthosis implements a spring in parallel with the knee joint during the stance phase of the gait and allows free rotation during the swing phase. The design is inspired by the moment-angle analysis of the knee joint revealing that the knee function approximates that of a linear torsional spring in the stance phase of the gait. Our orthosis aims to restore the natural function of a knee that is impaired by injury, stroke, post-polio, multiple sclerosis, spinal cord injury, patellofemoral pain syndrome, osteoarthritis, and others. Compared with state-of-the-art stance control orthoses, which rigidly lock the knee during the stance phase, the described orthosis intends to provide the natural shock absorption function of the knee in order to reduce compensatory movements both in the affected and unaffected limbs. Preliminary testing on three unimpaired subjects showed that compliant support of the knee provided by the orthosis explained here results in higher gait speed as well as more natural kinematic profiles for the lower extremities when compared with rigid support of the knee provided by an advanced commercial stance control orthosis. PMID:24608684

Shamaei, Kamran; Napolitano, Paul C; Dollar, Aaron M



Developing Inquiry-as-Stance and Repertoires of Practice: Teacher Learning Across Two Settings  

NASA Astrophysics Data System (ADS)

Sixteen science educators joined a science teacher video club for one school year to collaboratively inquire into each other's classroom practice through the use of records of practice including classroom video clips and samples of student work. This group was focused on developing ambitious, equitable science teaching that capitalizes on students' ways of talking and thinking about important science ideas in order to co-construct, test, refine, and revise explanatory models. By analyzing both the teacher-to-teacher interactions taking place in the context of the video club and the on-going classroom teaching practice, this study fills important gaps in our understanding of teacher learning across settings of professional development and classroom practice. This study pursues answers to two groups of guiding questions: (1) How do teachers learn from each other in the context of collaborative inquiry groups, such as a science teacher video club? How do teachers draw upon classroom teaching experiences, re-interpret those experiences, and challenge each other's interpretations and choices made when teaching? (2) How are teachers' professional development experiences connected to and supported by teachers' on-going classroom practice? When the vision of science teaching developed in one context, such as a professional development setting, is different from the vision or teaching developed in another context, such as a local school, how do teachers wrestle with these differences to make choices about instructional practice? Using a sociocultural framework, this study traces the development of inquiry-as-stance as seen in teachers' stance-taking during collegial conversations while also tracing the development of teachers' repertoires of instructional practice. Analysis of discourse during teacher-to-teacher talk as well as during classroom interactions affords insights into the development of an inquiry stance and the evolution of instructional practice at the level of turn-by-turn talk contextualized in real school settings.

Braaten, Melissa L.


Use of physical therapy in a dog with bilateral severe plantigrade stance.  


A 3.5 yr old spayed female Staffordshire terrier weighing 25.5 kg was presented with a 7 wk history of bilateral plantigrade stance in the pelvic limbs directly following an ovariohysterectomy procedure. Upon presentation, the dog had bilateral atrophy of the distal pelvic limb muscles, enlarged popliteal lymph nodes, and ulcerative wounds on the dorsa of her rear paws. Orthopedic examination revealed intact calcaneal tendons bilaterally and neurologic examination localized the lesion to the distal sciatic nerve. A diagnosis of compressive and stretch neuropathy was made affecting the distal sciatic nerve branches. Physical therapy modalities included neuromuscular electrical stimulation, ultrasound, and low-level laser therapy. Other therapeutic modalities included the use of orthotics and progressive wound care. The dog had increased muscle mass, return of segmental reflexes, return of nociception, and the ability to walk on pelvic limbs with higher carriage of the hock 15 mo following presentation. The use of custom orthotics greatly increased the quality of life and other physical therapy modalities may have improved the prognosis in this dog with severe bilateral plantigrade stance due to neuropathy. PMID:25415214

Ree, Jennifer; Hayashi, Kei; Woelz, Jacqueline; Kim, Sun Young



Stance stability with unilateral and bilateral light touch of an external stationary object.  


Unilateral light fingertip touch of a stationary object has a significant stabilizing effect on postural sway during stance. The purpose of this study was to find out if this effect is enhanced by bilateral light touch of parallel stationary objects. The postural sway of 54 healthy subjects was tested in four stance conditions: no touch; unilateral left light touch of the left handle of a walker; unilateral right light touch of the right handle of the same walker; and bilateral light touch of the two handles. During testing, subjects stood blindfolded on two foam pads placed on the left and right force plates of the Tetrax balance system. Testing in each condition lasted 45 s and was executed twice in a random order. As expected, postural sway was significantly reduced by unilateral left or right light fingertip touch. It was significantly further decreased by bilateral light touch. In addition, light touch conditions were associated with a reduction in pressure fluctuations between the heel and forefoot of the same foot as well as those of the contralateral foot, with a concomitant increase in weight shift fluctuations between the two feet. The decrease in postural sway with bilateral light touch suggests cortical modulation of the bilateral touch inputs, with enhancement of the stabilizing response. PMID:16503584

Dickstein, Ruth



Orthotropic HR-pQCT-based FE models improve strength predictions for stance but not for side-way fall loading compared to isotropic QCT-based FE models of human femurs.  


Quantitative computed tomography (QCT) based nonlinear homogenized finite element (hFE) models of the human femur do not take bone?s microstructure into account due to the low resolution of the QCT images. Models based on high-resolution peripheral quantitative computed tomography (HR-pQCT) are able to include trabecular orientation and allow the modeling of a cortical shell. Such a model showed improvements compared to QCT-based models when studying human vertebral bodies. The goal of this study was to compare the femoral strength prediction ability of subject specific nonlinear homogenized FE (hFE) models based on HR-pQCT and QCT images. Thirty-six pairs of femurs were scanned with QCT as well as HR-pQCT, and tested in one-legged stance (STANCE) and side-ways fall (SIDE) configurations up to failure. Non-linear hFE models were generated from HR-pQCT images (smooth meshes) and compared to recently published QCT based models (voxel meshes) as well as experiments with respect to ultimate force. HR-pQCT-based hFE models improved ultimate force (R(2)=0.87 vs 0.80, p=0.02) predictions only in STANCE configuration but not in SIDE (R(2)=0.86 vs 0.84, p=0.6). Damage locations were similar for both types of models. In conclusion, it was shown for the first time on a large femur dataset that a more accurate representation of trabecular orientation and cortex only improve FE predictions in STANCE configuration, where the main trabecular orientation is aligned with the load direction. In the clinically more relevant SIDE configuration, the improvements were not significant. PMID:24508715

Luisier, B; Dall'Ara, E; Pahr, D H



Knowing When to Doubt: Developing a Critical Stance When Learning From Others  

PubMed Central

Children may be biased towards accepting information as true, but the fact remains that children are exposed to misinformation from many sources, and mastering the intricacies of doubt is necessary. The current article examines this issue, focusing on understanding developmental changes and consistencies in children’s ability to take a critical stance towards information. Research is reviewed on children’s ability to detect ignorance, inaccuracy, incompetence, deception, and distortion. Particular emphasis is placed on what this research indicates about how children are reasoning about when to trust and when to doubt. The remainder of the article proposes a framework to evaluate preexisting research and encourage further research, closing with a discussion of several other overarching questions that need to be considered in order to develop a model to explain developmental, individual, and situational differences in children’s ability to evaluate information. PMID:22889395

Mills, Candice M.



Figure 1. Ankle behavior can be approximated by a linear torsional spring in the progression stage of the stance phase of normal gait.  

E-print Network

Figure 1. Ankle behavior can be approximated by a linear torsional spring in the progression stage of the stance phase of normal gait. Abstract--In this paper we explore the mechanical behavior of the ankle in the progression stage of stance during normal walking. We show that the torque/angle behavior of the ankle during

Dollar, Aaron M.


Coordinated, multi-joint, fatigue-resistant feline stance produced with intrafascicular hind limb nerve stimulation  

NASA Astrophysics Data System (ADS)

The production of graceful skeletal movements requires coordinated activation of multiple muscles that produce torques around multiple joints. The work described herein is focused on one such movement, stance, that requires coordinated activation of extensor muscles acting around the hip, knee and ankle joints. The forces evoked in these muscles by external stimulation all have a complex dependence on muscle length and shortening velocities, and some of these muscles are biarticular. In order to recreate sit-to-stand maneuvers in the anesthetized feline, we excited the hind limb musculature using intrafascicular multielectrode stimulation (IFMS) of the muscular branch of the sciatic nerve, the femoral nerve and the main branch of the sciatic nerve. Stimulation was achieved with either acutely or chronically implanted Utah Slanted Electrode Arrays (USEAs) via subsets of electrodes (1) that activated motor units in the extensor muscles of the hip, knee and ankle joints, (2) that were able to evoke large extension forces and (3) that manifested minimal coactivation of the targeted motor units. Three hind limb force-generation strategies were investigated, including sequential activation of independent motor units to increase force, and interleaved or simultaneous IFMS of three sets of six or more USEA electrodes that excited the hip, knee and ankle extensors. All force-generation strategies evoked stance, but the interleaved IFMS strategy also reduced muscle fatigue produced by repeated sit-to-stand maneuvers compared with fatigue produced by simultaneous activation of different motor neuron pools. These results demonstrate the use of interleaved IFMS as a means to recreate coordinated, fatigue-resistant multi-joint muscle forces in the unilateral hind limb. This muscle activation paradigm could provide a promising neuroprosthetic approach for the restoration of sit-to-stand transitions in individuals who are paralyzed by spinal cord injury, stroke or disease.

Normann, R. A.; Dowden, B. R.; Frankel, M. A.; Wilder, A. M.; Hiatt, S. D.; Ledbetter, N. M.; Warren, D. A.; Clark, G. A.



A simple new device to examine human stance: the totter-slab.  


This article describes a new measuring device to investigate balancing strategies of human stance: the totter-slab, i.e., a standing plate suspended with steel cables to hooks on a steel frame. First, we analysed the physical properties of the device by recording free oscillations under different conditions [varying amplitude, mass and centre of mass (COM) height]. This allowed us to determine the eigenfrequency f and the damping coefficient D<1 Ns/m for each trial. The trials showed that the measured damped eigenfrequency of f is approximately 0.63 Hz is barely dependent on the mass loaded. The ratio D/M is approximately 0.015 1/s is a constant almost independent of the different conditions. Furthermore, we determined the stiffnesses of the suspending cables and their suspension points to check for potential energy storage capacity of the totter-slab. We found that the totter-slab is a useful, well-defined, reliable and developable measuring device for different non-rigid-ground stance conditions. In a second part of the investigation, we compared the frequency spectra of six subjects balancing on the totter-slab with their spectra while standing quietly on a force plate fixed to the ground. The totter-slab spectra showed two distinct, dominant peak regions at approximately 0.3 and 1.1 Hz. This finding enforces the double inverted pendulum to be an adequate model particularly for balancing on the totter-slab. Compared with the firm ground condition, these two peak regions were more pronounced when balancing on the totter-slab. However, there is a variety of frequencies in the region 0.2...1.5 Hz specific for an individual subject in both balancing conditions. PMID:20128743

Roth, Robin; Wank, Veit; Müller, Otto; Hochwald, Harald; Günther, Michael



The Transformative Power of Taking an Inquiry Stance on Practice: Practitioner Research as Narrative and Counter-Narrative  

ERIC Educational Resources Information Center

Within the ever-developing, intersecting, and overlapping contexts of globalization, top-down policy, mandates, and standardization of public and higher education, many conceptualize and position practitioner research as a powerful stance and a tool of social, communal, and educational transformation, a set of methodological processes that…

Ravitch, Sharon M.



Cognitive Space 1 The Strong Cognitive Stance as a Conceptual Basis for the Role of Information in  

E-print Network

in information system development. 1. Introduction: The Human Aspects of Cognitive Space Many groupsCognitive Space 1 The Strong Cognitive Stance as a Conceptual Basis for the Role of Abstract This paper analyzes different approaches that have been taken to describe and utilize cognitive

Newby, Gregory B.


Connecting Learning and Identity Development through a Transformative Activist Stance: Application in Adolescent Development in a Child Welfare Program  

Microsoft Academic Search

This paper addresses the relationship between identity and learning and how their integration in adolescence is an important part of short- and long-term developmental dynamics. We discuss how social practice theories can be expanded from a position termed ‘transformative activist stance’ that puts emphasis on collaborative practice aimed at changing the world and enacted by individual activist contributions as the

Eduardo Vianna; Anna Stetsenko



Sample entropy characteristics of movement for four foot types based on plantar centre of pressure during stance phase  

PubMed Central

Background Motion characteristics of CoP (Centre of Pressure, the point of application of the resultant ground reaction force acting on the plate) are useful for foot type characteristics detection. To date, only few studies have investigated the nonlinear characteristics of CoP velocity and acceleration during the stance phase. The aim of this study is to investigate whether CoP regularity is different among four foot types (normal foot, pes valgus, hallux valgus and pes cavus); this might be useful for classification and diagnosis of foot injuries and diseases. To meet this goal, sample entropy, a measure of time-series regularity, was used to quantify the CoP regularity of four foot types. Methods One hundred and sixty five subjects that had the same foot type bilaterally (48 subjects with healthy feet, 22 with pes valgus, 47 with hallux valgus, and 48 with pes cavus) were recruited for this study. A Footscan® system was used to collect CoP data when each subject walked at normal and steady speed. The velocity and acceleration in medial-lateral (ML) and anterior-posterior (AP) directions, and resultant velocity and acceleration were derived from CoP. The sample entropy is the negative natural logarithm of the conditional probability that a subseries of length m that matches pointwise within a tolerance r also matches at the next point. This was used to quantify variables of CoP velocity and acceleration of four foot types. The parameters r (the tolerance) and m (the matching length) for sample entropy calculation have been determined by an optimal method. Results It has been found that in order to analyze all CoP parameters of velocity and acceleration during the stance phase of walking gait, for each variable there is a different optimal r value. On the contrary, the value m=4 is optimal for all variables. Sample entropies of both velocity and acceleration in AP direction were highly correlated with their corresponding resultant variables for r>0.91. The sample entropy of the velocity in AP direction was moderately correlated with the one of the acceleration in the same direction (r?0.673), as well as with the resultant acceleration (r?0.660). The sample entropy of resultant velocity was moderately correlated with the one of the acceleration in AP direction, as well as with the resultant acceleration (for the both r?0.689). Moderate correlations were found between variables for the left foot and their corresponding variables for the right foot. Sample entropies of AP velocity, resultant velocity, AP acceleration, and resultant acceleration of the right foot as well as AP velocity and resultant velocity of the left foot were, respectively, significantly different among the four foot types. Conclusions It can be concluded that the sample entropy of AP velocity (or the resultant velocity) of the left foot, ML velocity, resultant velocity, ML acceleration and resultant acceleration could serve for evaluation of foot types or selection of appropriate footwear. PMID:24112763



Preferred placement of the feet during quiet stance: development of a standardized foot placement for balance testing  

Microsoft Academic Search

Objective. To establish a standardized stance position for balance testing based on average preferred foot placement, and to compare this to existing standards.Design. Cross-sectional study.Background. It has been shown that the orientation of the feet can have a marked influence on the results obtained during balance testing, prompting the need for standardized foot positioning. Unfortunately, current recommendations do not appear

WE McIlroy; BE Maki



The effect of prosthetic feedback on the strategies and synergies used by vestibular loss subjects to control stance  

PubMed Central

Background This study investigated changes in stance movement strategies and muscle synergies when bilateral peripheral vestibular loss (BVL) subjects are provided feedback of pelvis sway angle. Methods Six BVL (all male) and 7 age-matched male healthy control (HC) subjects performed 3 stance tasks: standing feet hip width apart, eyes closed, on a firm and foam surface, and eyes open on foam. Pelvis and upper trunk movements were recorded in the roll and pitch planes. Surface EMG was recorded from pairs of antagonistic muscles at the lower leg, trunk and upper arm. Subjects were first assessed without feedback. Then, they received training with vibrotactile, auditory, and fall-warning visual feedback during stance tasks before being reassessed with feedback. Results Feedback reduced pelvis sway angle displacements to values of HCs for all tasks. Movement strategies were reduced in amplitude but not otherwise changed by feedback. These strategies were not different from those of HCs before or after use of feedback. Low frequency motion was in-phase and high frequency motion anti-phasic. Feedback reduced amplitudes of EMG, activity ratios (synergies) of antagonistic muscle pairs and slightly reduced baseline muscle activity. Conclusions This is the first study demonstrating how vestibular loss subjects achieve a reduction of sway during stance with prosthetic feedback. Unchanged movement strategies with reduced amplitudes are achieved with improved antagonistic muscle synergies. This study suggests that both body movement and muscle measures could be explored when choosing feedback variables, feedback location, and patient groups for prosthetic devices which reduce sway of those with a tendency to fall. PMID:24354579



Initiation of movement from quiet stance: comparison of gait and stepping in elderly subjects of different levels of functional ability  

Microsoft Academic Search

This study describes how elderly subjects initiate gait, and step from a position of quiet stance. Based on scores from selected standardized tests subjects were placed in either a high (HFL) or low functional level (LFL) group and were asked to initiate gait, step onto a 10cm high, 1.22m wide curb and step over a 10cm high, 9cm wide obstacle

Denis Brunt; Valeria Santos; Hyeong Dong Kim; Kathye Light; Charles Levy



To what extent can linear finite element models of human femora predict failure under stance and fall loading configurations?  


Proximal femur strength estimates from computed tomography (CT)-based finite element (FE) models are finding clinical application. Published models reached a high in-vitro accuracy, yet many of them rely on nonlinear methodologies or internal best-fitting of parameters. The aim of the present study is to verify to what extent a linear FE modelling procedure, fully based on independently determined parameters, can predict the failure characteristics of the proximal femur in stance and sideways fall loading configurations. Fourteen fresh-frozen cadaver femora were CT-scanned. Seven femora were tested to failure in stance loading conditions, and seven in fall. Fracture was monitored with high-speed videos. Linear FE models were built from CT images according to a procedure already validated in the prediction of strains. An asymmetric maximum principal strain criterion (0.73% tensile, 1.04% compressive limit) was used to define a node-based risk factor (RF). FE-predicted failure load, mode (tensile/compressive) and location were determined from the first node reaching RF=1. FE-predicted and measured failure loads were highly correlated (R(2)=0.89, SEE=814N). In all specimens, FE models correctly identified the failure mode (tensile in stance, compressive in fall) and the femoral region where fracture started (supero-lateral neck aspect). The location of failure onset was accurately predicted in eight specimens. In summary, a simple FE model, adaptable in the future to multiple loads (e.g. including muscles), was highly correlated with experimental failure in two loading conditions on specimens ranging from normal to osteoporotic. Thus, it can be suitable for use in clinical studies. PMID:25261321

Schileo, Enrico; Balistreri, Luca; Grassi, Lorenzo; Cristofolini, Luca; Taddei, Fulvia



Using Argument-Driven Inquiry to enhance students' argument sophistication when supporting a stance in the context of Socioscientific Issues  

NASA Astrophysics Data System (ADS)

This quasi-experimental study assesses the extent to which the Argument-Driven Inquiry (ADI) instructional model enhances undergraduate students' abilities to generate quality arguments supporting their stance in the context of a Socioscientific Issue (SSI) as compared to students experiencing a traditional style of instruction. Enhancing the quality of undergraduate students' arguments in the context of SSI can serve as an indirect measure of their scientific literacy and their ability to make sound decisions on issues that are inherently scientific but also involve social implications. Data collected in this study suggest that the undergraduate students experiencing the ADI instruction more readily provide rationales in their arguments supporting their decisions regarding two SSI-tasks as compared to a group of undergraduate students experiencing traditional instruction. This improvement in argument quality and gain in scientific literacy was achieved despite the overall lower SSI related content knowledge of the ADI students. Furthermore, the gap between the argument quality of those students with high versus low SSI related content knowledge was closed within the ADI group, while the same gap persisted post-intervention within the traditional instruction students. The role of students' epistemological sophistication was also investigated, which showed that neither instructional strategy was effective at shifting students' epistemological sophistication toward an evaluativist stance. However, the multiplists within the ADI group were able to significantly increase the sophistication of their arguments whereas the traditional students were not. There were no differences between the quality of arguments generated by the evaluativist students with either the treatment or comparison groups. Finally, the nature of the justifications used by the students revealed that the students (both comparison and treatment groups) did not invoke science-based justifications when supporting their stance, despite students' self-reports that scientific content knowledge accounted for the greatest influence on their stance, related to the SSI tasks. The results of this study suggest that the scientific habits of mind the students learned in the context of ADI investigations are transferred to the novel SSI contexts. Implications for the use of argument-based instructional models to enhance the generation of socioscientific arguments and to promote the development of scientific literacy are also discussed.

Grooms, Jonathon A.


Intra-articular Contact Stress Distributions at the Ankle throughout Stance Phase – Patient-Specific Finite Element Analysis as a Metric of Degeneration Propensity  

PubMed Central

A contact finite element (FE) formulation is introduced, amenable to patient-specific analysis of cumulative cartilage mechano-stimulus attributable to habitual functional activity. CT scans of individual human ankles are segmented to delineate bony margins. Each bone surface is projected outward to create a second surface, and the intervening volume is then meshed with continuum hexahedral elements. The tibia is positioned relative to the talus into a weight-bearing apposition. The articular members are first engaged under light preload, then plantar-/dorsi-flexion kinematics and resultant loadings are input for serial FE solutions at 13 instants of the stance phase of level walking gait. Cartilage stress histories are post-processed to recover distributions of cumulative stress-time mechano-stimulus, a metric of degeneration propensity. Consistency in computed contact stress exposures presented for seven intact ankles stood in contrast to the higher magnitude and more focal exposures in an incongruously reduced tibial plafond fracture. This analytical procedure provides patient-specific estimates of degeneration propensity due to various mechanical abnormalities, and it provides a platform from which the mechanical efficacy of alternative surgical interventions can be estimated. PMID:16520960

Anderson, Donald D.; Goldsworthy, Jane K.; Shivanna, Kiran; Grosland, Nicole M.; Pedersen, Douglas R.; Thomas, Thaddeus P.; Tochigi, Yuki; Marsh, J.Lawrence; Brown, Thomas D.



Force-sensitive afferents recruited during stance encode sensory depression in the contralateral swinging limb during locomotion  

PubMed Central

Afferent feedback alters muscle activity during locomotion and must be tightly controlled. As primary afferent depolarization-induced presynaptic inhibition (PAD-PSI) regulates afferent signaling, we investigated hind limb PAD-PSI during locomotion in an in vitro rat spinal cord-hind limb preparation. We compared the relation of PAD-PSI, measured as dorsal root potentials (DRPs), to observed ipsilateral and contralateral limb endpoint forces. Afferents activated during stance-phase force strongly and proportionately influenced DRP magnitude in the swinging limb. Responses increased with locomotor frequency. Electrical stimulation of contralateral afferents also preferentially evoked DRPs in the opposite limb during swing (flexion). Nerve lesioning in conjunction with kinematic results support a prominent contribution from toe Golgi tendon organ afferents. Thus, force-dependent afferent feedback during stance binds interlimb sensorimotor state to a proportional PAD-PSI in the swinging limb, presumably to optimize interlimb coordination. These results complement known actions of ipsilateral afferents on PAD-PSI during locomotion. PMID:23531008

Hochman, Shawn; Hayes, Heather Brant; Speigel, Iris; Chang, Young-Hui



Comparison of the effect of selected muscle groups fatigue on postural control during bipedal stance in healthy young women  

PubMed Central

Background: The maintenance of balance is an essential requirement for the performance of daily tasks and sporting activities and muscular fatigue is a factor to impair postural control, so this study was done to compare the effect of selected muscle groups fatigue on postural control during bipedal stance in healthy subjects. Materials and Methods: Fifteen healthy female students (24.3 ± 2.6 years) completed three testing session with a break period of at least 2 days. During each session, postural control was assessed during two 30-s trials of bipedal stance with eyes close before and after the fatigue protocol. Fatigue protocols were performed by 60% of their unfatigued Maximum Voluntary Contraction of unilateral ankle plantar flexors, bilateral lumbar extensors and bilateral neck extensors. One of the three fatigue protocols was performed on each session. Results: The result showed that fatigue had a significant effect on COP velocity and it increase COP velocity but there was not found any difference in postural sway between muscle groups. Conclusion: Localized muscle fatigue caused deficits in postural control regardless of the location of fatigue. Authors suggest the possibility of the contributions of central mechanisms to postural deficits due to fatigue and it seems that difference was not between muscle groups due to central fatigue. PMID:24403706

Shirazi, Zahra Rojhani; Jahromi, Fatemeh Nikhalat



A robust 3D finite element simulation of human proximal femur progressive fracture under stance load with experimental validation.  


Clinical implementation of quantitative computed tomography-based finite element analysis (QCT/FEA) of proximal femur (hip) fractures requires (i) to develop a bone material behavior able to describe the progressive fracturing process until complete failure of the hip. And (ii) to validate the model with realistic test data that represent typical hip fractures. The objective of the current study was to develop and experimentally validate an accurate 3D finite element (FE) model coupled to a quasi-brittle damage law to simulate human proximal femur fracture considering the initiation and progressive propagation of multiple cracks phases under quasi-static load. The model is based on continuum damage mechanics that can predict hip fracture in more adequate physical terms than criteria-based fracture models. In order to validate the model, ten human proximal femurs were tested until complete fracture under one-legged stance quasi-static load. QCT/FE models were generated and FE simulations were performed on these femurs with the same applied loads and boundary conditions than in the stance experiments. The proposed FE model leads to excellent agreement (R(2) = 0.9432) between predicted and measured results concerning the shape of the force-displacement curve (yielding and fracturing) and the profile of the fractured edge. The motivation of this work was to propose a FE model for possible clinical use with a good compromise between complexity and capability of the simulation. PMID:23864338

Hambli, Ridha; Allaoui, Samir



Repeatability of stance phase kinematics from a multi-segment foot model in people aged 50 years and older.  


Confidence in 3D multi-segment foot models has been limited by a lack of repeatability data, particularly in older populations that may display unique functional foot characteristics. This study aimed to determine the intra and inter-observer repeatability of stance phase kinematic data from a multi-segment foot model described by Leardini et al. [2] in people aged 50 years or older. Twenty healthy adults participated (mean age 65.4 years SD 8.4). A repeated measures study design was used with data collected from four testing sessions on two days from two observers. Intra (within-day and between-day) and inter-observer coefficient of multiple correlations revealed moderate to excellent similarity of stance phase joint range of motion (0.621-0.975). Relative to the joint range of motion (ROM), mean differences (MD) between sessions were highest for the within-day comparison for all planar ROM at the metatarsus-midfoot articulation (sagittal plane ROM 5.2° vs. 3.9°, MD 3.1°; coronal plane ROM 3.9 vs. 3.1°, MD 2.3°; transverse plane ROM 6.8° vs. 5.16°, MD 3.5°). Consequently, data from the metatarsus-midfoot articulation in the Istituto Ortopedico Rizzoli (IOR) foot model in adults aged over 50 years needs to be considered with respect to the findings of this study. PMID:23219780

Arnold, John B; Mackintosh, Shylie; Jones, Sara; Thewlis, Dominic



Restoration of Stance Phase Knee Flexion during Walking after Spinal Cord Injury using a Variable Impedance Orthosis  

PubMed Central

A hybrid neuroprosthesis (HNP) combines lower extremity bracing with functional neuromuscular stimulation (FNS) to restore walking function and enhance the efficiency of ambulation. This report details the development of a novel HNP containing a variable impedance knee mechanism (VIKM) capable of supporting the knee against collapse while allowing controlled stance phase knee flexion. The design of a closed loop, finite state controller for coordination of VIKM activity with FNS-driven gait is presented. The controller is verified in testing during able bodied gait. The improved functionality provided by this system has the potential to delay the onset of fatigue and to expand FNS driven gait to allow walking over uneven terrains and down stairs. PMID:22254383

Bulea, Thomas C.; Kobetic, Rudi; Triolo, Ronald. J.



Changes in length of the plantar aponeurosis during the stance phase of gait--an in vivo dynamic fluoroscopic study.  


In locomotion, ligaments and muscles have been recognized to support the arch of the foot. However, it remains unclear to what extent the passive and active structures of the lower extremity support the longitudinal arch of the foot during walking. In this study, the mechanical function of the plantar aponeurosis (PA) is investigated by elongation measurements in vivo during the stance phase of gait, in combination with measurements of the mechanical properties of the PA in vitro. Fluoroscopy was used to measure the dynamic changes in PA length and the angular motion of the metatarsophalangeal joint of the first ray, measured during the stance phase (StPh) in 11 feet. Simultaneously, ground forces were measured. Additionally, four cadaver feet delivered topographic information relating to the PA, and three autopsy specimens of PA served to determine the in vitro mechanical properties of PA. The present study revealed a non-significant peak average PA shortening of 0.48% at about 32.5% StPh, followed by a significant average peak elongation of 3.6% at 77.5% StPh. This average peak elongation of 3.6% corresponds to a force of 292N, as estimated by mechanical testing of the autopsy PA specimens. Considering the maximum peak elongation measured in one volunteer of 4.8% at 76% StPh, a peak PA load of 488N might be expected. Hence, with an average body weight of 751N, as allocated to the 11 investigated feet, this maximum peak force would correspond to about 0.65×body weight. As far as we are aware, this is the first report on a dynamic fluoroscopic study of the PA in gait with an appreciable number of feet (11 feet). In conclusion, muscles contribute to support of the longitudinal arch of the foot and can possibly relax the PA during gait. The 'windlass effect' for support of the arch in this context is therefore questionable. PMID:25113063

Fessel, G; Jacob, H A C; Wyss, Ch; Mittlmeier, Th; Müller-Gerbl, M; Büttner, A



Origins of Children's Externalizing Behavior Problems in Low-Income Families: Toddlers’ Willing Stance toward their Mothers as the Missing Link  

PubMed Central

Although children's active role in socialization has been long acknowledged, relevant research has typically focused on children's difficult temperament or negative behaviors that elicit coercive and adversarial processes, largely overlooking their capacity to act as positive, willing, even enthusiastic, active socialization agents. We studied the willing, receptive stance toward their mothers in 186 24-44-month-old children in a low-income sample. Confirmatory Factor Analysis supported a latent construct of willing stance, manifested as children's responsiveness to mothers in naturalistic interactions, responsive imitation in teaching contexts, and committed compliance with maternal prohibitions, all observed in the laboratory. Structural Equation Modeling analyses confirmed that ecological adversity undermined maternal responsiveness and responsiveness, in turn, was linked to children's willing stance. A compromised willing stance predicted externalizing behavior problems, assessed 10 months later, and fully mediated the links between maternal responsiveness and those outcomes. Ecological adversity had a direct, unmediated effect on internalizing behavior problems. Considering children's active role as willing, receptive agents capable of embracing parental influence can lead to a more complete understanding of detrimental mechanisms that link ecological adversity with antisocial developmental pathways. It can also inform research on the normative socialization process, consistent with the objectives of developmental psychopathology. PMID:24229537

Kochanska, Grazyna; Kim, Sanghag; Boldt, Lea J.



Taking an Effective Authorial Stance in Academic Writing: Making the Linguistic Resources Explicit for L2 Writers in the Social Sciences  

ERIC Educational Resources Information Center

Taking an assertive stance toward research being reviewed or reported is a challenging task for second language writers. This aspect of interpersonal meaning is especially difficult to address through direct instruction, as attention to particular grammatical and lexical choices outside of contexts of use is not enough to help students develop the…

Chang, Peichin; Schleppegrell, Mary



Weather outlook for spring and summer 2010: Effects on planting clam seed The new FDA takes a strong stance against raw molluscan shellfish  

E-print Network

a strong stance against raw molluscan shellfish It has now been six months since the U.S. Food and Drug the Alligator Harbor and Gulf Jackson lease areas, while the Indian River lease area averaged 52o F. Colder to neutral conditions until summer. Fortunately, rivers have crested. Spring flood conditions should

Florida, University of


The Role of Knee Positioning and Range-of-Motion on the Closed-Stance Forehand Tennis Swing  

PubMed Central

This paper discusses the role of knee positioning and range-of- motion on the closed-stance forehand tennis swing. The analyses of tennis swing mechanics were performed using a computer model comprised of a full-body model of a human and an inertial model of a racket. The model was driven by subject forehand swings (16 female college-level subjects) recorded with a high-speed digital motion analysis system. The study discovered that both initial knee positioning and range-of-motion were positively related to racket velocity and characteristic of more skilled players. The direct effects of knee positioning and range-of-motion on racket movement are minimal, however there are several indirect biomechanical effects on the forehand motion such as movement of the body mass center, work of the knee, hip and back joints, and the angular range-of-motion of the hips and torso. Some of these indirect effects were related to racket velocity and characteristic of more skilled players. Factors that influenced knee positioning and range-of-motion include years of playing, amount of coaching, and body style. Efforts to both increase and restrict the knee movements of the subjects resulted in substantially lower racket velocities (and other detrimental biomechanical effects) implying that there may be optimal knee positions and range-of-motion for a given subject. The most skilled subject exhibited a high degree of consistency of knee positioning and range-of-motion. This subject adjusted for varying ball height through modified initial knee positioning while maintaining fairly constant ranges-of-motion. Key pointsInitial knee positioning and range-of-motion were positively related to racket velocity and characteristic of more skilled players for the closed stance forehand motion.Knee positioning and range-of-motion had several indirect biomechanical effects on the forehand motion such as movement of the body mass center, work of the knee, hip and back joints, and the angular range-of-motion of the hips and torso.Efforts to both increase and restrict the knee movements resulted in substantially lower racket velocities implying that there may be optimal knee positions and range-of-motion for a given subject.The most skilled subject exhibited a high degree of consistency of knee positioning and range-of-motion. This subject adjusted for varying ball height through modified initial knee positioning while maintaining fairly constant ranges-of-motion. PMID:24150143

Nesbit, Steven M.; Serrano, Monika; Elzinga, Mike



The influence of visual information on multi-muscle control during quiet stance: a spectral analysis approach.  


Standing upright requires the coordination of neural drives to a large set of muscles involved in controlling human bipedal stance (i.e., postural muscles). The coordination may deteriorate in situations where standing is performed under more challenging circumstances, such as standing on a smaller base of support or not having adequate visual information. The present study investigates the role of common neural inputs in the organization of multi-muscle synergies and the effects of visual input disruption to this mechanism of control. We analyzed the strength and distribution of correlated neural inputs (measured by intermuscular coherence) to six postural muscles previously recognized as components of synergistic groups involved in the maintenance of the body's vertical positioning. Two experimental conditions were studied: quiet bipedal stance performed with opened eyes (OEs) and closed eyes (CEs). Nine participants stood quietly for 30 s while the activity of the soleus, biceps femoris, lumbar erector spinae, tibialis anterior, rectus femoris, and rectus abdominis muscles were recorded using surface electrodes. Intermuscular (EMG-EMG) coherence was estimated for 12 muscle pairs formed by these muscles, including pairs formed solely by either posterior, anterior, or mixed (one posterior and one anterior) muscles. Intermuscular coherence was only found to be significant for muscle pairs formed solely by either posterior or anterior muscles, and no significant coherence was found for mixed muscle pairs. Significant intermuscular coherence was only found within a distinct frequency interval bounded between 1 and 10 Hz when visual input was available (OEs trials). The strength of correlated neural inputs was similar across muscle pairs located in different joints but executing a similar function (pushing body either backward or forward) suggesting that synergistic postural groups are likely formed based on their functional role instead of their anatomical location. Absence of visual information caused a significant decrease in intermuscular coherence. These findings are consistent with the hypothesis that correlated neural inputs are a mechanism used by the CNS to assemble synergistic muscle groups. Further, this mechanism is affected by interruption of visual input. PMID:25407521

Danna-Dos-Santos, Alessander; Degani, Adriana M; Boonstra, Tjeerd W; Mochizuki, Luis; Harney, Allison M; Schmeckpeper, Megan M; Tabor, Lori C; Leonard, Charles T



An analysis of directional changes in the center of pressure trajectory during stance  

Microsoft Academic Search

This study proposes a new approach of posturography analysis, which enables the evaluation of directional changes in the center of pressure trajectory. The concept is similar to that of so-called “stabilogram diffusion analysis”. Instead of calculating the distance traveled by the center of pressure in a certain time interval, this new method calculates the cosine of the instantaneous velocity vectors

Akinori Nagano; Hisahito Noritake; Zhi-Wei Luo



Cross-correlation between EMG and center of gravity during quiet stance: theory and simulations  

Microsoft Academic Search

Several signal processing tools have been employed in the experimental study of the postural control system in humans. Among\\u000a them, the cross-correlation function has been used to analyze the time relationship between signals such as the electromyogram\\u000a and the horizontal projection of the center of gravity. The common finding is that the electromyogram precedes the biomechanical\\u000a signal, a result that

André Fabio Kohn



First trial and StartReact effects induced by balance perturbations to upright stance.  


Postural responses (PR) to a balance perturbation differ between the first and subsequent perturbations. One explanation for this first trial effect is that perturbations act as startling stimuli that initiate a generalized startle response (GSR) as well as the PR. Startling stimuli, such as startling acoustic stimuli (SAS), are known to elicit GSRs, as well as a StartReact effect, in which prepared movements are initiated earlier by a startling stimulus. In this study, a StartReact effect paradigm was used to determine if balance perturbations can also act as startle stimuli. Subjects completed two blocks of simple reaction time trials involving wrist extension to a visual imperative stimulus (IS). Each block included 15 CONTROL trials that involved a warning cue and subsequent IS, followed by 10 repeated TEST trials, where either a SAS (TESTSAS) or a toes-up support-surface rotation (TESTPERT) was presented coincident with the IS. StartReact effects were observed during the first trial in both TESTSAS and TESTPERT conditions as evidenced by significantly earlier wrist movement and muscle onsets compared with CONTROL. Likewise, StartReact effects were observed in all repeated TESTSAS and TESTPERT trials. In contrast, GSRs in sternocleidomastoid and PRs were large in the first trial, but significantly attenuated over repeated presentation of the TESTPERT trials. Results suggest that balance perturbations can act as startling stimuli. Thus first trial effects are likely PRs which are superimposed with a GSR that is initially large, but habituates over time with repeated exposure to the startling influence of the balance perturbation. PMID:23945786

Campbell, A D; Squair, J W; Chua, R; Inglis, J T; Carpenter, M G



Virtual patients as activities: exploring the research implications of an activity theoretical stance.  


Virtual patients are computer-based simulators of patient encounters for the purposes of instruction, practice, and assessment. Although virtual patients have been around for some time they have yet to become part of mainstream medical education. A major reason for this would seem to be a lack of clarity as to what educational value virtual patients actually have. This paper argues that virtual patients should be seen as activities rather than artifacts and that activity theory can be used to generate different ways to frame scholarship in and around virtual patients. Drawing on the work of Leont'ev and Engeström this paper describes a range of perspectives based on the operations, actions, and objectives in and around virtual patients; the use of virtual patients to mediate activities; and the sociocultural context and the participants in virtual patient activities. This approach allows us to move beyond the 'does or does not work' discourse of much of the existing scholarship around virtual patients and, to an extent, around educational technologies as a whole. Activity perspectives, and activity theory in particular, offer new horizons for research and evaluation that address many of the limitations of intervention-based paradigms of inquiry. PMID:25082311

Ellaway, Rachel H



Effect of using poles on foot-ground kinetics during stance phase in trail running.  


The aim of this study was to investigate the effect of using poles on foot-ground interaction during trail running with slopes of varying incline. Ten runners ran on a loop track representative of a trail running field situation with uphill (+9°), level and downhill (-6°) sections at fixed speed (3.2 m.s(-1)). Experimental conditions included running with (WP) and without (NP) the use of poles for each of the three slopes. Several quantitative and temporal foot-ground interaction parameters were calculated from plantar pressure data measured with a portable device. Using poles induced a decrease in plantar pressure intensity even when the running velocity stayed constant. However, the localisation and the magnitude of this decrease depended on the slope situations. During WP level running, regional analysis of the foot highlighted a decrease of the force time integral (FTI) for absolute (FTIabs; -12.6%; P<0.05) and relative values (FTIrel; -14.3%; P<0.05) in the medial forefoot region. FTIabs (-14.2%; P<0.05) and duration of force application (?t; -13.5%; P<0.05) also decreased in the medial heel region when WP downhill running. These results support a facilitating effect of pole use for propulsion during level running and for the absorption phase during downhill running. PMID:24050463

Daviaux, Yannick; Hintzy, Frédérique; Samozino, Pierre; Horvais, Nicolas



Influence of Electrotactile Tongue Feedback on Controlling Upright Stance during Rotational and/or Translational Sway-referencing with Galvanic Vestibular Stimulation  

NASA Technical Reports Server (NTRS)

Integration of multi-sensory inputs to detect tilts relative to gravity is critical for sensorimotor control of upright orientation. Displaying body orientation using electrotactile feedback to the tongue has been developed by Bach-y-Rita and colleagues as a sensory aid to maintain upright stance with impaired vestibular feedback. MacDougall et al. (2006) recently demonstrated that unpredictably varying Galvanic vestibular stimulation (GVS) significantly increased anterior-posterior (AP) sway during rotational sway referencing with eyes closed. The purpose of this study was to assess the influence of electrotactile feedback on postural control performance with pseudorandom binaural bipolar GVS. Postural equilibrium was measured with a computerized hydraulic platform in 10 healthy adults (6M, 4F, 24-65 y). Tactile feedback (TF) of pitch and roll body orientation was derived from a two-axis linear accelerometer mounted on a torso belt and displayed on a 144-point electrotactile array held against the anterior dorsal tongue (BrainPort, Wicab, Inc., Middleton, WI). Subjects were trained to use TF by voluntarily swaying to draw figures on their tongue, both with and without GVS. Subjects were required to keep the intraoral display in their mouths on all trials, including those that did not provide TF. Subjects performed 24 randomized trials (20 s duration with eyes closed) including four support surface conditions (fixed, rotational sway-referenced, translating the support surface proportional to AP sway, and combined rotational-translational sway-referencing), each repeated twice with and without GVS, and with combined GVS and TF. Postural performance was assessed using deviations from upright (peak-to-peak and RMS sway) and convergence toward stability limits (time and distance to base of support boundaries). Postural stability was impaired with GVS in all platform conditions, with larger decrements in performance during trials with rotation sway-referencing. Electrotactile feedback improved performance with GVS toward non-GVS levels, again with the greatest improvement during trials with rotation sway-referencing. These results demonstrate the effectiveness of tongue electrotactile feedback in providing sensory substitution to maintain postural stability with distorted vestibular input.

Wood, Scott J.; Tyler, Mitchell E.; Bach-y-Rita, Paul; MacDougall, Hamish G.; Moore, Steven T.; Stallings, Valerie L.; Paloski, William H.; Black, F. Owen



US Definitions, Current Use, and FDA Stance on Use of Platelet-Rich Plasma in Sports Medicine.  


With increased utilization of platelet-rich plasma (PRP), it is important for clinicians to understand the United States, the Food and Drug Administration (FDA) regulatory role and stance on PRP. Blood products such as PRP fall under the prevue of FDA's Center for Biologics Evaluation and Research (CBER). CBER is responsible for regulating human cells, tissues, and cellular and tissue-based products. The regulatory process for these products is described in the FDA's 21 CFR 1271 of the Code of Regulations. Under these regulations, certain products including blood products such as PRP are exempt and therefore do not follow the FDA's traditional regulatory pathway that includes animal studies and clinical trials. The 510(k) application is the pathway used to bring PRP preparation systems to the market. The 510(k) application allows devices that are "substantially equivalent" to a currently marketed device to come to the market. There are numerous PRP preparation systems on the market today with FDA clearance; however, nearly all of these systems have 510(k) clearance for producing platelet-rich preparations intended to be used to mix with bone graft materials to enhance bone graft handling properties in orthopedic practices. The use of PRP outside this setting, for example, an office injection, would be considered "off label." Clinicians are free to use a product off-label as long as certain responsibilities are met. Per CBER, when the intent is the practice of medicine, clinicians "have the responsibility to be well informed about the product, to base its use on firm scientific rationale and on sound medical evidence, and to maintain records of the product's use and effects." Finally, despite PRP being exempted, the language in 21 CFR 1271 has caused some recent concern over activated PRP; however to date, the FDA has not attempted to regulate activated PRP. Clinicians using activated PRP should be mindful of these concerns and continued to stay informed. PMID:25268794

Beitzel, Knut; Allen, Donald; Apostolakos, John; Russell, Ryan P; McCarthy, Mary Beth; Gallo, Gregory J; Cote, Mark P; Mazzocca, Augustus D




PubMed Central

In an ovine femur model, proliferative woven bone fills critical sized defects enveloped by periosteum within two weeks of treatment with the one stage bone transport surgery. We hypothesize that mechanical loading modulates this process. Using high-definition optical strain measurements we determined prevailing periosteal strains for normal and surgically treated ovine femora subjected ex vivo to compressive loads simulating in vivo stance shifting (n=3 per group, normal versus treated). We determined spatial distribution of calcein green, a label for bone apposition in first the two weeks after surgery, in 15°, 30°, and 45° sectors of histological cross sections through the middle of the defect zone (n=6 bones, 3–4 sections/bone). Finally, we correlated early bone formation to either the maximal periosteal strain or the net change in maximal periosteal strain. We found that treatment with the one stage bone transport surgery profoundly changes the mechanical environment of cells within the periosteum during stance shift loading. The pattern of early bone formation is repeatable within and between animals and relates significantly to the actual strain magnitude prevailing in the periosteum during stance shift loading. Interestingly, early bone apposition after the surgery correlates more to the maximal net change in strain (above circa 2000–3000 µ?, in tension or compression) rather than strain magnitude per se, providing further evidence that changes in cell shape may drive mechanoadaptation by progenitor cells. These important insights regarding mechanobiologic factors that enhance rapid bone generation in critical sized defects can be translated to the tissue and organ scale, providing a basis for the development of best practices for clinical implementation and the definition of movement protocols to enhance the regenerative effect. PMID:21271290

McBride, Sarah H; Dolejs, Scott; Brianza, Stefano; Knothe, Ulf; Knothe Tate, Melissa L




ERIC Educational Resources Information Center

When a teacher gives their time to a student, it is more significant to that student than anything else one could do for him or her. Music teachers deal with time all the time. Someone once said that "time is like money: we never have enough." This may seem true; however, time is not like money. One can make more money, but one cannot "make time."…

Circle, David



Frontal Plane Motion of the Pelvis and Hip during Gait Stance Discriminates Children with Diplegia Levels I and II of the GMFCS  

PubMed Central

Objective. To determine if gait waveform could discriminate children with diplegic cerebral palsy of the GMFCS levels I and II. Patients. Twenty-two children with diplegia, 11 classified as level I and 11 as level II of the GMFCS, aged 7 to 12 years. Methods. Gait kinematics included angular displacement of the pelvis and lower limb joints during the stance phase. Principal components (PCs) analyses followed by discriminant analysis were conducted. Results. PC1s of the pelvis and hip in the frontal plane differ significantly between groups and captured 80.5% and 86.1% of the variance, respectively. PC1s captured the magnitude of the pelvic obliquity and hip adduction angle during the stance phase. Children GMFCS level II walked with reduced pelvic obliquity and hip adduction angles, and these variables could discriminate the groups with a cross-validation of 95.5%. Conclusion. Reduced pelvic obliquity and hip adduction were observed between children GMFCS level II compared to level I. These results could help the classification process of mild-to-moderate children with diplegia. In addition, it highlights the importance of rehabilitation programs designed to improve pelvic and hip mobility in the frontal plane of diplegic cerebral palsy children level II of the GMFCS. PMID:22792478

Kirkwood, Renata Noce; Franco, Rosa de Lourdes Lima Dias; Furtado, Sheyla Cavalcanti; Barela, Ana Maria Forti; Deluzio, Kevin John; Mancini, Marisa Cotta



Visual-Somatosensory Integration and Balance: Evidence for Psychophysical Integrative Differences in Aging  

PubMed Central

Research detailing multisensory integration (MSI) processes in aging and their association with clinically relevant outcomes is virtually non-existent. To our knowledge, the relationship between MSI and balance has not been well-established in aging. Given known alterations in unisensory processing with increasing age, the aims of the current study were to determine differential behavioral patterns of MSI in aging and investigate whether MSI was significantly associated with balance and fall-risk. Seventy healthy older adults (M = 75 years; 58% female) participated in the current study. Participants were instructed to make speeded responses to visual, somatosensory, and visual-somatosensory (VS) stimuli. Based on reaction times (RTs) to all stimuli, participants were classified into one of two groups (MSI or NO MSI), depending on their MSI RT benefit. Static balance was assessed using mean unipedal stance time. Overall, results revealed that RTs to VS stimuli were significantly shorter than those elicited to constituent unisensory conditions. Further, the current experimental design afforded differential patterns of multisensory processing, with 75% of the elderly sample demonstrating multisensory enhancements. Interestingly, 25% of older adults did not demonstrate multisensory RT facilitation; a finding that was attributed to extremely fast RTs overall and specifically in response to somatosensory inputs. Individuals in the NO MSI group maintained significantly better unipedal stance times and reported less falls, compared to elders in the MSI group. This study reveals the existence of differential patterns of multisensory processing in aging, while describing the clinical translational value of MSI enhancements in predicting balance and falls risk. PMID:25102664

Mahoney, Jeannette R.; Holtzer, Roee; Verghese, Joe



Does sensorimotor training improve the static balance of young volleyball players?  


The aim of this investigation is to assess the effectiveness of a 6-week balance training (BT) protocol, integrated in regular training sessions, on postural sway of young female volleyball players (n = 26, age 13.0 +/- 0.2 years) divided into two groups (intervention and control; 13 per group). Trials were performed for bipedal and unipedal stance conditions before and after the BT protocol, using a pressure platform to collect center-of-pressure (COP) time series that were processed to calculate sway area, COP path length, and maximum displacement range in anteroposterior and mediolateral directions. The intervention group exhibited smaller sway areas in eyes closed conditions (intervention = 42.76 mm2, control = 67.60 mm2; p < 0.05) and Romberg quotients (intervention = 1.11 mm, control = 1.82 mm) in bipedal stance, while all the other parameters were unaffected. BT also reduced sway area (intervention = 122.70 mm2, control = 187.18 mm2) and anteroposterior COP displacements (intervention = 20.18 mm, control = 22.38 mm) of the non-dominant limb for single-leg stance. No significant change was found for the dominant limb. Although it is possible to hypothesize a beneficial effect of BT on young athletes, further investigations are required to clarify its actual effect on balance performance with respect to normal volleyball training. PMID:22518948

Pau, Massimiliano; Loi, Andrea; Pezzotta, Maria Cristina



Concepts From Time Series Michael T. Rosenstein and Paul R. Cohen  

E-print Network

Concepts From Time Series Michael T. Rosenstein and Paul R. Cohen Computer Science Department, LGRC senso- rimotor agents develop symbolic, conceptual thought, as every human child does. As in (Cohen et of the other. Epistemically, a category is simply a collection of in- stances (of objects or activities

Southern California, University of


Compatibility of postural behavior induced by two aspects of visual feedback: time delay and scale display  

Microsoft Academic Search

Fourteen healthy adults were tested to assess the potential influence on stance maintenance of two parts of the visual feedback technique (display scale and time delay). The task consisted in their keeping a spot on the screen representing their center of pressure, CoP (i.e. successive points of application of the ground reaction forces detected by the force platform on which

P. Rougier



Speeds and stance of titanosaur sauropods: analysis of Titanopodus tracks from the Late Cretaceous of Mendoza, Argentina.  


Speed estimations from trackways of Titanopodus mendozensis González Riga and Calvo provide information about the locomotion of titanosaurian sauropods that lived in South America during the Late Cretaceous. Titanopodus ichnites were found at Agua del Choique, a newly discovered track site in the Loncoche Formation, Late Campanian-Early Maastrichtian of Mendoza, Argentina. This speed study follows the hypothesis of dynamic similarity proposed by Alexander. As a refinement of this method, a complementary equation is presented here based on an articulated titanosaurian specimen collected in strata that are regarded as correlative to those that have yielded Titanopodus tracks (Allen Formation, Neuquén Basin). This analysis indicates that hip height can be estimated as 4.586 times the length of the pes track in derived titanosaurs. With an estimation of the hip height and the stride measurements, the speed is calculated. The study of two wide-gauge trackways indicates that Titanopodus ichnites were produced by medium-sized titanosaurs (hip height of 211-229 cm) that walked at 4.7-4.9 km/h towards the south and southwest, following, in part, a sinuous pathway. These speeds and some taphonomic features of tracks (prominent rims, distorted elongated shapes)indicate the capacity of derived titanosaurs for walking effectively over a very wet and slippery substrate. In the ichnological record, the walking speeds of Titanopodustrackmakers are somewhat faster than those previously inferred for most sauropods. PMID:21308347

González Riga, Bernardo J



Dynamic 3D scanning as a markerless method to calculate multi-segment foot kinematics during stance phase: methodology and first application.  


Multi-segmental foot kinematics have been analyzed by means of optical marker-sets or by means of inertial sensors, but never by markerless dynamic 3D scanning (D3DScanning). The use of D3DScans implies a radically different approach for the construction of the multi-segment foot model: the foot anatomy is identified via the surface shape instead of distinct landmark points. We propose a 4-segment foot model consisting of the shank (Sha), calcaneus (Cal), metatarsus (Met) and hallux (Hal). These segments are manually selected on a static scan. To track the segments in the dynamic scan, the segments of the static scan are matched on each frame of the dynamic scan using the iterative closest point (ICP) fitting algorithm. Joint rotations are calculated between Sha-Cal, Cal-Met, and Met-Hal. Due to the lower quality scans at heel strike and toe off, the first and last 10% of the stance phase is excluded. The application of the method to 5 healthy subjects, 6 trials each, shows a good repeatability (intra-subject standard deviations between 1° and 2.5°) for Sha-Cal and Cal-Met joints, and inferior results for the Met-Hal joint (>3°). The repeatability seems to be subject-dependent. For the validation, a qualitative comparison with joint kinematics from a corresponding established marker-based multi-segment foot model is made. This shows very consistent patterns of rotation. The ease of subject preparation and also the effective and easy to interpret visual output, make the present technique very attractive for functional analysis of the foot, enhancing usability in clinical practice. PMID:24998032

Van den Herrewegen, Inge; Cuppens, Kris; Broeckx, Mario; Barisch-Fritz, Bettina; Vander Sloten, Jos; Leardini, Alberto; Peeraer, Louis



Japan Toughens Pollution Control Stance  

ERIC Educational Resources Information Center

Special responsibility for chemical firms are delineated in three areas: (1) chemical processes that are toxic to man; (2) use best available technology to monitor the safety of effluents; (3) when any doubt of safety exists, the firm should halt operations at once and take preventive action. (DF)

Chemical and Engineering News, 1973



A time-frequency approach to estimate critical time intervals in postural control.  


The critical time interval (CTI) is a parameter that has been used to distinguish open-loop from closed-loop control during upright stance. The aim of this study was to develop a new method to determine CTIs. The new approach, termed the intermittent critical time interval (ICTI) method, was motivated from evidence that upright standing is an intermittent rather than an asymptotic stability control process. For this ICTI method, center-of-pressure time series are first transformed to the time-frequency domain with a wavelet method. Subsequently, the CTI is assumed equal to the time span between two local maxima in the time-frequency domain within a distinct frequency band (i.e., 0.5-1.1 Hz). This new method may help facilitate better estimates of the transition time interval between open and closed-loop control during upright stance and can also be applied in future work such as in simulating postural control. In addition, this method can be used in future work to assess temporal changes in CTIs. PMID:25105745

Zhang, Hongbo; Nussbaum, Maury A; Agnew, Michael J



Precueing time but not direction of postural perturbation induces early muscular activation: Comparison between young and elderly individuals.  


In this study, we evaluated the effect of precueing characteristics of an impending perturbation to upright stance on reactive responses of distal leg muscles. Young and older individuals were compared in a task of recovering stable upright stance following rotation of the supporting platform to induce anterior or posterior body sway. Directions of the supporting platform rotation were randomized across trials. Immediately before postural perturbation participants were cued about direction and/or time of platform rotation, or performed the task under directional and temporal uncertainty of the impending perturbation. Results showed that precueing time of perturbation led to earlier muscular activation onset, while precueing perturbation direction did not modulate either latency or magnitude of muscular activation. Those effects were similar between age groups. Our findings suggest that awareness of the perturbation time favored shorter response latencies in both the young and older individuals. PMID:25562634

Silva, Marina Brito; Coelho, Daniel Boari; de Lima-Pardini, Andrea Cristina; Martinelli, Alessandra Rezende; Baptista, Thais da Silva; Ramos, Renato Teodoro; Teixeira, Luis Augusto



Just-In-Time Teaching  

NSDL National Science Digital Library

The very notion of "just-in-time" teaching (JiTT) may seem to some to sound like a phrase adopted from the world of corporate culture, but in fact, it's actually a "teaching and learning strategy based on the interaction between web-based study assignments and an active learner classroom." All told, it sounds pretty compelling, and this website, created by Professor Gregor and his colleagues at Indiana University-Purdue University Indianapolis (IUPUI) has been designed to provide fellow educators with materials that will help them adopt such an educational stance and approach in the classroom. After reading the introductory section titled "What is JiTT?", visitors may wish to proceed to look over the resources area, where they can look over JiTT resources that may be used with a variety of disciplines, including physics, psychology, and chemistry.



Time-varying characteristics of visually induced postural sway.  


To study potential time-varying dynamics of postural sway as measured via center-of-pressure (COP) under the feet, we applied time-frequency analysis to COP data from ten vestibularly impaired subjects and 13 nonimpaired controls, during quiet stance and in response to visual perturbation. This analysis revealed that 1) the spectral characteristics of COP change over time; 2) there are time-dependent and frequency-dependent differences in COP between impaired and nonimpaired populations during visual perturbation, and 3) there is no difference in COP during quiet stance (eyes opne) between impaired and nonimpaired populations for the parameters investigated. A novel finding of this research is that controls appear to adapt to constant frequency visual perturbation, while vestibularly impaired subjects do not. This difference could not have been observed with conventional Fourier analysis, which is commonly used in COP data analysis, because time is not a parameter of the spectrum and adaptation is, by nature, a time-varying process. These results suggest that time-frequency analysis of COP data is useful for studying temporal dynamics of postural control, and in particular the differences between vestibularly impaired subjects and healthy controls during visual perturbation. PMID:8973968

Loughlin, P J; Redfern, M S; Furman, J M



Fall Risk-Relevant Functional Mobility Outcomes in Dementia Following Dyadic Tai Chi Exercise  

PubMed Central

Whether persons with dementia benefit from fall prevention exercise is unclear. Applying the Positive Emotion-Motivated Tai Chi protocol, preliminary findings concerning adherence and effects of a dyadic Tai Chi exercise program on persons with Alzheimer’s disease (AD) are reported. Using pre/ posttest design, 22 community-dwelling AD-caregiver dyads participated in the program. Fall-risk-relevant functional mobility was measured using Unipedal Stance Time (UST) and Timed Up and Go (TUG) tests. Results showed that 19/22 (86.4%) AD patients completed the 16-week program and final assessment; 16/19 dyads (84.2%) completed the prescribed home program as reported by caregivers. UST adjusted mean improved from 4.0 to 5.1 (Week 4, p < .05) and 5.6 (Week 16, p < .05); TUG improved from 13.2 to 11.6 (Week 4, p < .05) and 11.6 (Week 16, p > .05) post intervention. Retaining dementia patients in an exercise intervention remains challenging. The dyadic Tai Chi approach appears to succeed in keeping AD-caregiver dyads exercising and safe. PMID:22517441

Yao, Lan; Giordani, Bruno J.; Algase, Donna L.; You, Mei; Alexander, Neil B.



Asymmetric Sensory Reweighting in Human Upright Stance  

PubMed Central

To investigate sensory reweighting as a fundamental property of sensor fusion during standing, we probed postural control with simultaneous rotations of the visual scene and surface of support. Nineteen subjects were presented with pseudo-random pitch rotations of visual scene and platform at the ankle to test for amplitude dependencies in the following conditions: low amplitude vision: high amplitude platform, low amplitude vision: low amplitude platform, and high amplitude vision: low amplitude platform. Gain and phase of frequency response functions (FRFs) to each stimulus were computed for two body sway angles and a single weighted EMG signal recorded from seven muscles. When platform stimulus amplitude was increased while visual stimulus amplitude remained constant, gain to vision increased, providing strong evidence for inter-modal reweighting between vision and somatosensation during standing. Intra-modal reweighting of vision was also observed as gains to vision decreased as visual stimulus amplitude increased. Such intra-modal and inter-modal amplitude dependent changes in gain were also observed in muscular activity. Gains of leg segment angle and muscular activity relative to the platform, on the other hand, showed only intra-modal reweighting. That is, changing platform motion amplitude altered the responses to both visual and support surface motion whereas changing visual scene motion amplitude did not significantly affect responses to support surface motion, indicating that the sensory integration scheme between somatosensation (at the support surface) and vision is asymmetric. PMID:24959665

Logan, David; Kiemel, Tim; Jeka, John J.



Narrative Theory and the Intentional Stance  

Microsoft Academic Search

Drawing on treatments of the problem of intentionality in fields encompassed by the umbrella discipline of cognitive science, including language theory, psychology, and the philosophy of mind, this paper explores issues underlying recent debates about the role of intentions in narrative contexts. To avoid entering the debate on the terms set by antiintentionalists, my analysis shifts the focus away from

David Herman



Time After Time  

NSDL National Science Digital Library

Students use a variety of strategies and techniques to develop an understanding of telling time. They use estimation to tell time, using seconds, hours, and minutes in order to choose reasonable time estimates for given activities. Students use pictures, words, and symbols in order to read, write, and represent time to the nearest minute. Students determine elapsed time when given a start time, counting up using minutes and hours.

Service, National S.



Automatic classification of time-frequency plots applied to the center-of-pressure rotational components.  


Time-frequency plots are widely applied to the non-stationary analysis of signals. These plots may be difficult to interpret, particularly when large data sets have to be considered. The aim of this work is to propose an automatic procedure of feature selection and clustering to be applied to time-frequency plots. We focus on the application of this procedure to plots obtained from a non-stationary analysis of the center-of-pressure signals acquired in upright bipedal stance. From a data set of 168 time-frequency plots we obtained 5 different clusters, each characterized by a few distinctive features. We were able to interpret the results of the clustering relating them to the physiological mechanisms underlying postural sway. PMID:24110663

Chiaramello, E; Agostini, V; Balestra, G; Knaflitz, M



Telling Time  

NSDL National Science Digital Library

Practice telling time with these fun games and activities! Match the time on the clocks with this game! Match the clocks game! Primary Games Match the Clocks Tell time with a dragon. Stop the clock! Make the right time! Time to the Hour Quiz Time Test Time to the Minute Quiz Practice telling what time it will be later. Elapsed Time Work on Elapsed Time Test your skills with the Matching Elapsed Time Game ...

Lerdahl, Miss



Black time … white time: My time … your time  

Microsoft Academic Search

Indigenous time began with the Era of Creation. White time began with the invention of the calendar, sundial and clock. White time was, and still is, influenced by the calendar, clock or watch. Time to go to sleep, time to get up, time to go to work...go home, time for dinner and time to watch the football or cricket. Even




Exercise intensity progression for exercises performed on unstable and stable platforms based on ankle muscle activation.  


Ankle sprains are a common sports injury. The literature focuses on the application of neuromuscular training for the improvement of balance, injury prevention and rehabilitation. However, there is a dearth of knowledge about the appropriate prescription of exercises using unstable platforms and surfaces. The purpose of this study was to devise an ankle rehabilitation or training program with exercise progression based on the extent of muscle activation, employing platforms with different levels of stability and additional resistance. A descriptive study of electromyography (EMG) during ankle exercises was performed with a convenience sample of healthy subjects. Forty-four subjects completed 12 exercises performed in a random order. Exercises were performed unipedally or bipedally with or without elastic tubing as resistance on various unstable (uncontrolled multiaxial and uniaxial movement) and stable surfaces. Surface EMG from the tibialis anterior (TA), peroneus longus (PL) and soleus (SOL) were collected to quantify the amount of muscle activity. Significant differences were found between exercise conditions for PL (p<.001), TA (p=.011), and SOL (p<.001). The greatest EMG activity for all muscles occurred with an upright unipedal stance on a soft stability surface with resistance. The least EMG activity for the TA and SOL were in a seated position and for the PL in an erect bipedal position without resistance. Based on the level of ankle muscle activation, exercises for the ankle should progress from bilateral exercises on exercise balls (lowest intensity), to a unipedal position on a soft surface in combination with elastic tubing (highest intensity) in order to achieve progressively greater ankle muscle activation. PMID:23999147

Borreani, Sebastien; Calatayud, Joaquin; Martin, Julio; Colado, Juan Carlos; Tella, Victor; Behm, David



SYMBOLS FOR TIME = time variable  

E-print Network

SYMBOLS FOR TIME = time variable t = time now, T = target date T* = modeling limit (t=forever) Cost spent to build variation point i at time i = index over variation points #12;SYMBOLS FOR TIME = time variable t = time now, T = target date T* = modeling limit (t=forever) ...adjusted by a factor

Duchowski, Andrew T.


Reaction times  

Microsoft Academic Search

Reviews 11 studies dealing with reaction times (1910-1911). Reaction time has been utilized to study a variety of problems. The studies indicate that accurate results can not be obtained without careful attention to the technique of the method of reaction time. The topics covered include effect of intensity of stimulus on reaction time, rapidity of perception of sound and light

Herbert Woodrow



Virtual time  

Microsoft Academic Search

Virtual time is a new paradigm for organizing and synchronizing distributed systems which can be applied to such problems as distributed discrete event simulation and distributed database concurrency control. Virtual time provides a flexible abstraction of real time in much the same way that virtual memory provides an abstraction of real memory. It is implemented using the Time Warp mechanism,

David R. Jefferson



Timing matters.  


Cells are entities in space and time. Systems biology strives to understand their composition, structural organization as well as dynamic behavior under different conditions. Here, measures for dynamic properties such as characteristic times, time hierarchy and time-dependent response are reviewed. Using a number of examples from yeast and micro-organism systems biology, the importance of considering the timing in experimental and theoretical research is discussed. PMID:19941864

Klipp, Edda



Elapsed Time  

NSDL National Science Digital Library

This interactive Java applet allows the user to practice finding elapsed time using analog or digital clocks. Using the "See" mode the user advances a clock from the beginning time to the ending time and the applet calculates the elapsed time. Using the "Guess" mode, the user must calculate the elapsed time between the given beginning and ending times. Three difficulty levels allow the user to practice with hour, five minute, or single minute increments. An optional scoring feature allows the user to keep track of number correct, though this feature is optional.



Universal Time  

NSDL National Science Digital Library

This is a lesson plan for an activity that explores time zone math. Learners will translate their local time to times in other zones around the world and work with the concept of Universal Time, specifically in reference to the reporting, description and analysis of solar flares and coronal mass ejections. This is activity 10 from Exploring Magnetism Guide 3: Magnetic Mysteries of the Aurora educator guide.


Modelling Time  

E-print Network

We briefly review two concepts of time - the usual time associated with "being" and more recent ideas, answering to the description of "becoming". The approximation involved in the former is examined. Finally we argue that it is (unpredictable) fluctuations that underlie time.

Burra G. Sidharth



Geologic Time.  

ERIC Educational Resources Information Center

One of a series of general interest publications on science topics, the booklet provides those interested in geologic time with an introduction to the subject. Separate sections discuss the relative time scale, major divisions in geologic time, index fossils used as guides for telling the age of rocks, the atomic scale, and the age of the earth.…

Newman, William L.


Reaction Time  

NSDL National Science Digital Library

In this activity, learners explore reaction time and challenge themselves to improve their coordination. Do you want to move faster? Catch that ball that you never seem to see in time? Use a simple test to help you improve your reaction (or response) time.

Science, New Y.



Telling Time  

NSDL National Science Digital Library

Help your child learn how to tell time on a digital and analog clock. Practice Telling Time with this fun game! Then, match the apple clock with the digital clock to show the correct Time! Finally, is it A.M. or P.M.? Practice with this fun game! ...

Popwell, Ms.



Making Time  

ERIC Educational Resources Information Center

This article presents several tips that teachers can use to teach children about time. One activity, investigating 24-hour time, aims to familiarise upper primary students with converting a.m. and p.m. notations to 24-hour time. Another activity requires students to construct a calendar month in order to familiarize themselves with the components…

Gorham, Gail; Bobis, Janette



Time Honoured  

ERIC Educational Resources Information Center

The vast majority of literature and practices in environmental education focuses on places and spaces. Little attention has been paid to time and temporalities as elements of environments, and the ways in which how we experience time affects our experience of place. This paper is an examination of the ways in which reflection on time can be…

Campbell, Mora; Timmerman, Peter



Pleasure, Learning, Video Games, and Life: The Projective Stance  

ERIC Educational Resources Information Center

This article addresses three questions. First, what is the deep pleasure that humans take from video games? Second, what is the relationship between video games and real life? Third, what do the answers to these questions have to do with learning? Good commercial video games are deep technologies for recruiting learning as a form of profound…

Gee, James Paul



Ratite Footprints and the Stance and Gait of Mesozoic Theropods  

Microsoft Academic Search

Footprints of the rhea (Rhea ameriama) are identical in several diagnostic features to tridactyl footprints of the Mesozoic Era attributed to theropod dinosaurs. Of par- ticular interest,'(i) the rhea's feet are placed very close to its body midline as it walks, so that it virtually places one foot in front of the other; (ii) its middle toe (digit III), the



Reasons Given by UK Churchgoers for Their Stance on Evolution  

ERIC Educational Resources Information Center

A sample of 661 churchgoers from a range of Christian denominations in the United Kingdom was asked about Darwinian evolution (defined as the common origin of all species, including humans). Respondents were categorised as those who accepted the idea, those who rejected it, and those who were unsure or neutral. People in each category were given a…

Village, Andrew; Baker, Sylvia



Links between Parents' Epistemological Stance and Children's Evidence Talk  

ERIC Educational Resources Information Center

Recent experimental research highlights young children's selectivity in learning from others. Little is known, however, about the patterns of information that children actually encounter in conversations with adults. This study investigated variation in parents' tendency to focus on testable evidence as a way to answer science-related questions…

Luce, Megan R.; Callanan, Maureen A.; Smilovic, Sarah



Toward an Intercultural Stance: Teaching German and English through Telecollaboration  

ERIC Educational Resources Information Center

We discuss the challenges of Web-based teaching for language teachers and then describe in detail an extended episode of misunderstanding that occurred between 2 students discussing their versions of history during a classroom-based, asynchronous telecollaborative project between learners of German in the United States and learners of English in…

Ware, Paige D.; Kramsch, Claire



Assessing muscle stiffness from quiet stance in Parkinson's disease  

Microsoft Academic Search

In previous studies, we developed a postural stiffness mea- sure that is extracted from foot center-of-pressure (COP) trajectories from quietly standing individuals and is based on an analytical mechanical model of posture control. Here we apply this measure to patients with Parkinson's disease (PD). We correlated the postural stiffness measure with different clinical rating scales, obtained from patients. Kendall's rank

Michael Lauk; Carson C. Chow; Lewis A. Lipsitz; Susan L. Mitchell; James J. Collins



Place-Based Education: A Transformative Activist Stance  

ERIC Educational Resources Information Center

The ethnography presented by van Eijck and Roth focuses on the activities of people involved in a government funded internship program in conservation and restoration, which was offered by a "multidisciplinary research center" through a local First Nation adult education center. The internship was designed, in partnership with a local non-profit…

Coughlin, Christine A.; Kirch, Susan A.



Human Genetic Engineering: A Survey of Student Value Stances  

ERIC Educational Resources Information Center

Assesses the values of high school and college students relative to human genetic engineering and recommends that biology educators explore instructional strategies merging human genetic information with value clarification techniques. (LS)

Wilson, Sara McCormack; And Others



SEN Students' Inclusion in Greece: Factors Influencing Greek Teachers' Stance  

ERIC Educational Resources Information Center

The present study, based on recent research in secondary education schools in Greece, aimed at recording Greek teachers' attitudes towards inclusion and determining the factors that enhance positive attitudes or negative ones. The findings of this research confirm that Greek teachers, despite obvious infrastructural and institutional hindrances,…

Koutrouba, Konstantina; Vamvakari, Malvina; Theodoropoulos, Helen



Dialogic Teaching: Talk in Service of a Dialogic Stance  

ERIC Educational Resources Information Center

We consider what it means to be a dialogic teacher as characterized by Paulo Freire and Robin Alexander, and utilizing discourse analysis, we explicate how one elementary teacher's talk reflects these characteristics. We provide context for and analysis of a seven-minute discussion selected as a cumulative achievement the focal nine-year-olds are…

Boyd, Maureen Patricia; Markarian, William C.



Illuminating a dialectical transformative activist stance in education  

NASA Astrophysics Data System (ADS)

In this essay I comment on Stetsenko's (2008) essay that draws together the work of Vygotsky, Piaget and Dewey, as she attempts to counter the `new' reductionist synthesis in public educational policy. While this theoretical work is helpful, it could be enhanced further by illuminating everyday practices of learners. I pose some questions that might provoke ongoing discussions by researchers as they transform collaboratively cultural-historical activity theory.

Ritchie, Stephen M.



Illuminating a Dialectical Transformative Activist Stance in Education  

ERIC Educational Resources Information Center

In this essay I comment on Stetsenko's (2008) essay that draws together the work of Vygotsky, Piaget and Dewey, as she attempts to counter the "new" reductionist synthesis in public educational policy. While this theoretical work is helpful, it could be enhanced further by illuminating everyday practices of learners. I pose some questions that…

Ritchie, Stephen M.



Developing an Assessment Stance in Primary Art Education in England  

Microsoft Academic Search

Many English primary teachers find the notion of assessing children's work in art difficult. This paper reports on work carried out with non?art?specialist primary teachers’ and student teachers’ use of a three?point assessment model and related tasks, which supported teachers and students to engage critically with children's development, or lack of it, in observational drawing. This enabled teachers and students

Jean Gilbert



Morality and Foreign Policy. A Symposium on President Carter's Stance.  

ERIC Educational Resources Information Center

This monograph contains a critical examination of President Carter's view on ethics and foreign policy as expressed in his commencement speech at Notre Dame University on May 22, 1977. The book is organized into three parts. Part 1 contains Mr. Carter's speech entitled, "Power for Humane Purposes." Part 2 contains nine responses to the speech:…

Lefever, Ernest W., Ed.


Quantum Time  

E-print Network

Normally we quantize along the space dimensions but treat time classically. But from relativity we expect a high level of symmetry between time and space. What happens if we quantize time using the same rules we use to quantize space? To do this, we generalize the paths in the Feynman path integral to include paths that vary in time as well as in space. We use Morlet wavelet decomposition to ensure convergence and normalization of the path integrals. We derive the Schr\\"odinger equation in four dimensions from the short time limit of the path integral expression. We verify that we recover standard quantum theory in the non-relativistic, semi-classical, and long time limits. Quantum time is an experiment factory: most foundational experiments in quantum mechanics can be modified in a way that makes them tests of quantum time. We look at single and double slits in time, scattering by time-varying electric and magnetic fields, and the Aharonov-Bohm effect in time.

John Ashmead



Time Machine  

NSDL National Science Digital Library

In this lesson students will experience how geological and biological events have occurred in a clear sequence of vast but measured time. Students are taken on a simulated voyage backward in time, to the beginning of our planet. They witness that beginning, the origin of life, and a number of key events leading to the present. This becomes a dramatic experience, involving body and mind, helping students to relate physically at least to the relative timing of events in geological and biological history, if not to the absolute vastness of that time.

Larry Flammer


Geologic Time  

NSDL National Science Digital Library

The Earth is very old -- 4.5 billion years or more -- according to recent estimates. This vast span of time, called geologic time by earth scientists, is difficult to comprehend in the familiar time units of months and years, or even centuries. How then do scientists reckon geologic time, and why do they believe the Earth is so old? A great part of the secret of the Earth's age is locked up in its rocks, and our centuries-old search for the key led to the beginning and nourished the growth of geologic science.

Newman, William L.



Geologic time  

USGS Publications Warehouse

The Earth is very old 4 1/2 billion years or more according to recent estimates. This vast span of time, called geologic time by earth scientists, is difficult to comprehend in the familiar time units of months and years, or even centuries. How then do scientists reckon geologic time, and why do they believe the Earth is so old? A great part of the secret of the Earth's age is locked up in its rocks, and our centuries-old search for the key led to the beginning and nourished the growth of geologic science.

Newman, William L.



Clock Time  

NSDL National Science Digital Library

You will have practice reading the time on a clock and pairing it up with its digital or written text match. Complete this as quickly as you can in order to beat the clock! Stop the Clock 1 Stop the Clock 2 Stop the Clock 6 Each of these links varies in degree of difficulty. They progressively go up in difficulty in the time you are telling. The first starts out telling time in half hour intervals. The following activity progress to fifteen minutes. The final activity is matching up the time on the clock to ...

Miss Greene



Time interpolator  

NASA Astrophysics Data System (ADS)

A time interpolator for the measurement of time difference using digital and analog techniques is described. Emitter Coupled Logic (ECL) and high frequency techniques were used. The difficulty with ECL is to keep the connections as short as possible and to properly terminate the output to avoid reflections. The digital part of the interpolator consists of a continuous clock and logic which converts the input signal into a start and stop signal. The analog part consists of a time to amplitude converter and an analog to digital convertor. The maximum measuring time is 6.4 microns with a 100 ps resolution.

Deblok, M.



Geological Time  

NSDL National Science Digital Library

"Why do engineers need to know about geologic time?" That question is answered in this resource from the University of Saskatchewan's Department of Civil and Geological Engineering. Provided here is a discussion of the concepts of geological time; relative dating methods, such as correlation; and absolute dating methods, such as radiometric methods. Diagrams and charts are included to demonstrate these complex concepts.



Virtual Time  

Microsoft Academic Search

Virtual time is a broad, new paradigm for organizing and synchronizing distributed systems, subsuming such heretofore distantly related problems as distributed discrete event simulation and distributed database concurrency control. It is an abstraction of real time in much the same way that virtual memory is an abstraction of real memory, and it reorganizes the concepts of concurrency and synchronization in

David Jefferson



Turnover Time  

EPA Science Inventory

Ecosystems contain energy and materials such as carbon, nitrogen, phosphorus, and water, and are open to their flow-through. Turnover time refers to the amount of time required for replacement by flow-through of the energy or substance of interest contained in the system, and is ...


Time Clocks  

NSDL National Science Digital Library

This exercise can be used to demonstrate changes in the Earth through time, and the length of time it took for those changes to take place. A list of Important Dates in Earth History is provided that contains the dates of the events shown on a time clock. The teacher can pick events from the list of key events and calculate (or have students calculate) the time for the key events they wish to use. A page-size image of the clock can be printed and turned into an overhead transparency. To better demonstrate the changes since the beginning of the Paleozoic Era, the same exercise could be done the second day of class, using only the last 570 million years of time.

Greb, Stephen


Screen Time  

NSDL National Science Digital Library

This game asks you a series of questions about how much time you spend in front of a screen, not being active. It begins by pointing out that since we spend a lot of time in front of computer screens at work or school, additional time at home can really affect how healthy we are. It asks how much time you spend watching TV, playing computer games, and using the computer each day. It then adds up the total amount of screen time you spend every day, and calculates how many hours you spend a year in front of a screen. It also tells you if that's a healthy amount, and suggests ways to stay active while in front of screens.




On Time  

NSDL National Science Digital Library

This online exhibit from a prominent American museum explores the character of time -- its impact on our daily lives and its ability to shape and reform human consciousness. The site is from the National Museum of American History and concentrates on how humans have measured time from 1700 to the present. The exhibit presents text and images describing the history of keeping time from the century immediately preceding the industrial revolution -- when sundials were still in use -- to our present age of digital access and a global village that never sleeps.


Statistical Parametric Mapping (SPM) for alpha-based statistical analyses of multi-muscle EMG time-series.  


Multi-muscle EMG time-series are highly correlated and time dependent yet traditional statistical analysis of scalars from an EMG time-series fails to account for such dependencies. This paper promotes the use of SPM vector-field analysis for the generalised analysis of EMG time-series. We reanalysed a publicly available dataset of Young versus Adult EMG gait data to contrast scalar and SPM vector-field analysis. Independent scalar analyses of EMG data between 35% and 45% stance phase showed no statistical differences between the Young and Adult groups. SPM vector-field analysis did however identify statistical differences within this time period. As scalar analysis failed to consider the multi-muscle and time dependence of the EMG time-series it exhibited Type II error. SPM vector-field analysis on the other hand accounts for both dependencies whilst tightly controlling for Type I and Type II error making it highly applicable to EMG data analysis. Additionally SPM vector-field analysis is generalizable to linear and non-linear parametric and non-parametric statistical models, allowing its use under constraints that are common to electromyography and kinesiology. PMID:25465983

Robinson, Mark A; Vanrenterghem, Jos; Pataky, Todd C



Time outs  


... Time-out technique for discipline. Children's Health Network web site. ... a break from negative behavior. Massachusetts Medical Society web site. ...


Time Management  

NSDL National Science Digital Library

This section of Mind Tools teaches you time management skills. These are the simple, practical techniques that have helped the leading people in business, sport and public service reach the pinnacles of their careers.

MindTools (MindTools)



Creative Time  

NSDL National Science Digital Library

Creative Time curates, funds, and organizes public art projects, so their website is a reference of the form dating back to 1975. You can browse by program name, date or artist's name (the most common of these being "multiple artists.") Creative Time's roster also includes familiar names such as Marina Abramovic, Doug Aitken, Laurie Anderson, David Byrne, Paul Chan, Jenny Holzer, Gary Hume, Vik Muniz, Takashi Murakami, Shirin Neshat, Steve Powers, and Cai Guo-Qiang. For example, Creative Time worked with Cai Guo-Qiang to present Light Cycle, in 2003, to celebrate the 150th anniversary of New York City's Central Park; in 2008 David Byrne's Playing the Building transformed the Battery Maritime Building in Lower Manhattan into a massive sound sculpture that visitors could play using a keyboard; and in summer 2012 Creative Time and multiple artists hosted a sandcastle competition at Far Rockaway, possibly the start of a new New York summer tradition.



Bleeding time  


Bleeding time is a blood test that looks at how fast small blood vessels in the skin close to stop you from bleeding. ... deep enough to cause a tiny amount of bleeding. The blood pressure cuff is immediately deflated. Blotting ...


About time  

NASA Technical Reports Server (NTRS)

Time has historically been a measure of progress of recurrent physical processes. Coordination of future actions, prediction of future events, and assigning order to events are three practical reasons for implementing clocks and signalling mechanisms. In large networks of computers, these needs lead to the problem of synchronizing the clocks throughout the network. Recent methods allow this to be done in large networks with precision around 1 millisecond despite mean message exchange times near 5 milliseconds. These methods are discussed.

Denning, Peter J.



Wuda Time  

NSDL National Science Digital Library

The Wuda Time project management tool is designed to help individuals keep track of their dedication to various tasks and operations. Visitors can sign up right on the site to have instant access to this powerful tool. It's easy to use and users can prioritize certain tasks with a color-coded system or designate certain task completion times. This version is compatible with all operating systems.


Time 100  

NSDL National Science Digital Library

This Time Warner Pathfinder (discussed in the November 11, 1994 Scout Report) Time Magazine site, released to coincide with a Time cover story of the same title, is the first in what is to be a five part site that will eventually cover 100 of the 20th Century's most influential people. At present the site contains profiles of 20 of the century's most influential "leaders & revolutionaries," including Margaret Sanger, Vladimir Lenin, Winston Churchill, Dr. Martin Luther King, Jr., Ayatolla Ruholla Khomeini, and the anonymous Chinese protester who blocked the tank in the Tienanmen Square protest in 1989. Stories about the personalities by such authors as Gloria Steinem, Arthur Schlesinger, Jr., Salman Rushdie, Elie Wiesel, and Stanley Karnow, among others, highlight the site. There is also a timeline of each personality, as well as a timeline of the century. For the personalities who were covered by Time, an original in-depth story from the Time archives is available. Forthcoming throughout 1998 and 1999 are sections on "entertainers & artists, builders & titans, scientists & thinkers, and heroes and inspirations." The site is also available in a Shockwave Flash version.



Reaction Time  

NSDL National Science Digital Library

In this activity, learners conduct an experiment to test how fast they can react. Learners try to catch a piece of paper with a ruler printed on it (or a ruler) as quickly as they can. Learners collect data and compare the reaction times of friends and family.

Boston, Wgbh



Deep Time  

NSDL National Science Digital Library

In this video a Penn State professor refers to National Park canyons carved out by water and wind as he explains “deep time” - the notion that the earth is billions of years old; another professor states how the theory of evolution is supported by evidence of an ancient Earth recorded in rocks.




Reaction Time  

NSDL National Science Digital Library

This lab is not an inquiry activity. There are some students whose reaction times will not allow them to catch a 12 inch ruler. They may use a dowel, stick, strip of cardboard, etc. Although the students are led to believe that the point of the lab is to

Horton, Michael



Geologic Time  

NSDL National Science Digital Library

This site contains 24 questions on the topic of geologic time, which covers dating techniques and unconformities. This is part of the Principles of Earth Science course at the University of South Dakota. Users submit their answers and are provided immediate feedback.

Heaton, Timothy


Geological Time  

Microsoft Academic Search

IN his Presidential Address to Section C at Dover, Sir A. Geikie has offered a bold challenge to Lord Kelvin and those who agree with him by calling upon them to give due weight to geological phenomena in forming an estimate of geological time. Permit me to say what I think about it.

O. Fisher



Split belt treadmill with differential velocity and biofeedback for well-balanced gait of patient with stroke  

Microsoft Academic Search

A split belt treadmill robot for gait rehabilitation was developed to improve the symmetry of the stance phase time of patients with stroke. The system, which increases the stance phase time of the affected leg and then realizes a well-balanced gait, is divided into two components. First, the stance phase of the unaffected (“sound”) and affected legs is measured and

Takeshi Ando; Eiichi Ohki; Yasutaka Nakashima; Yutaka Akita; Hiroshi Iijima; Osamu Tanaka; Masakatsu G. Fujie



Bilingual Education: An Idea Whose Time Has Come.  

ERIC Educational Resources Information Center

Bilingual education is not entirely a new idea. In the 18th and 19th centuries it was practiced in church schools, particularly in German and Spanish. Most communities, however, assumed a strongly assimilationist stance for their public schools, especially after World War I. In recent years, however, this attitude has been partly reversed under…

Shaw, Frederick



Time Traveler  

NSDL National Science Digital Library

This NOVA website simulates travel to distant stars and back in a spaceship that can move at various percentages of the speed of light. You set the spaceship speed and choose your destination star, and the simulation calculates the time of travel as measured on Earth and inside the spaceship. Text describes the "twin paradox" of the theory of relativity and also the 1971 test of its prediction using airliners and atomic clocks.



Female Team Overall Name Age Rank Time Rank Time Rank Time Pace Rank Time Rank Time Pace Time  

E-print Network

Female Team Overall Name Age Rank Time Rank Time Rank Time Pace Rank Time Rank Time Pace Time 1 Amy:56:27.6 Deborah Mc Eligot Deborah Storrings Male Team Overall Name Age Rank Time Rank Time Rank Time Pace Rank Time Rank Time Pace Time 1 Macon Fessenden 20 1 5:42.2 2 0:26.9 1 34:29.7 3:23 1 0:12.8 1 17:41.1 3

Suzuki, Masatsugu


A robust real-time gait event detection using wireless gyroscope and its application on normal and altered gaits.  


Gait events detection allows clinicians and biomechanics researchers to determine timing of gait events, to estimate duration of stance phase and swing phase and to segment gait data. It also aids biomedical engineers to improve the design of orthoses and FES (functional electrical stimulation) systems. In recent years, researchers have resorted to using gyroscopes to determine heel-strike (HS) and toe-off (TO) events in gait cycles. However, these methods are subjected to significant delays when implemented in real-time gait monitoring devices, orthoses, and FES systems. Therefore, the work presented in this paper proposes a method that addresses these delays, to ensure real-time gait event detection. The proposed algorithm combines the use of heuristics and zero-crossing method to identify HS and TO. Experiments involving: (1) normal walking; (2) walking with knee brace; and (3) walking with ankle brace for overground walking and treadmill walking were designed to verify and validate the identified HS and TO. The performance of the proposed method was compared against the established gait detection algorithms. It was observed that the proposed method produced detection rate that was comparable to earlier reported methods and recorded reduced time delays, at an average of 100 ms. PMID:25619613

Gouwanda, Darwin; Gopalai, Alpha Agape



Acute Orthotic Intervention Does Not Affect Muscular Response Times and Activation Patterns at the Knee  

PubMed Central

Objective: To evaluate the short-term effect of a semirigid foot orthotic device on response times and activation patterns of knee musculature in individuals with hyperpronation after a lower extremity perturbation in a single-leg, weight-bearing stance. Design and Setting: We used a lower extremity perturbation device designed to produce a forward and either internal or external rotation of the trunk and femur on the weight-bearing tibia to evoke a reflex response. Subjects were tested both with and without orthotic devices. Subjects: Seventeen (13 male, 4 female) volunteers (age, 20.6 ± 1.8 years; height, 181.0 ± 8.1 cm; weight, 87.4 ± 19.5 kg; navicular drop, 12.1 ± 1.8 mm) with a navicular drop greater than 10 mm volunteered for this study. Measurements: Long latency reflex times were recorded via surface electromyography for the medial and lateral hamstrings, gastrocnemius, and quadriceps muscles. Results: A dependent-sample t test revealed a significant decrease in navicular drop with orthotic intervention (P < .0001). With that confirmed, separate repeated-measures analyses of variance with 2 within factors (orthotic condition and muscle) revealed no significant difference in muscle response time between orthotic and nonorthotic conditions for either internal or external rotation perturbation. Although we found a main effect for muscle for both internal (P < .0001) and external (P < .0001) rotation, indicating a preferred muscle activation order, this activation order did not differ between orthotic and nonorthotic conditions (internal rotation P = .674, external rotation P = .829). Conclusions: Our findings suggest that a short-term application of a semirigid orthotic device does not alter muscle response times or activation patterns of the muscles that stabilize the knee. Further research is needed to determine whether changes in activation patterns may occur over time since mechanical adaptations occur with long-term wear. PMID:12937425

Rose, Holly M.; Shultz, Sandra J.; Arnold, Brent L.; Gansneder, Bruce M.; Perrin, David H.



Being, doing, knowing, and becoming: Science and opportunities for learning in the out-of-school-time setting  

NASA Astrophysics Data System (ADS)

This dissertation addresses the question of how structured out-of-school-time settings, such as afterschool programs and summer camps, are positioned to support children's engagement and learning in science. This study addresses a gap in the research literature that does not fully specify the nature of the out-of-school-time (OST) setting and that generally does not position learning and development in relationship to one another, instead focusing on one or the other. As a result of an incomplete conceptualization of the OST setting as a site for learning and development, the OST field is becoming increasingly academicized, and its developmental qualities and benefits for children are under siege. A transformative activist stance (Stetsenko, 2008) guides my goals in undertaking this study -- to produce knowledge that can inform the design and implementation of OST science programs -- and it also guides my analysis of what constitutes learning in OST science. A transformative activist stance is a perspective on cultural-historical theory that understands individual development as occurring through agentive, goal-directed efforts to change one's self and one's world. These goals and actions are always developed and enacted in cultural-historical context. Learning, which occurs through the appropriation of cultural tools and schema to achieve one's purposes, and which leads human development, is understood broadly, as entailing processes of being, doing, knowing and becoming (see Herrenkohl & Mertl, in press). I also draw on bioecological theory (Bronfenbrenner, 1979) to analyze the proximal processes that support and sustain children's participation in the OST setting. In this study, I analyze the structural, developmental, and conceptual features of three different OST science programs to understand how they create opportunities for learning and engagement in science. The contributions of this study are to better specify the nature of the OST science program setting and to better conceptualize how learning and development relate to one another in the context of OST science. I draw on my analysis to make recommendations for ways in which OST science learning can be expanded and enriched for more children in more settings.

Bevan, Bronwyn



E-print Network

1 TIME & LABOR TRAINING MANUAL TIME APPROVAL /2013 #12;2 TABLE OF CONTENTS TIME APPROVAL - THINGS TO REMEMBER ..................................................................... 3 TIME APPROVAL - QUICK GUIDE

Barrash, Warren


Time Commitments Where Does Your Time Go  

E-print Network

Time Commitments Where Does Your Time Go Everyone starts the week with the same number of hours. So, why does your time go so fast? Let's find out! Number of hours of sleep each night ____ x 7 preparation/clean-up time) ____ x 7 = ____ Travel time to and from campus ___ x __ = ____ Number of hours per

Kasman, Alex


Time Preference, Time Discounting, and Smoking Decisions  

Microsoft Academic Search

This study examines the relationship between time discounting, other sources of time preference, and intertemporal choices about smoking. Using a survey fielded for our analysis, we elicit rates of time discount from choices in financial and health domains. We also examine the relationship between other determinants of time preference and smoking status. We find very high rates of time discount

Ahmed Khwaja; Dan Silverman; Frank Sloan



Time preference, time discounting, and smoking decisions  

Microsoft Academic Search

This study examines the relationship between time discounting, other sources of time preference, and choices about smoking. Using a survey fielded for our analysis, we elicit rates of time discount from choices in financial and health domains. We also examine the relationship between other determinants of time preference and smoking status. We find very high rates of time discount in

Ahmed Khwaja; Dan Silverman; Frank Sloan



Time uncertainty in simple reaction time  

Microsoft Academic Search

Studied the relationship between reaction time and Ss' uncertainty about the time of stimulus presentation. Reaction time increases with foreperiod variability and with mean foreperiod above an optimum value less than 1 sec. The important determiner of reaction time is not the immediate foreperiod but the distribution of foreperiods within which it is embedded.

Edmund T. Klemmer



History without time: Buffon's natural history as a nonmathematical physique.  


While "natural history" is practically synonymous with the name of Buffon, the term itself has been otherwise overlooked by historians of science. This essay attempts to address this omission by investigating the meanings of "physique," "natural philosophy," and "history," among other terms, with the purpose of understanding Buffon's actual objectives. It also shows that Buffon never claimed to be a Newtonian and should not be considered as such; the goal is to provide a historical analysis that resituates Buffon's thought within his own era. This is done, primarily, by eschewing the often-studied question of time in Buffon. Instead, this study examines the nontemporal meanings of the word "history" within the naturalist's theory and method. The title of his Natural History is examined both as an indicator of the kind of science that Buffon was hoping to achieve and as a source of great misinterpretation among his peers. Unlike Buffon, many of his contemporaries actually envisioned the study of nature from a Baconian perspective where history was restricted to the mere collection of facts and where philosophy, which was the implicit and ultimate goal of studying nature, was seen, at least for the present, as unrealizable. Buffon confronts this tendency insofar as his Histoire naturelle claims to be the real physique that, along with describing nature, also sought to identify general laws and provide clear insight into what true knowledge of nature is or should be. According to Buffon, history (both natural and civil) is not analogous to mathematics; it is a nonmathematical method whose scope encompasses both nature and society. This methodological stance gives rise to the "physicization" of certain moral concepts--a gesture that was interpreted by his contemporaries as Epicurean and atheist. In addition, Buffon reduces a number of metaphysically tainted historical concepts (e.g., antediluvian monuments) to objects of physical analysis, thereby confronting the very foundation of natural theology. In Buffon, as this essay makes clear, natural history is paving the way for a new physique (science of natural beings), independent from mathematics and from God, that treats naturalia in a philosophical and "historical" manner that is not necessarily "temporal." PMID:20575489

Hoquet, Thierry



Time on Your Hands: Modeling Time  

NSDL National Science Digital Library

Building physical models relative to a concept can be an important activity to help students develop and manipulate abstract ideas and mental models that often prove difficult to grasp. One such concept is time. A method for helping students understand the cyclical nature of time involves the construction of a Time Zone Calculator through a series of physical models. This article explains how to construct a Time Zone Calculator and provides suggestions for its use.

Beaver, John; Finson, Kevin



Time Crystals from Minimum Time Uncertainty  

E-print Network

Motivated by the Generalized Uncertainty Principle, covariance, and a minimum measurable time, we propose a deformation of the Heisenberg algebra, and show that this leads to corrections to all quantum mechanical systems. We also demonstrate that such a deformation implies a discrete spectrum for time. In other words, time behaves like a crystal.

Faizal, Mir; Das, Saurya



Time Crystals from Minimum Time Uncertainty  

E-print Network

Motivated by the Generalized Uncertainty Principle, covariance, and a minimum measurable time, we propose a deformation of the Heisenberg algebra, and show that this leads to corrections to all quantum mechanical systems. We also demonstrate that such a deformation implies a discrete spectrum for time. In other words, time behaves like a crystal.

Mir Faizal; Mohammed M. Khalil; Saurya Das



'Stutter timing' for charge decay time measurement  

NASA Astrophysics Data System (ADS)

The paper describes the approach of 'stutter timing' that has been developed to improve the accuracy of measuring charge decay times in the presence of noise in compact and portable charge decay test instrumentation. The approach involves starting and stopping the timing clock as the noisy signal rises above and falls below the target threshold voltage level.

Chubb, John; Harbour, John; Pavey, Ian



Time on Your Hands: Modeling Time  

ERIC Educational Resources Information Center

Building physical models relative to a concept can be an important activity to help students develop and manipulate abstract ideas and mental models that often prove difficult to grasp. One such concept is "time". A method for helping students understand the cyclical nature of time involves the construction of a Time Zone Calculator through a…

Finson, Kevin; Beaver, John



Time Capsule Signature  

Microsoft Academic Search

We introduce a new cryptographic problem called time cap- sule signature. Time capsule signature is a 'future signature' that be- comes valid from a specific future time t, when a trusted third party (called Time Server) publishes some trapdoor information associated with the time t. In addition, time capsule signature should satisfy the following properties: (1) If the signer wants,

Yevgeniy Dodis; Dae Hyun Yum



Space time and the passage of time  

E-print Network

This paper examines the various arguments that have been put forward suggesting either that time does not exist, or that it exists but its flow is not real. I argue that (i) time both exists and flows; (ii) an Evolving Block Universe (`EBU') model of spacetime adequately captures this feature, emphasizing the key differences between the past, present, and future; (iii) the associated surfaces of constant time are uniquely geometrically and physically determined in any realistic spacetime model based in General Relativity Theory; (iv) such a model is needed in order to capture the essential aspects of what is happening in circumstances where initial data does not uniquely determine the evolution of spacetime structure because quantum uncertainty plays a key role in that development. Assuming that the functioning of the mind is based in the physical brain, evidence from the way that the mind apprehends the flow of time prefers this evolving time model over those where there is no flow of time.

George F. R. Ellis; Rituparno Goswami



Personal Time Line  

NSDL National Science Digital Library

In this activity, learners work in groups to create a time line representing significant moments in their lives. Learners use scientific suffixes and prefixes to label their time lines, modeling the Geologic Time Line (i.e. Mesozoic, Paleozoic).

Muller, Eric



Intelligence, Inspection Time, and Decision Time.  

ERIC Educational Resources Information Center

Relationships among Multidimensional Aptitude Battery scores, inspection time, choice reaction time, and the odd-man procedure were investigated for 63 female and 25 male adults. No significant relationships were found for these mental speed measures and the Eysenck Personality Questionnaire-Revised dimensions of extraversion, neuroticism, and…

Bates, Timothy C.; Eysenck, Hans J.



The Hands of Time  

NSDL National Science Digital Library

Students explore the different ways to measure time and develop their understanding of how to tell time to the hour, half and quarter hours, and then five minute intervals. They identify time on analog and digital clocks and read a clock at the hour or half hour. They participate in timed events and keep time as record keepers. In the final lesson, students make a My Time Book.

Service, National S.



On Time. 6b: Quantum Mechanical Time  

E-print Network

The existence of small amounts of advanced radiation, or a tilt in the arrow of time, makes the basic equations of physics mixed-type functional differential equations. The novel features of such equations point to a microphysical structure of time. This corresponds to a change of logic at the microphysical level. We show that the resulting logic is a quantum logic. This provides a natural and rigorous explanation of quantum interference. This structured-time interpretation of quantum mechanics is briefly compared with various other interpretations of q.m.

C. K. Raju



From Time to Time: Processing Time Reference Violations in Dutch  

ERIC Educational Resources Information Center

Time reference in Indo-European languages is marked on the verb. With tensed verb forms, the speaker can refer to the past (wrote, has written), present (writes, is writing) or future (will write). Reference to the past through verb morphology has been shown to be particularly vulnerable in agrammatic aphasia and both agrammatic and…

Dragoy, Olga; Stowe, Laurie A.; Bos, Laura S.; Bastiaanse, Roelien



Synchronized time stamp support  

SciTech Connect

New software has been added to IOC core to maintain time stamps. The new software has the ability to maintain time stamps over all IOCs on a network. The purpose of this paper is to explain how EPICS will synchronize the time stamps. In addition, this paper will explain how to configure and use the new EPICS time stamp support software.

Kowalkowski, J.



Traveling Through Time  

NSDL National Science Digital Library

This video excerpt from NOVA’s The Fabric of the Cosmos: The Illusion of Time explains gravity’s pull on time, and how time travel may be possible in the future. However, this kind of time travel might not be exactly like Hollywood’s depiction.

WGBH Educational Foundation



Time and Teaching  

ERIC Educational Resources Information Center

This essay invites reflection on the phenomena of time as it impacts the day-to-day life of teachers. It also explores assumptions about time and teaching in three areas: first, beliefs about the force of time and the teacher's struggle to control it; second, beliefs about the potential of time and the benefits of its passing for teachers and…

McEwan, Anna E.



Did time begin? Will time end?  

E-print Network

Did time begin at a Big Bang? Will the present expansion of the universe last for a finite or infinite time? These questions sound philosophical but are becoming, now in the twenty-first century, central to the scientific study of cosmology. The answers, which should become clarified in the next decade or two, could have profound implications for how we see our own role in the universe. Since the original publication of Stephen Hawking's {\\it A Brief History of Time} in 1988, the answers to these questions have progressed as a result of research by the community of active theoretical physicists including myself. To present the underlying ideas requires discussion of a wide range of topics in cosmology, especially the make up of the energy content of the universe. A brief summary of my conclusions, that of three different possibilities concerning the history and future of time, the least likely is the conventional wisdom (time began and will never end) and most likely is a cyclic model (time never begins or ends), is in the short final Chapter which could be read first. To understand the reasoning leading to my conclusions could encourage reading of my entire book. My hope in writing this, my first popular book, is that it will engender reflection about time. Many a non-scientist may already hold a philosophical opinion about whether time begins and ends. This book's aim is to present some recently discovered scientific facts which can focus the reader's consideration of the two short questions in my title.

Paul H. Frampton



Tempus Fugit: Time Flies  

NSDL National Science Digital Library

This online exhibit from a prominent American museum explores the character of time -- its impact on our daily lives and its ability to shape and reform human consciousness. Tempus Fugit: Time Flies is a superb exhibit from the Nelson Atkins Museum of Art that uses items from the museum to exemplify different understandings of time. The exhibit features sections on 20th Century Time, World Times, and Conservation Time. Twentieth-century time considers the changing nature of time in the technological age by examining the innovations in graphic and plastic arts inspired by an altered sense of time. The exhibit includes works by Muybridge, Edward Hopper, Salvador Dali, Kandinsky, Rothko, Roy Lichtenstein, and others. The second section, World Times, focuses on the different conceptions of time embodied in art from primitive times to the present and ranges from ancient Native American to Medieval Europe to ancestral Africa to the deeply cosmological perceptions of time in ancient Indian civilizations. Conservation Time takes visitors behind the scenes to see how conservation science can uncover the history of a work's composition and the changes wrought upon it over the course of its lifetime. The Website also offers ideas for teaching using the exhibits. In sum, this is an elegantly constructed and intelligent Website. To be sure, users will want to set aside some time for it as the graphics enforce their own meditative pace upon the viewer.


Systematically Controlling for the Influence of Age, Sex, Hertz and Time Post-Whole-Body Vibration Exposure on Four Measures of Physical Performance in Community-Dwelling Older Adults: A Randomized Cross-Over Study  

PubMed Central

Though popular, there is little agreement on what whole-body vibration (WBV) parameters will optimize performance. This study aimed to clarify the effects of age, sex, hertz and time on four physical function indicators in community-dwelling older adults (N = 32). Participants were exposed to 2?min WBV per session at either 2?Hz or 26?Hz and outcome measures were recorded at 2, 20 and 40?min post-WBV. Timed get up-and-go and chair sit-and-reach performances improved post-WBV for both sexes, were significantly different between 2?Hz and 26?Hz treatments (P ? 0.05) and showed statistically significant interactions between age and gender (P ? 0.01). Counter movement jump and timed one-legged stance performances showed a similar but non-significant response to 2?Hz and 26?Hz treatments, though male subjects showed a distinct trended response. Age and gender should be statistically controlled and both 2?Hz and 26?Hz exert a treatment effect. PMID:21977028

Merriman, Harold L.; Brahler, C. Jayne; Jackson, Kurt



Physiologic time: A hypothesis  

NASA Astrophysics Data System (ADS)

The scaling of respiratory metabolism with body size in animals is considered by many to be a fundamental law of nature. One apparent consequence of this law is the scaling of physiologic time with body size, implying that physiologic time is separate and distinct from clock time. Physiologic time is manifest in allometry relations for lifespans, cardiac cycles, blood volume circulation, respiratory cycle, along with a number of other physiologic phenomena. Herein we present a theory of physiologic time that explains the allometry relation between time and total body mass averages as entailed by the hypothesis that the fluctuations in the total body mass are described by a scaling probability density.

West, Damien; West, Bruce J.



Universal Time Tunneling  

E-print Network

How much time does a tunneling wave packet spent in traversing a barrier? Quantum mechanical calculations result in zero time inside a barrier . In the nineties analogous tunneling experiments with microwaves were carried out. The results agreed with quantum mechanical calculations. Electron tunneling time is hard to measure being extremely short and parasitic effects due to the electric charge of electrons may be dominant. However, quite recently the atomic ionization tunneling time has been measured. Experimental data of photonic, phononic, and electronic tunneling time is available now and will be presented. It appears that the tunneling time is a universal property independent of the field in question.

Guenter Nimtz



Verification of timing routines  

SciTech Connect

A method for verifying the validity of timing routines for benchmarking and other timing measurements at the Los Alamos Scientific Laboratory (LASL) is described. A program written for this purpose uses two methods. The first method compares stopwatch times and system-computed times, where a system-computed time is the result of a call to the system timing routine. The second method requires calculating elapsed machine cycles. The program is modular and uses standard Fortran. With only a few changes, it is possible across all LASL systems and can be used on non-LASL systems as well. A complete benchmark job mix should include a program of this type.

Creel, L.R.



Precision Pulsar Timing  

NASA Astrophysics Data System (ADS)

P140 continues to set new standards in precision timing, in terms of both the quality and quantity of pulsars timed at the sub-microsecond level. Recent highlights include highest precision timing (74 ns), the best relative timing (pulsar versus pulsar) of 200 ns, new parallaxes, DM variations and outstanding astrometry. P140 has been conducted for more than ten years. We propose to continue this experiment, improving timing methodologies and precision. This unprecedented precision timing baseline provides exciting opportunities to investigate the existence and level of any Gravitational Wave Background and allows pulsar astrometric parameter estimations with unprecedented accuracies in astronomy.

Bailes, Matthew; Ord, Stephen; Manchester, Dick; Verbiest, Joris P. W.; Bhat, Ramesh; Hotan, Aidan; Kulkarni, S. R.; Jacoby, Bryan; Teoh, Albert



Physiologic time: a hypothesis.  


The scaling of respiratory metabolism with body size in animals is considered by many to be a fundamental law of nature. One apparent consequence of this law is the scaling of physiologic time with body size, implying that physiologic time is separate and distinct from clock time. Physiologic time is manifest in allometry relations for lifespans, cardiac cycles, blood volume circulation, respiratory cycle, along with a number of other physiologic phenomena. Herein we present a theory of physiologic time that explains the allometry relation between time and total body mass averages as entailed by the hypothesis that the fluctuations in the total body mass are described by a scaling probability density. PMID:23659904

West, Damien; West, Bruce J



Timing system observations  

SciTech Connect

The purpose of this document is to augment Synchronized Time Stamp Support authored by Jim Kowalkowski. This document provides additional documentation to clarify and explain software involved in timing operations of the accelerator.

Winans, J.



Infinite Time Turing Machines  

Microsoft Academic Search

Infinite time Turing machines extend the operation of ordinary Turing machines into transfinite ordinal time. By doing so, they provide a natural model of infinitary computability, a theoretical setting for the analysis of the power and limitations of supertask algorithms.

Joel David Hamkins



Screen time and children  


"Screen time" is a term used for activities done in front of a screen, such as watching TV, working on a computer, or playing video games. Screen time is sedentary activity, meaning you are being physically ...


Time and Relativity  

NSDL National Science Digital Library

This video from the American Museum of Natural History illustrates Einstein's special theory of relativity and the relationship between time and the motion of objects, including the concept of time dilation.

Foundation, Wgbh E.



Geologic Time: Online Edition  

NSDL National Science Digital Library

Offered by the United States Geological Survey (USGS) as a general interest publication, this site is an online edition of a text by the same name, offering a concise overview of the concepts associated with the age of the Earth. The online edition was revised in October of 1997 to reflect current thinking on this topic. Section headers are Geologic Time, Relative Time Scale, Major Divisions of Geologic Time, Index Fossils, Radiometric Time Scale, and Age of the Earth.



Is It about Time?  

Microsoft Academic Search

The theme for the 2008 Social Science History Association conference was “It’s about Time.” By surveying the program and panels on offer in Miami, the presidential address instead asked, “Is it about time?” Location and space figured more centrally than time in the titles of the conference’s many papers. Still, two conceptions of time were prominent features of the program.

Donna R. Gabaccia



Timing verification and the timing analysis program  

Microsoft Academic Search

Timing Verification consists of validating the path delays (primary input or storage element to primary output or storage element) to be sure they are not too long or too short and checking the clock pulses to be sure they are not too wide or too narrow. The programs addressing these problems neither produce input patterns like test pattern generators nor

Robert B. Hitchcock



Timing Verification and the Timing Analysis program  

Microsoft Academic Search

Timing Verification consists of validating the path delays (primary input or storage element to primary output or storage element) to be sure they are not too long or too short and checking the clock pulses to be sure they are not too wide or too narrow. The programs addressing these problems neither produce input patterns like test pattern generators nor

Robert B. Hitchcock Sr.



Discrete time techniques for time delay estimation  

Microsoft Academic Search

Basic aspects of time delay estimation (TDE) based on sampled signals are investigated. The direct cross-correlation method is analyzed and compared to the average square difference function (ASDF) and the (addition only based) average magnitude difference function (AMDF) estimators, Their relative accuracy is theoretically evaluated, and previous empirical results are explained. It is shown that both the ASDF- and the

Giovanni Jacovitti; Gaetano Scarano



The Myth of Time.  

ERIC Educational Resources Information Center

This paper offers a variety of approaches to teaching the concept of time. Many social studies courses traditionally emphasize time as measured by clocks and as useful for recording when events occur in relation to each other. In addition to this approach, the author suggests that students should reflect upon four other modes of time. These are…

Hantula, James


Time-periodic universes  

E-print Network

In this letter we construct a new time-periodic solution of the vacuum Einstein's field equations whose Riemann curvature norm takes the infinity at some points. We show that this solution is intrinsically time-periodic and describes a time-periodic universe with the "black hole". New physical phenomena are investigated and new singularities are analyzed for this universal model.

De-Xing Kong; Kefeng Liu; Ming Shen



Real-Time Databases  

Microsoft Academic Search

Data in real-time databases has to be logically consistent as well as temporally consistent. The latter arises from the need to preserve the temporal validity of data items that reflect the state of the environment that is being controlled by the system. Some of the timing constraints on the transactions that process real-time data come from this need. These constraints,

Krithi Ramamritham



Noncommutative Two Time Physics  

E-print Network

We present a classical formalism describing two-time physics with Abelian canonical gauge field backgrounds. The formalism can be used as a starting point for the construction of an interacting quantized two-time physics theory in a noncommutative soace-time.

W. Chagas-Filho



Time Service Department  

NSDL National Science Digital Library

This site from the US Navy is the official source of time for the Department of Defense (DoD) and the Global Positioning System (GPS), and a Standard of Time for the United States. It features numerous links to other useful time and GPS-related sites.

Navy, U. S.


Time Is Money  

ERIC Educational Resources Information Center

One has heard it before: time is money, especially when it comes to adding time for instruction to the school day. When budgets are tight and relief is nowhere in sight, how can schools afford to implement a reform as costly as adding instructional time? It's a daunting task, yet current federal educational priorities tied to federal funding…

Oxley, Diana; Baete, Glenn



Finding Structure in Time  

Microsoft Academic Search

Time underlies many interesting human behaviors. Thus, the question of how to represent time in connectionist models is very important. One approach is to represent time implicitly by its effects on processing rather than explicitly (as in a spatial representation). The current report develops a proposal along these lines first described by Jordan (1986) which involves the use of recurrent

Jeffrey L. Elman



Euglobulin lysis time  


Euglobulin lysis time (ELT) is a blood test that looks at how fast clots break down in the blood. ... A longer-than-normal ELT time may be due to: Diabetes Prematurity A shorter-than-normal ELT time may be due to: Blood vessel injury or surgery ...


Introduction Flipping time distribution  

E-print Network

Introduction The model Flipping time distribution A model genetic switch with feedback Paolo Visco distribution Outline 1 Introduction 2 The model 3 Flipping time distribution Paolo Visco A model genetic switch with feedback #12;Introduction The model Flipping time distribution Outline 1 Introduction 2 The model 3

Visco, Paolo - Laboratoire Matière et Systèmes Complexes, Université Paris 7


Pulsar timing array  

NASA Astrophysics Data System (ADS)

Simultaneous timing of several pulsars distributed over the sky, so called Pulsar Timing Array (PTA), is used for a variety of metrological and astronomical applications. Three examples of PTA application are presented: link between celestial reference frames, ensemble pulsar time scale and detection of gravitational waves.

Rodin, Alexander E.



Absolute Time Derivatives  

E-print Network

A four dimensional treatment of nonrelativistic space-time gives a natural frame to deal with objective time derivatives. In this framework some well known objective time derivatives of continuum mechanics appear as Lie-derivatives. Their coordinatized forms depends on the tensorial properties of the relevant physical quantities. We calculate the particular forms of objective time derivatives for scalars, vectors, covectors and different second order tensors from the point of view of a rotating observer. The relation of substantial, material and objective time derivatives is treated.

T. Matolcsi; P. Van



A time representation  

E-print Network

The paper contains a proposal for an energy and time representation. We construct modes that correspond to fuzzy distributions around discrete values of energy or time. The modes form an orthogonal and complete set in the space of square integrable functions. Energy and time are self adjoint in the space spanned by the modes. The widths of the modes are analyzed as well as their energy-time uncertainty relations. The lower uncertainty attainable for the modes is shown. We also show times of arrival for massless particles.

Lucas Lamata; Juan Leon




E-print Network

This essay examines our fundamental conceptions of time, spacetime, the asymmetry of time, and the motion of a quantum mechanical particle. The concept of time has multiple meanings and these are often confused in the literature and must be distinguished if any light is to be thrown on this age-old issue. The asymmetry of time also has different meanings that depend on context-although the fundamental time asymmetry is associated with the expansion of the universe. These and related issues are discussed in both classical and quantum mechanical contexts.

Gerald E. Marsh



Big Time Tour  

NSDL National Science Digital Library

In this activity (on pages 16-21), learners get a sense of geological time by understanding how big a million is. Part One of the activity is the "Million Appreciation Lesson," which puts a million seconds, names in a phone book, and hiked steps into more familiar units. Part Two is "Investigating All Time," where learners make a time line for the history of the Earth using the length of their own arm to represent the total 4.5 billion year long scale. They mark major time zones, such as the age of the dinosaurs, at appropriate lengths along the time line.

Museum, University O.; Nebraska Cooperative Extension 4-H Youth Development



Modeling Geologic Time  

NSDL National Science Digital Library

In this activity students convert major events in Earth history from years before present into scale distances. After a list of events and their scale distances have been formulated, students construct a geologic time scale on 5 meters of adding machine paper, beginning with the formation of the Earth. Students will investigate change through geologic time; design, construct and interpret a model of geologic time; relate major events in Earth history to the geologic time scale; and compare and relate the span of Earth history to events of historical time and of the human lifetime. Some sample events and their approximate relative ages are included.

Firebaugh, James


Time scales in LISA  

E-print Network

The LISA mission is a space interferometer aiming at the detection of gravitational waves in the [$10^{-4}$,$10^{-1}$] Hz frequency band. In order to reach the gravitational wave detection level, a Time Delay Interferometry (TDI) method must be applied to get rid of (most of) the laser frequency noise and optical bench noise. This TDI analysis is carried out in terms of the coordinate time corresponding to the Barycentric Coordinate Reference System (BCRS), TCB, whereas the data at each of the three LISA stations is recorded in terms of each station proper time. We provide here the required proper time versus BCRS time transformation. We show that the difference in rate of station proper time versus TCB is of the order of $5 10^{-8}$. The difference between station proper times and TCB exhibits an oscillatory trend with a maximum amplitude of about $10^{-3}$ s.

S. Pireaux



Biomarker time out.  


The advancement of knowledge relies on scientific investigations. The timing between asking a question and data collection defines if a study is prospective or retrospective. Prospective studies look forward from a point in time, are less prone to bias and are considered superior to retrospective studies. This conceptual framework conflicts with the nature of biomarker research. New candidate biomarkers are discovered in a retrospective manner. There are neither resources nor time for prospective testing in all cases. Relevant sources for bias are not covered. Ethical questions arise through the time penalty of an overly dogmatic concept. The timing of sample collection can be separated from testing biomarkers. Therefore the moment of formulating a hypothesis may be after sample collection was completed. A conceptual framework permissive to asking research questions without the obligation to bow to the human concept of calendar time would simplify biomarker research, but will require new safeguards against bias. PMID:24557857

Petzold, Axel; Bowser, Robert; Calabresi, Paolo; Zetterberg, Henrik; Uitdehaag, Bernard M J



Time card entry system  

SciTech Connect

The Time Card Entry System was developed to interface with the DOE Headquarters Electronic Time and Attendance (ETA) system. It features pop-up window pick lists for Work Breakdown Structure Numbers and Hour Codes and has extensive processing that ensures that time and attendance reported by the employee fulfills US Government/OMB requirements before Timekeepers process the data at the end of the two week payroll cycle using ETA. Tours of Duty (e.g. ten hour day, four day week with Friday through Sunday off), established in the ETA system, are imported into the Time Card Entry System by the Timekeepers. An individual`s Tour of Duty establishes the basis for validation of time of day and number of hours worked per day. At the end of the two week cycle, data is exported by the Timekeepers from the Time Card Entry System into ETA data files.

Montierth, B.S.



On Time Performance Pressure  

NASA Technical Reports Server (NTRS)

Within many operations, the pressures for on-time performance are high. Each month, on-time statistics are reported to the Department of Transportation and made public. There is a natural tendency for employees under pressure to do their best to meet these objectives. As a result, pressure to get the job done within the allotted time may cause personnel to deviate from procedures and policies. Additionally, inadequate or unavailable resources may drive employees to work around standard processes that are seen as barriers. However, bypassing practices to enable on-time performance may affect more than the statistics. ASRS reports often highlight on-time performance pressures which may result in impact across all workgroups in an attempt to achieve on-time performance. Reporters often provide in-depth insights into their experiences which can be used by industry to identify and focus on the implementation of systemic fixes.

Connell, Linda; Wichner, David; Jakey, Abegael



Matter: Space without Time  

E-print Network

While Quantum Gravity remains elusive and Quantum Field Theory retains the interpretational difficulties of Quantum Mechanics, we have introduced an alternate approach to the unification of particles, fields, space and time, suggesting that the concept of matter as space without time provides a framework which unifies matter with spacetime and in which we anticipate the development of complete theories (ideally a single unified theory) describing observed 'particles, charges, fields and forces' solely with the geometry of our matter-space-time universe.

Yousef Ghazi-Tabatabai



It's About Time  

NSDL National Science Digital Library

In past times, ocean navigators tossed a piece of wood over the side of their ships and noted how long until the ship passed the wood. They used this time measurement and the length of the ship to calculate their speed and estimate how far they had traveled. In this activity, students act the part of a GPS signal traveling to the receiver to learn how travel time is converted to distance.

Integrated Teaching And Learning Program


Geologic Time Discussion Analogies  

NSDL National Science Digital Library

The slides provide a fun way of discussing the immensity of geologic time and help to grasp the age of the earth, the time gaps between major geologic events, and the relative minuteness of humans time on earth. After the discussion with the class, students are given opportunity to develop their own analogies using "everyday" things (other than the calendar and money examples used in this activity).

Noah Fay


Bleeding time in preeclampsia.  


The association of preeclampsia with thrombocytopenia and prolonged bleeding time is reported. The analysis of bleeding time (Simplate II) and the platelet count (Automatic Coulter Counter) in 41 patients with different grades of preeclampsia is presented. Our results suggest that the decrease in the bleeding time observed in moderate preeclampsia and the increase observed in severe preeclampsia are not mainly dependent on the platelet count. PMID:7976241

Ivankovic, M; Pereira, J; Bianchi, M; Germain, A; Mezzano, D



Space-time gestures  

Microsoft Academic Search

A method for learning, tracking, and recognizing human gestures using a view-based approach to model articulated objects is presented. Objects are represented using sets of view models, rather than single templates. Stereotypical space-time patterns, i.e., gestures, are then matched to stored gesture patterns using dynamic time warping. Real-time performance is achieved by using special purpose correlation hardware and view prediction

Trevor Darrell; Alex Pentland



Making Time for Feedback  

ERIC Educational Resources Information Center

Ask any teacher what he or she needs more of, and it is a good bet that time will top the list. Anything that promises to recoup a little bit of their workday time is sure to be a best seller. One overlooked time-saver is in how they use feedback. Teachers know that feedback is important for teaching and learning. Unfortunately, most secondary…

Fisher, Douglas; Frey, Nancy



What is Geologic Time?  

NSDL National Science Digital Library

This webpage of the National Park Service (NPS) and United States Geological Survey (USGS) discusses geologic time and what it represents. Beginning about 4.6 billion years ago and ending in the present day, this site exhibits (to scale) the various eras, periods, eons, and epochs of Earth's history with a downloadable geologic time scale available. Links provide maps of what the Earth looked like at various times in its history, as well as a description of how scientists developed the time scale and how they know the age of the Earth.


Fields of Time  

NSDL National Science Digital Library

This outdoor exercise shows students the great expanse of time that has elapsed between the formation of Earth and the emergence of living creatures, particularly humans. The great length of the football field helps reinforce the idea of the vast amounts of time that have passed. Starting on one goal line, they will mark off distances representing the times of various events, rocks, fossils, or geologic eras. The teacher can calculate the distances needed, or students can do it themselves in the classroom. A table is provided to help convert distances in yards to time in millions of years, and links to additional information are included.

Greb, Stephen


Intrinsic Time Quantum Geometrodynamics  

E-print Network

Quantum Geometrodynamics with intrinsic time development and momentric variables is presented. An underlying SU(3) group structure at each spatial point regulates the theory. The intrinsic time behavior of the theory is analyzed, together with its ground state and primordial quantum fluctuations. Cotton-York potential dominates at early times when the universe was small; the ground state naturally resolves Penrose's Weyl Curvature Hypothesis, and thermodynamic and gravitational `arrows of time' point in the same direction. Ricci scalar potential corresponding to Einstein's General Relativity emerges as a zero-point energy contribution. A new set of fundamental commutation relations without Planck's constant emerges from the unification of Gravitation and Quantum Mechanics.

Eyo Eyo Ita III; Chopin Soo; Hoi-Lai Yu



Manage Your Time  

E-print Network

by deciding how to use it, and which activities will benef_it us most. B-6049 6-00 Some people think of time management as ?putting first things first.? Others think of it as doing things efficiently. Time management is self-management. ?You can?t master... your time this way. . . Number of Hours Activity 8 Work (Job) 3 Personal Work 2 Personal Fun 11 Personal Maintenance your chart will look like the one below. When you have an accurate picture of how you use your time, decide which activi- ties were most...

White, Lynn



A Walk Through Time  

NSDL National Science Digital Library

The Physics Laboratory of the National Institute of Standards and Technology (NIST) provides A Walk Through Time, a site devoted to examining the question of how humans have measured time throughout history. In one example, Egyptians created the first timepiece (shadow clock or sundial) in the approximate year of 1500 BC to measure "hours." Nowadays, the Physics Laboratory develops and operates the "standards of time and frequency and coordinates them with other world standards." Those interested in timekeeping methods and an historical perspective on the evolution of time measurement will find this site fascinating.


Time functions as utilities  

E-print Network

Every time function on spacetime gives a (continuous) total preordering of the spacetime events which respects the notion of causal precedence. The problem of the existence of a (semi-)time function on spacetime and the problem of recovering the causal structure starting from the set of time functions are studied. It is pointed out that these problems have an analog in the field of microeconomics known as utility theory. In a chronological spacetime the semi-time functions correspond to the utilities for the chronological relation, while in a K-causal (stably causal) spacetime the time functions correspond to the utilities for the K^+ relation (Seifert's relation). By exploiting this analogy, we are able to import some mathematical results, most notably Peleg's and Levin's theorems, to the spacetime framework. As a consequence, we prove that a K-causal (i.e. stably causal) spacetime admits a time function and that the time or temporal functions can be used to recover the K^+ (or Seifert) relation which indeed turns out to be the intersection of the time or temporal orderings. This result tells us in which circumstances it is possible to recover the chronological or causal relation starting from the set of time or temporal functions allowed by the spacetime. Moreover, it is proved that a chronological spacetime in which the closure of the causal relation is transitive (for instance a reflective spacetime) admits a semi-time function. Along the way a new proof avoiding smoothing techniques is given that the existence of a time function implies stable causality, and a new short proof of the equivalence between K-causality and stable causality is given which takes advantage of Levin's theorem and smoothing techniques.

E. Minguzzi



Time Functions as Utilities  

NASA Astrophysics Data System (ADS)

Every time function on spacetime gives a (continuous) total preordering of the spacetime events which respects the notion of causal precedence. The problem of the existence of a (semi-)time function on spacetime and the problem of recovering the causal structure starting from the set of time functions are studied. It is pointed out that these problems have an analog in the field of microeconomics known as utility theory. In a chronological spacetime the semi-time functions correspond to the utilities for the chronological relation, while in a K-causal (stably causal) spacetime the time functions correspond to the utilities for the K + relation (Seifert’s relation). By exploiting this analogy, we are able to import some mathematical results, most notably Peleg’s and Levin’s theorems, to the spacetime framework. As a consequence, we prove that a K-causal (i.e. stably causal) spacetime admits a time function and that the time or temporal functions can be used to recover the K + (or Seifert) relation which indeed turns out to be the intersection of the time or temporal orderings. This result tells us in which circumstances it is possible to recover the chronological or causal relation starting from the set of time or temporal functions allowed by the spacetime. Moreover, it is proved that a chronological spacetime in which the closure of the causal relation is transitive (for instance a reflective spacetime) admits a semi-time function. Along the way a new proof avoiding smoothing techniques is given that the existence of a time function implies stable causality, and a new short proof of the equivalence between K-causality and stable causality is given which takes advantage of Levin’s theorem and smoothing techniques.

Minguzzi, E.



The Measurement of Time  

E-print Network

We present a definition of time measurement based on high energy photons and the fundamental length scale, and show that, for macroscopic time, it is in accord with the Lorentz transformation of special relativity. To do this we define observer in a different way than in special relativity.

A. Boyarsky; P Gora



Scheduling with Slack Time  

Microsoft Academic Search

We consider a scheduling problem concerning a set of jobs {J1, J2,..., Jn} in which the job Ji requests Ci units of computation time every Ti units of time periodically. These jobs are to be executed by a timeshared single-processor computing system. It is assumed that the requests for each job arrive at the system at the beginning of the

C. L. Liu; Jane W.-S. Liu; Arthur L. Liestman



Time Series Data Library  

NSDL National Science Digital Library

This is a collection of time series datasets covering many application areas, but are all for time series analysis. Some of the topics covered are: agriculture, chemistry, crime, demography, ecology, finance, health, hydrology, industry, labor market, macroeconomics, physics, production, sales, sport, transportation, tourism, tree rings and utilities. The data are in text format, thus they can be used without any additional software.

Hyndman, Robert



Time division multiplexing  

Microsoft Academic Search

The characteristics of time division multiplexing are explained for both pulse amplitude modulation and pulse code modulation systems. An analysis of word synchronization in asynchronous numerical multiplexing is included. The hierarchy in numerical multiplexing is discussed. The strategy for frame aligning, frame dimensioning, and the jitter of waiting time are treated. Bibtex entry for this abstract Preferred format for this

M. Decina; C. Rossi



Managing Your Time  

NSDL National Science Digital Library

"A year from now you will wish you had started today." --Karen Lamb Your Schedule Doesn't Lie One of the best ways to evaluate your priorities is to keep a time journal. A time journal is a basic breakdown of every hour in your week. Write down how many ...

Center, Wsu'S S.



Geologic Time Online Edition  

NSDL National Science Digital Library

This tutorial will help students learn and understand the concepts of geologic time and the age of the Earth. They will investigate the geologic time scale and learn about the use of index fossils and radiometric dating to determine the age of rock formations and fossils.


Where in Time?  

NSDL National Science Digital Library

This engaging activity helps students construct their own understanding of Earth's history and understand the geologic time scale. While working through the activity, students learn science concepts related to geologic time and the value of cooperation and effective communication. The lesson is aligned to the following National Science Education Standards: Science as Inquiry, Earth's History, and the Nature of Science.

David Sacks



Water Molecule Residence Times  

NSDL National Science Digital Library

How long will a molecule of Water stay in a particular reservoir? What is the average time a molecule of Water will stay in an ocean? What is the average time a molecule of water will stay in a river? A lake? As groundwater? A glacier? How long will a water vapor molecule stay suspended in the atmosphere? Why is the residence ...

Science, Sill -.



Estimating Distance and Time  

NSDL National Science Digital Library

Students learn to estimate the time it takes to travel different distances based on an estimation of the time it takes to travel a part of the whole route. This reinforces basic fractional/ratio thinking, as well as early multiplication as repeated addition.




Distance-Time Graphs  

NSDL National Science Digital Library

The representation is an animated slide show which: -describes a distance-time graph -explains what the slope of a distance time graph represents -explains its usefulness in understanding an objects motion This resource also includes an interactive test and review of the material, and can be downloaded for offline use.


TTVFast: Transit timing inversion  

NASA Astrophysics Data System (ADS)

TTVFast efficiently calculates transit times for n-planet systems and the corresponding radial velocities. The code uses a symplectic integrator with a Keplerian interpolator for the calculation of transit times (Nesvorny et al. 2013); it is available in both C and Fortran.

Deck, Katherine; Agol, Eric; Holman, Matt; Nesvorny, David



Timely Warning Update  

ERIC Educational Resources Information Center

A complaint received by the Department of Education alleged that Virginia Tech violated the "timely warning" requirements of the Clery Act on April 16, 2007, by not issuing specific campus-wide alerts once senior officials knew of the immediate threat to health and safety. The complaint also alleged that the University's timely warning policy, as…

Stafford, Dolores



Time Here, Time There, Time Everywhere: Teaching Young Children Time through Daily Routine  

ERIC Educational Resources Information Center

According to Piaget, 5- or 6-year-old children gradually acquire the concept of time based on events (Piaget, 1969). In his experiment of investigating children's time concepts, Piaget found that children of these ages were able to place pictures based on sequential events with some errors; the younger children made more errors. The National…

Lee, Joohi; Lee, Joo Ok; Fox, Jill



Survivability Versus Time  

NASA Technical Reports Server (NTRS)

Develop Survivability vs Time Model as a decision-evaluation tool to assess various emergency egress methods used at Launch Complex 39B (LC 39B) and in the Vehicle Assembly Building (VAB) on NASAs Kennedy Space Center. For each hazard scenario, develop probability distributions to address statistical uncertainty resulting in survivability plots over time and composite survivability plots encompassing multiple hazard scenarios.

Joyner, James J., Sr.



Time - A Traveler's Guide  

NASA Astrophysics Data System (ADS)

"Bucky Fuller thought big," Wired magazine recently noted, "Arthur C. Clarke thinks big, but Cliff Pickover outdoes them both." In his newest book, Cliff Pickover outdoes even himself, probing a mystery that has baffled mystics, philosophers, and scientists throughout history--What is the nature of time?In Time: A Traveler's Guide , Pickover takes readers to the forefront of science as he illuminates the most mysterious phenomenon in the universe--time itself. Is time travel possible? Is time real? Does it flow in one direction only? Does it have a beginning and an end? What is eternity? Pickover's book offers a stimulating blend of Chopin, philosophy, Einstein, and modern physics, spiced with diverting side-trips to such topics as the history of clocks, the nature of free will, and the reason gold glitters. Numerous diagrams ensure readers will have no trouble following along.By the time we finish this book, we understand a wide variety of scientific concepts pertaining to time. And most important, we will understand that time travel is, indeed, possible.

Pickover, Clifford A.



Time for Reform.  

ERIC Educational Resources Information Center

Integral to school restructuring is the need to create time for school staff to participate in developing a vision, setting goals, formulating plans, training, and exchanging experiences. The use of time is both the object of and the chief impediment to change. The study surveyed educational literature, and business management journals,…

Purnell, Susanna; Hill, Paul


Predicting chaotic time series  

Microsoft Academic Search

A forecasting technique for chaotic data is presented. After a time series has been embedded in a state space using delay coordinates, the induced nonlinear mapping is 'learned' using a local approximation. This makes it possible to make short-term predictions of the future behavior of a time series, using information based only on past values. An error estimate is presented

J. Doyne Farmer; John J. Sidorowich



Measuring entrepreneurship over time  

Microsoft Academic Search

This article is a review of three measurement issues that impact the study of entrepreneurship over time: (1) level of analysis difference between firms and individuals, (2) differences between rate and stock measures, and (3) the effects of choosing particular time frames on subsequent analytical results. Based on theory that views entrepreneurship as depending on ownership rights (Hawley 1907), this

Scott A. Shane



Modelling bursty time series  

NASA Astrophysics Data System (ADS)

Many human-related activities show power-law decaying interevent time distribution with exponents usually varying between 1 and 2. We study a simple task-queuing model, which produces bursty time series due to the non-trivial dynamics of the task list. The model is characterized by a priority distribution as an input parameter, which describes the choice procedure from the list. We give exact results on the asymptotic behaviour of the model and we show that the interevent time distribution is power-law decaying for any kind of input distributions that remain normalizable in the infinite list limit, with exponents tunable between 1 and 2. The model satisfies a scaling law between the exponents of interevent time distribution (?) and autocorrelation function (?): ? + ? = 2. This law is general for renewal processes with power-law decaying interevent time distribution. We conclude that slowly decaying autocorrelation function indicates long-range dependence only if the scaling law is violated.

Vajna, Szabolcs; Tóth, Bálint; Kertész, János



Athlete support personnel and anti-doping: Knowledge, attitudes, and ethical stance.  


Athlete support personnel (ASP) failing to meet responsibilities under the World Anti-Doping Code risk sanction. It is unclear whether the poor knowledge of responsibilities seen in sports physicians and coaches applies to other ASP (e.g., administrators, chiropractors, family, nutritionists, physiotherapists, psychologists, and trainers). A purposive sample of Australian ASP (n?=?292) responded to a survey on knowledge of anti-doping rules (35 true/false questions), ethical beliefs and practice, and attitudes toward performance enhancement. Some ASP declined to participate, claiming doping was irrelevant to their practice. Physicians were most knowledgeable (30.8/35), with family and trainers the least (26.0/35). ASP reported that improvements were needed to support anti-doping education (e.g., basis for anti-doping) and practice (e.g., rules). ASP also had a slightly negative attitude toward performance enhancement. Linear regression showed that being a sports physician, providing support at the elite level, and 15 years of experience influenced knowledge. The results confirm gaps in knowledge, suggesting that stronger engagement with ASP anti-doping education and practice is needed. Applying the principles of andragogy could help foster active engagement through emphasis on active inquiry, rather than passive reception of content. Future work on the context within which ASP experience anti-doping is needed, exploring acquisition and translation of knowledge into practice. PMID:23692367

Mazanov, J; Backhouse, S; Connor, J; Hemphill, D; Quirk, F



Ideologies of Violence: A Corpus and Discourse Analytic Approach to Stance in Threatening Communications  

ERIC Educational Resources Information Center

This authentic threat asserts impending fatal injury. Because of the dangerous nature of threats, investigators must immediately ask: Is the intent real? Is the threatener likely to act? With real lives at risk, using the linguistic information available to answer these questions quickly and accurately is of great importance. Yet, because most…

Gales, Tammy Angela



Constructing Identities through "Discourse": Stance and Interaction in Collaborative College Writing  

ERIC Educational Resources Information Center

There has been little research on academic writers that shows how social interaction influences the construction of "discoursal identity" (the impressions that writers convey about themselves in their texts and that readers develop about writers). This study analyzes a collaborative writing session among college students to explore the negotiation…

Olinger, Andrea R.



Teachers' Stances and Practical Arguments regarding a Science-Indigenous Knowledge Curriculum: Part 1  

ERIC Educational Resources Information Center

The new South African curriculum known as Curriculum 2005 (to depict the year of its full implementation) requires that teachers integrate school science with Indigenous Knowledge Systems (IKS). Curriculum 2005 has generated heated debates at various levels since its inception in 1997. This study focuses on the effectiveness or otherwise of a…

Ogunniyi, M. B.



Teachers’ Stances and Practical Arguments Regarding a Science?Indigenous Knowledge Curriculum: Part 1  

Microsoft Academic Search

The new South African curriculum known as Curriculum 2005 (to depict the year of its full implementation) requires that teachers integrate school science with Indigenous Knowledge Systems (IKS). Curriculum 2005 has generated heated debates at various levels since its inception in 1997. This study focuses on the effectiveness or otherwise of a Practical Argumentation Course (PAC) as an instructional tool

M. B. Ogunniyi



Estimation of Quasi-Stiffness of the Human Knee in the Stance Phase of Walking  

E-print Network

data characterizing the quasi-stiffness of lower-limb joints during human locomotion is limited gait speed, knee excursion, and subject height and weight. Then, based on the identified key variables, we used experimental walking data for 136 conditions (speeds of 0.75­2.63 m/s) across 14 subjects

Dollar, Aaron M.


Postural steadiness during quiet stance does not associate with ability to recover balance in older women  

Microsoft Academic Search

BackgroundFall risk depends on ability to maintain balance during daily activities, and on ability to recover balance following a perturbation such as a slip or trip. We examined whether similar neuromuscular variables govern these two domains of postural stability.

Dawn C. Mackey; Stephen N. Robinovitch



Effects of body lean and visual information on the equilibrium maintenance during stance  

Microsoft Academic Search

Maintenance of equilibrium was tested in conditions when humans assume different leaning postures during upright standing.\\u000a Subjects (n=11) stood in 13 different body postures specified by visual center of pressure (COP) targets within their base of support\\u000a (BOS). Different types of visual information were tested: continuous presentation of visual target, no vision after target\\u000a presentation, and with simultaneous visual feedback

Marcos Duarte; Vladimir M. Zatsiorsky



Posture-movement responses to stance perturbations and upper limb fatigue during a repetitive pointing task.  


Localized muscle fatigue and postural perturbation have separately been shown to alter whole-body movement but little is known about how humans respond when subjected to both factors combined. Here we sought to quantify the kinematics of postural control and repetitive upper limb movement during standing surface perturbations and in the presence of fatigue. Subjects stood on a motion-based platform and repetitively reached between two shoulder-height targets until noticeably fatigued (rating of perceived exertion=8/10). Every minute, subjects experienced a posterior and an anterior platform translation while reaching to the distal target. Outcomes were compared prior to and with fatigue (first vs. final minute data). When fatigued, regardless of the perturbation condition, subjects decreased their shoulder abduction and increased contralateral trunk flexion, a strategy that may relieve the load on the fatiguing upper limb musculature. During perturbations, kinematic adaptations emerged across the trunk and arm to preserve task performance. In contrast to our expectation, the kinematic response to the perturbations did not alter in the presence of fatigue. Kinematic adaptations in response to the perturbation predominantly occurred in the direction of the reach whereas fatigue adaptations occurred orthogonal to the reach. These findings suggest that during repetitive reaching, fatigue and postural perturbation compensations organize so as to minimize interaction with each other and preserve the global task characteristics of endpoint motion. PMID:24054899

Fuller, Jason R; Fung, Joyce; Côté, Julie N



Two Dimensions of an Inquiry Stance toward Student-Learning Data  

ERIC Educational Resources Information Center

Background/Context: Schools and districts are increasingly emphasizing evidence-based decision making as a means for improving teaching and learning. In response, professional development efforts have shifted toward situated, sustained activities that involve groups of teachers in reflective inquiry about student learning data, instructional…

Nelson, Tamara Holmlund; Slavit, David; Deuel, Angie



Unilateral lower limb muscle fatigue induces bilateral effects on undisturbed stance and muscle EMG activities.  


The study investigated the effects of an unilateral ankle muscle fatigue onto independent postural control parameters including the trajectories of the estimated resultant CoP (CoPres) and his components: the centre of gravity (CG) and CoP-CG trajectories. Nine healthy men realized series of 10 toe-lift immediately followed by 10 knee flexions until exhaustion with one (Ex) leg. Maximal isometric voluntary contractions, postural sway measures of each leg, and muscular activities of the ankle muscles were recorded before and immediately after the fatiguing exercise. As expected, the latter induced a decrease in maximal voluntary peak force associated with a greater variability of the relative contribution of each leg on the CoPres, enhanced all postural parameters of the non-exercised leg. A significant decreased of the tibialis anterior EMG activity for the Ex leg and an increased one for the NoEx leg. Finally, following unilateral fatigue, the body sway destabilisation seemed to occur only along the medio-lateral (ML) axis. The enhanced and greater variability of the variance along ML axis might be explained by the recourse at the loading-unloading strategy choice and suggests a central attempt to compensate for pain sensation. PMID:19879160

Berger, L L; Regueme, S C; Forestier, N



Cultivating an Inquiry Stance in English Education: Rethinking the Student Teaching Seminar  

ERIC Educational Resources Information Center

We argue that the student teaching seminar, a co-requisite to student teaching, may best be construed as a "first" introduction to a teacher learning community and to inquiry-oriented professional development. Using a qualitative case study design and discourse analysis, we examine 60 "Teaching Inquiries" (TIs) occurring in student teaching…

Meyer, Tom; Sawyer, Mary



Estimation of Quasi-Stiffness of the Human Hip in the Stance Phase of Walking  

E-print Network

of North Carolina at Chapel Hill, Raleigh, North Carolina, United States of America Abstract This work Editor: Damian Christopher Genetos, University of California Davis, United States of America Received of Mechanical Engineering and Materials Science, Yale University, New Haven, Connecticut, United States

Dollar, Aaron M.


Extensive expertise in endocrinology: UK stance on adult GH replacement: the economist vs the endocrinologist.  


In the UK, through the use of a forced economic model, endocrinologists are in the curious position of offering GH replacement to some patients with severe GH deficiency (GHD) but withholding it from other patients with even more severe GHD. This approach is counter-intuitive to endocrine practice in treating endocrine deficiency states. For all other endocrine deficiencies, one would opt for treating those with the most severe biochemical evidence of deficiency first. If this endocrine approach was applied to adult GH replacement in an era of rationing, one would start with the GHD patients with a pathologically low IGF1 level. Given that the prevalence of subnormal IGF1 levels in a GHD population is age-dependent, this would result in GH replacement being offered to more young adult onset (AO) GHD and childhood onset GHD adults, and less often to middle-aged and elderly AO GHD adults. This in itself has the added advantage that the skeletal benefits appear more real in the former cohort of patients. PMID:23904274

Shalet, S M



Teachers' Emerging Stances and Repertoires towards Reconciliation: Potential and Challenges in Greek-Cypriot Education  

ERIC Educational Resources Information Center

In this paper we examine Greek-Cypriot teachers' positions towards the--largely unfamiliar--concept of reconciliation within the Greek-Cypriot community. Looking at a set of 40 interviews conducted in spring 2009, this study is set against the broader historical context of the continuing Cyprus Problem and the development of ethnic rivalry between…

Zembylas, Michalinos; Charalambous, Panayiota; Charalambous, Constadina



Exploring Literacy Coaches' Relationships with Teachers: Balancing Responsive and Directive Coaching Stances  

ERIC Educational Resources Information Center

Literacy coaching has become an increasingly popular form of literacy professional development in the United States based on the common assumption that strong relationships between coaches and teachers will drive instructional improvement and gains in student achievement. However, there is little empirical research describing how literacy coaches…

Ippolito, Jacy C.



APPS’s stance on self-plagiarism: Just say no1  

PubMed Central

Should authors be able to reuse the same text in multiple papers without citing the earlier source? Known as self-plagiarism, this practice is strongly discouraged in Applications in Plant Sciences (APPS) because it violates professional standards, is potentially deceptive, and lacks originality. The most frequent form of self-plagiarism in APPS submissions is text recycling, which depending on the extent and location of copied text, has consequences ranging from authors being required to rewrite duplicated text or add citations, to automatic rejection of a manuscript without review. Ultimately, avoidance of self-plagiarism will result in original articles that improve upon, and do not simply replicate, the existing literature. PMID:25202643

Culley, Theresa M.



Briefing paper N3-2001 The fiscal stance and economic coordination in Europe  

E-print Network

on tax cut programs during a favourable growth context? As already emphasised, a procyclical fiscal should one think of such a position? The Fiscal debate The slowdown of growth in Europe, has had the opportunity of the recent favourable growth environment to meet the target of the Stability and Growth pact

Paris-Sud XI, Université de


Is gender inclusivity an answer to ethical issues in business? An Indian stance  

Microsoft Academic Search

Purpose – If females are more ethical than males, as the literature on the subject generally suggests, engaging and encouraging females in their careers would certainly promote an ethical environment. The present paper is motivated by such a viewpoint and aims to investigate gender-based differences in the ethical disposition and the underlying dimensions in ethical decision-making processes, by specific examination

Suveera Gill



Effect of equinus foot placement and intrinsic muscle response on knee extension during stance  

E-print Network

, a common movement abnormality among individuals with stroke and cerebral palsy, is often associated or cerebral palsy [1]. The exaggerated ankle plantarflexion at initial foot contact typical of equinus gait


Market States and the Effect on Equity REIT Returns due to Changes in Monetary Policy Stance  

Microsoft Academic Search

This study investigates the effect of changes in monetary policy on US equity real estate investment trust (EREIT) returns\\u000a in lower and higher return ranges during bull, bear, and volatile stock market states using quantile regression. Results show\\u000a that EREIT returns are sensitive to changes in monetary policy at different EREIT return ranges in different market states.\\u000a During bull markets,

Ming-Chi Chen; Chi-Lu Peng; So-De Shyu; Jhih-Hong Zeng



Teachers' Stances on Cell Phones in the ESL Classroom: Toward a "Theoretical" Framework  

ERIC Educational Resources Information Center

In the ongoing and constantly expanding discussion surrounding cell phones in the classroom, a theoretical complement to the practical side of the issue is generally lacking. This is perhaps understandable. Many teachers are still trying to deal with the simple presence of cell phones in the class, and managing a classroom in which the presence…

Brown, Jeff



Using a Video-Based Curriculum to Develop a Reflective Stance in Prospective Mathematics Teachers  

ERIC Educational Resources Information Center

Although video cases are increasingly being used in teacher education as a means of situating learning and developing habits of reflection, there has been little evidence of the outcomes of such use. This study investigates the effects of using a coherent video-case curriculum in a university mathematics methods course by addressing two issues:…

Stockero, Shari L.



Lethality and Autonomous Robots: An Ethical Stance Ronald C. Arkin and Lilia Moshkina  

E-print Network

of lethality in warfare. As part of an ARO-funded study, we are currently investigating the points of view frameworks. Under the assumption that warfare, unfortunately and inevitably, will continue into the foreseeable future in different guises, the question arises as to how will the advent of autonomous systems


Is the Personal Political? Chronotopes and Changing Stances toward Catalan Language and Identity  

ERIC Educational Resources Information Center

During the early catalanization of schooling in the Barcelona area in the 1980s, Castilian-speaking teenagers of working-class immigrant descent often struggled against Catalan language and identity. This longitudinal study followed a group of high-school classmates and found that as young adults, some but not all of the resistant working-class…

Woolard, Kathryn A.



John Tooby & Leda Cosmides6 SubStance # 94/95, 2001  

E-print Network

: The Anomaly of the Arts in the Evolutionary Landscape Organic evolution has two independent components, which by the stochastic components of evolution--for example, genetic drift appears 6 #12;Does Beauty Build Adapted Minds, sexual jealousy, the avoidance of incest, the formation of in-groups, and hundreds of other major

Cosmides, Leda


Taking a Stance through Visual Texts: Novice Teachers as Educational Agents  

ERIC Educational Resources Information Center

Drawing on qualitative methodologies that integrate verbal and non-verbal texts, this study investigated novice teachers' attributions of their experiences of internship, as conveyed through a visual text. Novices were invited to design a visual text that represented their experience during internship, as part of a national call entitled…

Orland-Barak, Lily; Maskit, Ditza



Effects of asymmetrical stance and movement on body rotation in pushing.  


Pushing objects in the presence of body asymmetries could increase the risk of back injury. Furthermore, when the object is heavy, it could exacerbate the effects induced by asymmetrical posture. We investigated how the use of asymmetrical posture and/or upper extremity movement affect vertical torque (Tz) and center of pressure (COP) displacement during pushing. Ten healthy volunteers were instructed to push objects of three different weights using two hands (symmetrical hand use) or one hand (asymmetrical hand use) while standing in symmetrical or asymmetrical foot-positions. The peak values of Tz and COP displacement in the medial-lateral direction (COPML) were analyzed. In cases of isolated asymmetry, changes in the Tz were mainly linked with effects of hand-use whereas effects of foot-position dominated changes in the COPML displacement. In cases of a combined asymmetry, the magnitudes of both Tz and COPML were additive when asymmetrical hand-use and foot-position induced the rotation of the lower and upper body in the same direction or subtractive when asymmetries resulted in the rotation of the body segments in the opposite directions. Moreover, larger Tz and COP displacements were seen when pushing the heavy weight. The results point out the importance of using Tz and COPML to describe the isolated or combined effects of asymmetrical upper extremity movement and asymmetrical posture on body rotation during pushing. Furthermore, it suggests that a proper combination of unilateral arm movement and foot placements could help to reduce body rotation even when pushing heavy objects. PMID:25498915

Lee, Yun-Ju; Aruin, Alexander S



Time Asymmetric Quantum Mechanics  

E-print Network

The meaning of time asymmetry in quantum physics is discussed. On the basis of a mathematical theorem, the Stone--von Neumann theorem, the solutions of the dynamical equations, the Schr\\"odinger equation (1) for states or the Heisenberg equation (6a) for observables are given by a unitary group. Dirac kets require the concept of a RHS (rigged Hilbert space) of Schwartz functions; for this kind of RHS a mathematical theorem also leads to time symmetric group evolution. Scattering theory suggests to distinguish mathematically between states (defined by a preparation apparatus) and observables (defined by a registration apparatus (detector)). If one requires that scattering resonances of width $\\Gamma$ and exponentially decaying states of lifetime $\\tau=\\frac{\\hbar}{\\Gamma}$ should be the same physical entities (for which there is sufficient evidence) one is led to a pair of RHS's of Hardy functions and connected with it, to a semigroup time evolution $t_{0}\\leq tbeginning of time, just like the big bang time for the universe, when it was a quantum system. The decay of quasi-stable particles is used to illustrate this quantum mechanical time asymmetry. From the analysis of these processes, we show that the properties of rigged Hilbert spaces of Hardy functions are suitable for a formulation of time asymmetry in quantum mechanics.

Arno R. Bohm; Manuel Gadella; Piotr Kielanowski



Generative pulsar timing analysis  

NASA Astrophysics Data System (ADS)

A new Bayesian method for the analysis of folded pulsar timing data is presented that allows for the simultaneous evaluation of evolution in the pulse profile in either frequency or time, along with the timing model and additional stochastic processes such as red spin noise, or dispersion measure variations. We model the pulse profiles using `shapelets' - a complete orthonormal set of basis functions that allow us to recreate any physical profile shape. Any evolution in the profiles can then be described as either an arbitrary number of independent profiles, or using some functional form. We perform simulations to compare this approach with established methods for pulsar timing analysis, and to demonstrate model selection between different evolutionary scenarios using the Bayesian evidence. The simplicity of our method allows for many possible extensions, such as including models for correlated noise in the pulse profile, or broadening of the pulse profiles due to scattering. As such, while it is a marked departure from standard pulsar timing analysis methods, it has clear applications for both new and current data sets, such as those from the European Pulsar Timing Array and International Pulsar Timing Array.

Lentati, L.; Alexander, P.; Hobson, M. P.



Asia Times Online  

NSDL National Science Digital Library

As the world's news flows increasingly from Asian nations, those people looking for a credible online source that concentrates on this region will find it in Asia Times Online. The site's front page features top stories from Asia Times journalists as well as from other online dailies and reports, including the South China Morning Post, Business Times Online, and the Australian Financial Review. The site offers separate sections for China, Southeast Asia, Japan, the Koreas, India/ Pakistan, Central Asia, and Oceania as well as departments devoted to Business Briefs, Global Economy, and Media and Industrial Technology. The entire site, including archives, is searchable.


Focus Issue: Time Passages  

NSDL National Science Digital Library

The development of life remains one of the most fascinating topics in modern biology. Our quest to discover unifying principles is rooted in a desire to find reason and order in processes that are at once overwhelming and chaotic. We have been vigorously engaged in dissecting development across species at molecular and genomic levels. The intricate machineries that have been uncovered so far operate together in precise manners, at not only the right places, but equally important, at the correct times. This week, Science's Special Issue on Developmental Timing describes our knowledge of some of the rules and measures of time, a core dimension in understanding how development is controlled.

Lisa D. Chong (American Association for the Advancement of Science; Associate Editor of Science's STKE and Associate Editor of Science REV)



Einstein and His Times  

NSDL National Science Digital Library

In this lesson, students will read about and research the major historical events that occurred throughout the year 1919. They will use different readings and articles to understand and describe what life was like during this time. In addition, the students will present their case as to whether or not Albert Einstein should be voted "Man of the Year" for 1919. This activity is from the Cosmic Times teachers guide and is intended to be used in conjunction with the 1919 Cosmic Times Poster.


Understanding Geological Time  

NSDL National Science Digital Library

In this classroom activity, middle school students gain an understanding of geologic time. The activity opens with background information for teachers about carbon and radiometric dating. In a classroom discussion, students share what they know about geologic time. Then, working in small groups responsible for different eras, students create a timeline for their assigned era by conducting library and Internet research. The activity concludes by having students review all the timelines to compare how long humans have been on the Earth to the length of time dinosaurs inhabited the planet.


Paradoxes of time travel  

E-print Network

Paradoxes that can supposedly occur if a time machine is created are discussed. It is shown that the existence of trajectories of ``multiplicity zero'' (i.e. trajectories that describe a ball hitting its younger self so that the latter cannot fall into the time machine) is not paradoxical by itself. This {\\em apparent paradox} can be resolved (at least sometimes) without any harm to local physics or to the time machine. Also a simple model is adduced for which the absence of {\\em true} paradoxes caused by self-interaction is proved.

S. Krasnikov



Effective Quantum Time Travel  

E-print Network

The quantum teleportation protocol can be used to probabilistically simulate a quantum circuit with backward-in-time connections. This allows us to analyze some conceptual problems of time travel in the context of physically realizable situations, to realize encrypted measurements of future states for which the decryption key becomes available only after the state is created, and to probabilistically realize a multistage quantum state processing within the time needed to complete only one stage. The probabilistic nature of the process resolves any paradox.

George Svetlichny



Position versus Time Graph  

NSDL National Science Digital Library

An animation of a red car moving to the right, hitting a wall and then moving backward to the left is shown. Also shown is one of four possible graphs depicting the car's position as a function of time.

Christian, Wolfgang; Belloni, Mario



Web Geologic Time Scale  

NSDL National Science Digital Library

The University of California-Berkeley Museum of Paleontology (last mentioned in the June 16, 1995 Scout Report) has recently updated its Web Geologic Time Scale, an online feature that helps users learn about the geologic timeline and explore related museum exhibits. The familiar geologic timeline appears on the main page of the Web site, with hypertext links for each division of time. Every page of the Web Geologic Time Machine site is liberally sprinkled with links to related UCMP Web pages; think of it as a portal to all online information available from the museum. Altogether, this Web site provides a well-organized and comprehensive resource for learning how the planet has changed over time, and would be a great addition to earth or life sciences classroom material for a broad range of grades.



GSA Geologic Time Scale  

NSDL National Science Digital Library

This Geological Society of America (GSA) site contains a detailed geologic time scale as an educational resource. It may be downloaded to a larger size, and includes all Eras, Eons, Periods, Epochs and ages as well as magnetic polarity information.



Comprehending Geologic Time  

NSDL National Science Digital Library

This online calculator helps students understand the classic analogy of relating the geologic time scale to a yard stick. It will help reinforce the concept of the briefness of human history relative to the age of the Earth.


Time Lapse Season Demonstrator  

NSDL National Science Digital Library

This animation demonstrates the changing declination of the sun with a time-lapse animation. It shows how the shadow of a building changes over the course of a year as the declination of the sun changes.

Lincoln, University O.


Time, energy & form  

E-print Network

Physical manifestations of time occur in natural forms of all sizes. Architectural form serves as shelter while providing a built envelope of human life, simultaneously influencing and influenced by energetic activities ...

McInnis, Martha Jane



Time to Go Local!  


... Bar Home Current Issue Past Issues Time to Go Local! Past Issues / Winter 2007 Table of Contents ... health topic pages, you will find "Go Local" links that take you to information about ...


Drug Retention Times  

SciTech Connect

The purpose of this monograph is to provide information on drug retention times in the human body. The information provided is based on plausible illegal drug use activities that might be engaged in by a recreational drug user.

Center for Human Reliability Studies



Drug Retention Times  

SciTech Connect

The purpose of this monograph is to provide information on drug retention times in the human body. The information provided is based on plausible illegal drug use activities that might be engaged in by a recreational drug user

Center for Human Reliability Studies



Global Temperature Time Series  

NSDL National Science Digital Library

The phenomenon is the rising and falling of temperatures on the Earth's surface. Click to choose a city on a regional map, showing graphs of the daily maximum, minimum, and mean temperatures for a 365 day time period.


The race against time.  


Two promising vaccines for Ebola virus disease are being tested in record time and - if all goes well - could be used to stop the outbreak ravaging parts of western Africa. Fiona Fleck and Ana Lesher report. PMID:25558101



Act in Time  

MedlinePLUS Videos and Cool Tools

DR. BRUCE MacLEOD: Heart disease is the number one killer of both women and men in this country. This ... seriously wrong with myself at the time. DR. BRUCE MacLEOD: Patients often tell me that they delayed ...


Time Matters Cynthia Selin  

E-print Network

School Technology Scenarios Systems Analysis Department Risø National Laboratory #12;KEY THEMES IN PHD of Nanotechnology ·Time & Nanotechnology ·Legitimization of Foresight ·Strategy #12;ON NANOTECHNOLOGY AS A FIELD 1


Timing control system  

NASA Technical Reports Server (NTRS)

A timing control system is disclosed which is particularly useful in connection with simulated mortar shells. Special circuitry is provided to assure that the shell does not overshoot, but rather detonates early in case of an improper condition; this ensures that ground personnel will not be harmed by a delayed detonation. The system responds to an externally applied frequency control code which is configured to avoid any confusion between different control modes. A premature detonation routine is entered in case an improper time-setting signal is entered, or if the shell is launched before completion of the time-setting sequence. Special provisions are also made for very early launch situations and improper detonator connections. An alternate abort mode is provided to discharge the internal power supply without a detonation in a manner that can be externally monitored, thereby providing a mechanism for non-destructive testing. The abort mode also accelerates the timing function for rapid testing.

Wiker, Gordon A. (Inventor); Wells, Jr., George H. (Inventor)



Timing Control System  

NASA Technical Reports Server (NTRS)

A timing control system is disclosed which is particularly useful in connection with simulated mortar shells. Special circuitry is provided to assure that the shell does not over shoot, but rather detonates early in case of an improper condition; this ensures that ground personnel will not be harmed by a delayed detonation. The system responds to an externally applied frequency control code which is configured to avoid any confusion between different control modes. A premature detonation routine is entered in case an improper time-setting signal is entered, or if the shell is launched before completion of the time-setting sequence. Special provisions are also made for very early launch situations and improper detonator connections. An alternate abort mode is provided to discharge the internal power supply without a detonation in a manner that can be externally monitored, thereby providing a mechanism for non-destructive testing. The abort mode also accelerates the timing function for rapid testing.

Wiker, Gordon A. (inventor); Wells, George H., Jr. (inventor)



Tsunami Travel Time Approximation  

NSDL National Science Digital Library

Eric Grosfils, Pomona College Summary Students are asked to calculate approximate tsunami travel times across the Pacific basin. The assignment builds off of a lab introducing students to Spatial Analyst, and ...

Grosfils, Eric


Gravitation with Two Times  

E-print Network

We investigate the possibility of constructing a covariant Newtonian gravitational theory and find that the action describing a massless relativistic particle in a background Newtonian gravitodynamic field has a higher-dimensional extension with two times.

W. Chagas-Filho



Media Time Family Pledge  


... or enable parent controls on their computers or gaming units. I will take the time to be ... Empowering Kids in the Digital World of Texting, Gaming, and Social Media (Copyright © 2011 American Academy of ...


Understanding Geologic Time  

NSDL National Science Digital Library

This informational tour offers students a basic understanding of geologic time, the evidence for events in the history of the Earth, relative and absolute dating techniques, and the significance of the Geologic Time Scale. Students move at a self-selected pace by answering questions correctly as they go. The teacher's guide contains all the details needed to use this computer activity, including handouts, a lesson plan, and assessment materials.

Scotchmoor, Judy


A Mesozoic time scale  

Microsoft Academic Search

We present an integrated geomagnetic polarity and stratigraphic time scale for the Triassic, Jurassic, and Cretaceous periods of the Mesozoic Era, with age estimates and uncertainty limits for stage boundaries. The time scale uses a suite of 324 radiometric dates, including high-resolution Ar-40\\/Ar-39 age estimates. This framework involves the observed ties between (1) radiometric dates, biozones, and stage boundaries, and

Felix M. Gradstein; Frits P. Agterberg; James G. Ogg; Jan Hardenbol; Paul van Veen; Jacques Thierry; Zehui Huang



Time Value of Money  

NSDL National Science Digital Library

This PowerPoint presentation from University of Tennessee's Suzan Murphy gives an excellent tutorial for the Time Value of Money, which is the concept that "money received sooner rather than later allows one to use the funds for investment or consumption purposes." The presentation focuses on methods of using a calculator (specifically Hewlett Packard 17B II calculator) to solve problems of Time Value. This easy-to-understand tutorial presents basic concepts, story problems, and solutions to the story problems.


Interactive Geological Time Scale  

NSDL National Science Digital Library

This time scale allows students to select multiple time periods from a list and view them on a highlighted display. It shows the relationship between eon, era, period, sub-period, and epoch and also includes the date in mega-annum (Ma) or millions of years before present. The scale reflects the changes in the Cenozoic Era (Tertiary and Quaternary have been eliminated and the Neogene modified) in the most recent International Stratigraphic Charts.


A Chinese Time Ontology  

Microsoft Academic Search

Temporal knowledge representation and identification are crucial in many application areas, such as Semantic Web, knowledge\\u000a sharing and reusing, and natural language processing. Building time ontologies has been viewed as a promising means to solve\\u000a this task. However, practical time ontology is closely related with specific nations and cultures, though they may share a\\u000a common part. In this paper, we

Chunxia Zhang; Cungen Cao; Yuefei Sui; Zhendong Niu



The Los Angeles Times  

NSDL National Science Digital Library

The Los Angeles Times debuts its Internet edition April 8. It is slated to include daily news and features, coverage of movies and entertainment, a computers and technology section, a special section devoted to Southern California sights and events, classified advertising, and chat boards. The site will be free. A fee based site will also be available, with access to Times' archives, as well as educational and research services.


American Time Use Survey

The American Time Use Survey (ATUS), conducted by the US Department of Labor, Bureau of Labor Statistics, is designed to collect information on how Americans spend their time on work, household chores, child care, recreation and other activities. The Applied Research Program (ARP) has provided funds to the US Department of Agriculture, Economic Research Service (USDA, ERS) to support the Eating and Health Module of the ATUS.


TechKnow Times  

NSDL National Science Digital Library

TechKnow Times(tm) specializes in selecting and synthesizing information about Internet resources. Its goal is to make information access as simple and as quick as possible. It covers news related to Internet and online marketing, World Wide Web sites and design, and online technology and culture, all drawn from a wide range of print and electronic sources. TechKnow Times(tm) is giving online entrepreneurs the information they need to accomplish their goals.



Time in quantum mechanics  

E-print Network

TIME IN QUANTUM MECHANICS A Thesis by KIMBERLY R. CHAPIN Submitted to Texas A8M University in partial fulfillment of the requirements for the degree of MASTER OF SCIENCE Approved as to style and content by: Marian O. Scully (Chair... of Committee) Edward S. Fry (Member) aan Laane (Member) Thomas W. Adair, III (Head of Department) August 1997 Major Subject: Physics TIME IN QIJANTUM MECHANICS A Thesis by KIMBERLY R. CHAPIN Submitted to the Oflice of Graduate Studies of Texas A...

Chapin, Kimberly R.



The thermodynamics of time  

E-print Network

The problem of time is a deep paradox in our physical description of the world. According to Aristotle's relational theory, time is a measure of change and does not exist on its own. In contrast, quantum mechanics, just like Newtonian mechanics, is equipped with a master clock that dictates the evolution of a system. This clock is infinitely precise and tacitly supplied free of charge from outside physics. Not only does this absolute time make it notoriously difficult to make a consistent theory of quantum gravity, it is also the underlying problem in establishing the second law. Indeed, contrary to our experience, the Wheeler-deWitt equation --a canonical quantization of general relativity-- predicts a static universe. Similarly, when simply concerned with the dynamics of a closed quantum system, there is no second law because the Von Neumann entropy is invariant under unitary transformations. Here we are mainly concerned with the latter problem and we show that it can be resolved by attributing a minimal amount of resources to the measurement of time. Although there is an absolute time in quantum mechanics, an observer can only establish a time by measuring a clock. For a local measurement, the minimal entropy production is equal to the number of ticks. This lower bound is attained by a black hole.

Dries Sels; Michiel Wouters



GABA Predicts Time Perception  

PubMed Central

Our perception of time constrains our experience of the world and exerts a pivotal influence over a myriad array of cognitive and motor functions. There is emerging evidence that the perceived duration of subsecond intervals is driven by sensory-specific neural activity in human and nonhuman animals, but the mechanisms underlying individual differences in time perception remain elusive. We tested the hypothesis that elevated visual cortex GABA impairs the coding of particular visual stimuli, resulting in a dampening of visual processing and concomitant positive time-order error (relative underestimation) in the perceived duration of subsecond visual intervals. Participants completed psychophysical tasks measuring visual interval discrimination and temporal reproduction and we measured in vivo resting state GABA in visual cortex using magnetic resonance spectroscopy. Time-order error selectively correlated with GABA concentrations in visual cortex, with elevated GABA associated with a rightward horizontal shift in psychometric functions, reflecting a positive time-order error (relative underestimation). These results demonstrate anatomical, neurochemical, and task specificity and suggest that visual cortex GABA contributes to individual differences in time perception. PMID:24647956

Russo, Sonia; Near, Jamie; Stagg, Charlotte J.; Cohen Kadosh, Roi



A Theory of Timed Automata  

Microsoft Academic Search

 We propose timed (finite) automata to model the behavior of realtime systems over time. Our definition provides a simple, and yet powerful, way to annotate state-transition graphs with timing constraints using finitely many realvalued clocks . A timed automaton accepts timed words --- infinite sequences in which a real-valued time of occurrence is associated with each symbol. We study timed

Rajeev Alur



Time-domain imaging  

NASA Technical Reports Server (NTRS)

The quest for the highest resolution microwave imaging and principle of time-domain imaging has been the primary motivation for recent developments in time-domain techniques. With the present technology, fast time varying signals can now be measured and recorded both in magnitude and in-phase. It has also enhanced our ability to extract relevant details concerning the scattering object. In the past, the interface of object geometry or shape for scattered signals has received substantial attention in radar technology. Various scattering theories were proposed to develop analytical solutions to this problem. Furthermore, the random inversion, frequency swept holography, and the synthetic radar imaging, have two things in common: (1) the physical optic far-field approximation, and (2) the utilization of channels as an extra physical dimension, were also advanced. Despite the inherent vectorial nature of electromagnetic waves, these scalar treatments have brought forth some promising results in practice with notable examples in subsurface and structure sounding. The development of time-domain techniques are studied through the theoretical aspects as well as experimental verification. The use of time-domain imaging for space robotic vision applications has been suggested.

Tolliver, C. L.



Constructing Time Machines  

E-print Network

The existence of time machines, understood as spacetime constructions exhibiting physically realised closed timelike curves (CTCs), would raise fundamental problems with causality and challenge our current understanding of classical and quantum theories of gravity. In this paper, we investigate three proposals for time machines which share some common features: cosmic strings in relative motion, where the conical spacetime appears to allow CTCs; colliding gravitational shock waves, which in Aichelburg-Sexl coordinates imply discontinuous geodesics; and the superluminal propagation of light in gravitational radiation metrics in a modified electrodynamics featuring violations of the strong equivalence principle. While we show that ultimately none of these constructions creates a working time machine, their study illustrates the subtle levels at which causal self-consistency imposes itself, and we consider what intuition can be drawn from these examples for future theories.

G. M. Shore



Agency, time, and causality  

PubMed Central

Cognitive Scientists interested in causal cognition increasingly search for evidence from non-Western Educational Industrial Rich Democratic people but find only very few cross-cultural studies that specifically target causal cognition. This article suggests how information about causality can be retrieved from ethnographic monographs, specifically from ethnographies that discuss agency and concepts of time. Many apparent cultural differences with regard to causal cognition dissolve when cultural extensions of agency and personhood to non-humans are taken into account. At the same time considerable variability remains when we include notions of time, linearity and sequence. The article focuses on ethnographic case studies from Africa but provides a more general perspective on the role of ethnography in research on the diversity and universality of causal cognition. PMID:25414683

Widlok, Thomas



Bleeding time at altitude.  

PubMed Central

Disorders of coagulation during ascent to high altitude in the unacclimatized are well recognized. In order to document the sequence of haematological changes, the bleeding time was estimated weekly in six climbers during a six week climb. The median bleeding time was shown to increase by 50% between the first and fourth week, it then plateaued during continued ascent to 5700 m. During the sixth week the bleeding time rapidly reverted to baseline levels whilst still at altitude. The observations might be explained by the compensatory changes in coagulation factors following the initial prothrombotic phase, compounded by increased capillary fragility. Acclimatization to altitude is accompanied by a series of complex haematological changes. The temporal sequence should be considered when devising a strategy to reduce the risk of thrombosis. PMID:7605410

Doughty, H A; Beardmore, C



Time in Quantum Gravity  

NASA Astrophysics Data System (ADS)

The Wheeler-DeWitt equation in quantum gravity is timeless in character. In order to discuss quantum to classical transition of the universe, one uses a time prescription in quantum gravity to obtain a time contained description starting from Wheeler-DeWitt equation and WKB ansatz for the WD wavefunction. The approach has some drawbacks. In this work, we obtain the time-contained Schrödinger-Wheeler-DeWitt equation without using the WD equation and the WKB ansatz for the wavefunction. We further show that a Gaussian ansatz for SWD wavefunction is consistent with the Hartle-Hawking or wormhole dominance proposal boundary condition. We thus find an answer to the small scale boundary conditions.

Biswas, S.; Shaw, A.; Modak, B.; Dolgov, A.


Reading Time Series Plots  

NSDL National Science Digital Library

This activity provides a brief introduction to GPS and provides a student activity to practice creating and reading time series plots with simplified GPS data. Students graph how a tectonic plate (and the GPS unit attached to it) has moved over a five year time period by moving a GPS model across a North-East coordinate graph. Students practice these skills by analyzing GPS time series from two GPS stations in Iceland. Teaching Tips Adaptations that allow this activity to be successful in an online environment Need to really transform to an online environment. I did have one participant draw the vectors on an online map of Iceland - however, only one person gets to do this, so I'd like to figure out other techniques for this. Elements of this activity that are most effective Recommendations for other faculty adapting this activity to their own course:

Olds, Shelley


Time and language.  


It is very interesting question whether time if a priori in mankind's thinking or whether it is a category which results from experience. Each human being has a memory so that he is able to distinguish between the past and the present, but not every language has a word expressing the common idea of time. In hunting and gathering populations such as Bushmen and Yumbri no one can state his own age. In chronobiology, the most important zeitgebers are the sun and the moon. Certain peasant peoples, such as the Santals and Mundas in India, even today use the same word to express sun, Sun-God, daylight, day, day-time, and hour. The first generalized idea of "time" seems to have arisen in the civilization of Old Mesopotamia. While the general meaning was still unknown to Sumerian, Accadian priest-astronomers presumably created the conception by generalization of the (Sumerian) foreign word itu(d) "mouth" and its mingling with the Accadian ittu(m) "sign (as an eclipse, monstrous birth, etc.), term, moment". We find the same root in the Etruscan itus "ides" from which it came as a loan-word into Latin (idus "ides"). Newton's term duratio can be found in earliest Iranian as yav- "yoke" and Vedic Indian as yugam "yoke" (i.e., a "bound" time). Some remarks are made concerning mankind's earliest chronobiological thinking where menstruation serves as a model. West African Kwa languages (predominantly Ewe), Old Indian, and early-classical chinese are evaluated. A brief survey is given of prehistoric peoples' migrations in terms of languages. The presentation concludes with an attempt to define time as an abstraction of abstractions, a fussy set (of ideas and definitions) in terms of post-classical set theory. PMID:7129063

Scharf, J H



Quantum time machine  

E-print Network

The continuation of Misner space into the Euclidean region is seen to imply the topological restriction that the period of the closed spatial direction becomes time-dependent. This restriction results in a modified Lorentzian Misner space in which the renormalized stress-energy tensor for quantized complex massless scalar fields becomes regular everywhere, even on the chronology horizon. A quantum-mechanically stable time machine with just the sub-microscopic size may then be constructed out of the modified Misner space, for which the semiclassical Hawking's chronology protection conjecture is no longer an obstruction.

Pedro F. Gonzalez-Diaz



Epistemology in Cyclic Time  

E-print Network

Consider the scenario, in which human civilization undergoes periodic eras of progression and regression, and consequently, changes in cosmological knowledge are cyclic. There exist solutions of general theory of relativity, such as the G\\"{o}del universe, in which the cosmos is rotating. If the real universe is indeed rotating, than this would be a reversion to rotating universe models, used in ancient cosmological models. We argue that such reversions in physical models would be inevitable in a space-time in which time is having $S^1$ (circular) topology.

Moninder Singh Modgil



The Geologic Time Scale  

NSDL National Science Digital Library

This site contains a large, easy to read, detailed geologic time scale for the Phanerozoic Eon (544 million years ago - Present). This is the period of time, also known as an eon, between the end of the Precambrian and today. The Phanerozoic begins with the start of the Cambrian period, 544 million years ago. It encompasses the period of abundant, complex life on Earth. The chart includes the Era, Period or System, and the Epoch or Series and features a brief description of each.


Sky Time: Kinesthetic Astronomy  

NSDL National Science Digital Library

Through a series of simple body movements, learners gain insight into the relationship between time and astronomical motions of Earth (rotation about its axis, and orbit around the Sun), and also about how these motions influence what we see in the sky at various times of the day and year. This activity can be used to introduce seasons on Earth and other planets. Learners will especially enjoy finding their birthdays in the orbit and using a zodiac diagram. This comprehensive lesson plan includes detailed background information, common misconceptions, extensions, teacher tips, references/resources, and FAQs.

Dr. Cherilynn A. Morrow



Times for interplanetary trips  

NASA Technical Reports Server (NTRS)

The times required to travel to the various planets at an acceleration of one g are calculated. Surrounding gravitational fields are neglected except for a relatively short distance near take-off or landing. The orbit consists of an essentially straight line with the thrust directed toward the destination up to the halfway point, but in the opposite direction for the remainder so that the velocity is zero on arrival. A table lists the approximate times required, and also the maximum velocities acquired in light units v/c for the various planets.

Jones, R. T.



New York Times: Circuits  

NSDL National Science Digital Library

Circuits is a new New York Times weekly offering intended to enhance the newspaper's technology coverage. It contains regular gaming and computer columns, along with an eclectic mix of articles and essays that address in a general way the interaction between humans and technology. The first three issues contained articles on where computers go to die, music and jobs on the web, computer games for girls, online auctions, home theatre, web TV, and computer ergonomics, among others. At present, Circuit archives are available. Note that the New York Times is freely available (after required registration) to users in the US.



Translating Real-Time UML Timing Constraints into Real-Time Logic Formulas  

E-print Network

and the Institute for Space Systems Operations. #12;1 Translating Real-Time UML Timing Constraints into Real-Time and Albert Mo Kim Cheng Real-Time Systems Laboratory Department of Computer Science University of Houston Modeling, Real-Time Systems, Timing Constraints, Verification, RTL Abstract Real-time software development

Cheng, Albert M. K.


Time in Cosmology  

E-print Network

The notion of time in cosmology is revealed through an examination of transition matrix elements of radiative processes occurring in the cosmos. To begin with, the very concept of time is delineated in classical physics in terms of correlations between the succession of configurations which describe a process and a standard trajectory called the clock. The total is an isolated system of fixed energy. This is relevant for cosmology in that the universe is an isolated system which we take to be homogeneous and isotropic. Furthermore, in virtue of the constraint which arises from reparametrization invariance of time, it has total energy zero. Therefore the momentum of the scale factor is determined from the energy of matter. In the quantum theory this is exploited through use of the WKB approximation for the wave function of the scale factor, justified for a large universe. The formalism then gives rise to matrix elements describing matter processes. These are shown to take on the form of usual time dependent quantum amplitudes wherein the temporal dependence is given by a background which is once more fixed by the total energy of matter.

R. Brout; R. Parentani



The virtual time machine  

Microsoft Academic Search

A parallel computer architecture is proposed that is based on an optimistic style of execution. Specifically, the Virtual Time Machine (VTM) detects violations of data depen- dence constraints at runtime, and automatically recovers from them. In order to efficiently implement this mecha- nism, a sophisticated, two-dimensional memory system is proposed that is addressed using both a spatial and a tern.

Richard M. Fujimoto



Infinite Time Turing Machines  

Microsoft Academic Search

We extend in a natural way the operation of Turing machines to infinite ordinal time, and investigate the resulting supertask theory of computability and decidability on the reals. Every ?11 set, for example, is decidable by such machines, and the semi-decidable sets form a portion of the ?12 sets. Our oracle concept leads to a notion of relative computability for

Joel David Hamkins; Andy Lewis



The First Time  

ERIC Educational Resources Information Center

In this article, the author narrates her experience of meeting a Montessori kid for the first time and shares the characteristics she observed in Montessori students. The author was working as director of academic resources in university housing at the University of Wisconsin-Madison and met Jason, a pre-med sophomore who was the resident…

Black, Beth



TIMED Spacecraft Mobile  

NSDL National Science Digital Library

This is a mobile for students to assemble, aimed at enhancing their knowledge of NASA spacecraft and scientific facts Each element of the mobile contains an image and one fact or scientific concept. The cover contains background information about NASA-s TIMED mission, and two language arts exercises to reinforce space science vocabulary.



Where in Time?  

ERIC Educational Resources Information Center

In this article, the authors describe an activity developed to assist students with constructing their own understanding of Earth's history and provide questions to help teach the geologic time scale. The lesson is aligned to the following National Science Education Standards: Science as Inquiry, Earth's History, and Nature of Science. While…

Pecore, John; Sacks, David



Geologic time scale bookmark  

USGS Publications Warehouse

This bookmark, designed for use with U.S. Geological Survey activities at the 2nd USA Science and Engineering Festival (April 26–29, 2012), is adapted from the more detailed Fact Sheet 2010–3059 "Divisions of Geologic Time." The information that it presents is widely sought by educators and students.

U.S. Geological Survey



Fuzzy Space-Time  

E-print Network

A review is made of recent efforts to define linear connections and their corresponding curvature within the context of noncommutative geometry. As an application it is suggested that it is possible to identify the gravitational field as a phenomenological manifestation of space-time commutation relations and to thereby clarify its role as an ultraviolet regularizer.

J. Madore



Time-Encoded Imagers.  

SciTech Connect

This report provides a short overview of the DNN R&D funded project, Time-Encoded Imagers. The project began in FY11 and concluded in FY14. The Project Description below provides the overall motivation and objectives for the project as well as a summary of programmatic direction. It is followed by a short description of each task and the resulting deliverables.

Marleau, Peter; Brubaker, Erik



Temperature Compensated Time Synchronization  

Microsoft Academic Search

Time synchronization in embedded sensor networks is an important service for correlating data between nodes and communication scheduling. While many different approaches to the problem are possible, one major effect of clock frequency difference between nodes, environmental temperature changes, has often been left out of the solution. The common assumption that the temperature is static over a certain period of

Thomas Schmid; Zainul Charbiwala; Roy Shea; Mani B. Srivastava



Temperature Driven Time Synchronization  

Microsoft Academic Search

Time synchronization in embedded sensor networks is an important service for correlating data between nodes and communication scheduling. While many different approaches to the problem are possible, one major effect of clock frequency difference between nodes, environ- mental temperature changes, has often been left out of the solution. The common assumption that the temperature is static over a certain period

Thomas Schmid; Zainul Charbiwala; Mani B. Srivastava


Time, history and revolution  

Microsoft Academic Search

To paraphrase the Ninth Thesis on Feuerbach, one could say that, as opposed to speculative materialism, dialectical materialism conceives the time of social development as a practical activity, and not as a factor that can be taken in isolation, a neutral parameter of development. Regis Debray [1

Ulysses Santamaria; J. Anglin; MARXIST TRADITION



Paleogeography Through Geologic Time  

NSDL National Science Digital Library

This website contains paleogeographic and plate tectonic reconstructions organized by geologic period. Users select a geologic period, and receive a summary of the major events that occurred during that period, a paleogeographic map, tectonics and sedimentation of the North Atlantic region, and global tectonic features from that time.

Blakey, Ronald


Decay Time of Cathodoluminescence  

ERIC Educational Resources Information Center

Simple measurements of the decay time of cathodoluminescence are described. Cathodoluminescence is used in many devices, including computer monitors, oscilloscopes, radar displays and television tubes. The experimental setup is simple and easy to build. Two oscilloscopes, a function generator, and a fast photodiode are needed for the experiments.…

Kraftmakher, Yaakov



Time for Renewal  

ERIC Educational Resources Information Center

During hard economic times, college health professionals must urge their supervisors and administrators to help them maintain or find new funding so that they can attend regional and national conferences of the American College Health Association. In this viewpoint, a nurse from a small college shares the various sources of funding she discovered…

Nielsen, Patricia D.



Correlating Aluminum Burning Times  

Microsoft Academic Search

Characteristics of aluminum combustion are summarized in an overview of the subject, focusing on the burning time of individual particles. Combustion data from over ten different sources with almost 400 datum points have been cataloged and correlated. Available models have also been used to evaluate combustion trends with key environmental parameters. The fundamental concepts that control aluminum combustion are discussed,

M. W. Beckstead



Reaction Time Sound Explanation  

NSDL National Science Digital Library

This experiment presents auditory stimuli and requires the participant to respond after hearing target stimuli under different conditions. This experiment gives students the opportunity to determine whether their reaction times are reliably different for tasks that require slightly different decisions. This page provides guidance for faculty who wish to incorporate this activity into their classroom.


Making Time for Caring.  

ERIC Educational Resources Information Center

Describes the adoption of advisory time at the middle level as an opportunity to implement effective communication activities in place of cognitive activities and the structured curriculum. Argues that students learn important listening, communication, and respecting skills when proper tools are introduced and utilized, and when the program has…

O'Neil, Marian



Leadership in Challenging Times  

ERIC Educational Resources Information Center

In spite of tough financial times, resourceful school leaders devise ways to overcome challenges and improve education. To do this, they make strategic use of the resources they have. And they also cultivate learning communities. In this article, Elizabeth A. City describes how school leaders can make more strategic use of three essential…

City, Elizabeth A.



Optoelectronic time division multiplexing  

NASA Astrophysics Data System (ADS)

The concept of using optoelectronic (photoconductive) switches as the sampling element in time division multiplexing is introduced in the context of VLSI off-chip data transmission. A 4:1 multiplexer was fabricated in Cr:GaAs, activated by a GaAs laser via optical fibre delay lines and operated at 2.5 Gbit/s.

Albares, D. J.; Garcia, G. A.; Chang, C. T.; Reedy, R. E.



Time reversal communication system  


A system of transmitting a signal through a channel medium comprises digitizing the signal, time-reversing the digitized signal, and transmitting the signal through the channel medium. The channel medium may be air, earth, water, tissue, metal, and/or non-metal.

Candy, James V. (Danville, CA); Meyer, Alan W. (Danville, CA)



Saving Time with Technology  

ERIC Educational Resources Information Center

In order to help teachers envision digital products in action in classrooms, the authors look at three examples of how teachers they know enhance learning time by employing technology efficiently. The examples include: (1) a social studies teacher who begins each class period with a three-question formative assessment using the website…

Gullen, Kristine; Zimmerman, Holly



Time for the Sundial.  

ERIC Educational Resources Information Center

Discusses the accuracy of sundials and many factors which affect their ability to measure apparent local time. Provides directions for constructing a sundial, including how to make a universal dial. Includes background information regarding other types of sundials and descriptions of notable sundials. (DDR)

Andrews, Tony



The time travel paradox  

E-print Network

We define the time travel paradox in physical terms and prove its existence by constructing an explicit example. We argue further that in theories -- such as general relativity -- where the spacetime geometry is subject to nothing but differential equations and initial data no paradoxes arise.

S. Krasnikov



TIME MANAGEMENT Other Handouts  

E-print Network

and other weeks where everything seems due. Step 3: Backward Planning Backward planning is useful and working towards your goals. Step 1: Gather your Tools Gather the tools you will need to plan your time (lectures /workshops/tutorials/laboratories) Step 2: Identify Priorities Go through each of your unit guides


Time and Moral Judgment  

ERIC Educational Resources Information Center

Do moral judgments hinge on the time available to render them? According to a recent dual-process model of moral judgment, moral dilemmas that engage emotional processes are likely to result in fast deontological gut reactions. In contrast, consequentialist responses that tot up lives saved and lost in response to such dilemmas would require…

Suter, Renata S.; Hertwig, Ralph



Time as the Integrative Factor.  

ERIC Educational Resources Information Center

How adults change over time is best understood through consideration of three kinds of time: historical time period, chronological age, and culturally specific social timetable of life events. Time provides a context for understanding developmental processes. (SK)

Merriam, Sharan B.



The Theory of Timed Automata  

Microsoft Academic Search

We propose timed automata to model the behavior of real-time systems over time. Our definition provides a simple, and yet powerful, way to annotate state-transition graphs with timing constraints using finitely many real-valued clocks. A timed automaton accepts timed words — strings in which a real-valued time of occurrence is associated with each symbol. We study timed automata from the

Rajeev Alur



Time Varying Feature Data  

NASA Astrophysics Data System (ADS)

The infrastructure to gather, store and access information about our environment is improving and growing rapidly. The increasing amount of information allows us to get a better understanding of the current state of our environment, historical processes and to simulate and predict the future state of the environment. Finer grained spatial and temporal data and more reliable communications make it easier to model dynamic states and ephemeral features. The exchange of information within and across geospatial domains is facilitated through the use of harmonized information models. The Observations & Measurements (O&M) developed through OGC and standardised by ISO is an example of such a cross-domain information model. It is used in many domains, including meteorology, hydrology as well as the emergency management. O&M enables harmonized representation of common metadata that belong to the act of determining the state of a feature property, whether by sensors, simulations or humans. In addition to the resulting feature property value, information such as the result quality but especially the time that the result applies to the feature property can be represented. Temporal metadata is critical to modelling past and future states of a feature. The features, and the semantics of each property, are defined in domain specific Application Schema using the General Feature Model (GFM) from ISO 19109 and usually encoded following ISO 19136. However, at the moment these standards provide only limited support for the representation and handling of time varying feature data. Features like rivers, wildfires or gas plumes have a defined state - for example geographic extent - at any given point in time. To keep track of changes, a more complex model for example using time-series coverages is required. Furthermore, the representation and management of feature property value changes via the service interfaces defined by OGC and ISO - namely: WFS and WCS - would be rather complex. Keeping track of feature property value corrections or even feature (state change) cancellations for auditing purposes is also not easy to achieve. The aviation domain has strong requirements to represent and manage the state of aeronautical features through time. Being able to efficiently encode and manage feature state changes, keeping track of all changes for auditing purposes and being able to determine the future state of an aeronautical feature as currently known to the system are vital for aeronautical applications. In order to support these requirements, the Aeronautical Information Exchange Model (AIXM) which has been developed by the aviation domain is based on the so called AIXM Temporality Model (AIXM-TM). The AIXM-TM defines various rules for modeling, representing and handling the state of aeronautical features through time. This is a promising approach that can be incorporated into the GFM so that ultimately the modeling and management of time varying feature data is supported in an interoperable and harmonized way in all geospatial domains. This presentation gives an introduction to the main concepts of the AIXM-TM. It also shows how the GFM can be extended to support time varying feature data. Finally, the relationship of O&M and time varying features is discussed.

Echterhoff, J.; Simonis, I.; Atkinson, R.



Time Dependent Volcano Deformation  

NASA Astrophysics Data System (ADS)

Time varying deformation can arise due to changes in magma pressure, evolution of the source geometry (e.g., dike propagation), or time dependent response of the surrounding crust. It is important to understand the signatures of these processes in order to distinguish between them. Here I explore time dependent surface deformation due to viscoelastic and poroelastic relaxation of the crust surrounding simplified magma chambers. Viscoelastic deformation is considered in a shell surrounding a spherical magma chamber in a half-space (as analyzed numerically by Newman et al, 2001). The full space solution for a Maxwell rheology was given by Dragoni and Magnanensi (PEPI, 1989). An approximate half-space solution is simply constructed following the approach of McTigue (JGR, 1987) as long as the outer radius R2 is small compared to the depth d. The surface displacements are scaled, time-dependent versions of the Mogi solution in an elastic half-space. For a step increase in magma pressure (other source histories are also simply constructed) uz (?, z=0, t) = (1 - ?) p0 R13 / ? d2 [ e-t/tR + R23 / R13 ( 1 - e-t/tR ) ] 1 / (1 + ?2)3/2 where R1 is the magma chamber radius, ? is the normalized radial distance from the center of the source, and the characteristic relaxation time is tR = (3?/?)(1-?)/(1+?)(R2/R1)3, where ? is viscosity and ? is shear modulus. The post-intrusion displacements scale with (R2/R1)3 - 1 and can be significant. For example, a viscoelastic shell of only 20% the radius of the magma chamber leads to time dependent displacements that are 70% of the instantaneous elastic displacements. An approximate fully time-dependent solution for a cylindrical (plane strain) magma chamber in a homogeneous poro-elastic half-space is constructed as the superposition of the solution due to an expanding chamber in a full plane, and distributed shear and normal loads on a poroelastic half-space. The full-space solution is pure shear and thus induces no change in pore pressure. Consequently, the distributed loads necessary to cancel the imposed tractions on the free surface are time invariant. The surface displacements due to the applied surface loads are found using displacement potentials in the Fourier-Laplace domain; the Laplace transforms are inverted analytically. The vertical velocity resulting from the instantaneous inflation of the magma chamber is 2 ? vz(z=0,t) = ? (1-?) [ N? - i sgn(k) T? ] ? c/? t e- c k2 t - c k ?1-? e-? c k2 terfc( ?c (1-?) k2 t) where k is horizontal wavenumber, c is hydraulic diffusivity, ?{1-?} = 1-2?2, ?2 = ?u - ?/1-? , ?u is the undrained Poisson's ratio, and N? and T? are the Fourier transformed normal N and shear T tractions acting on the plane z = 0, N = (? ? V/? ) (x2- d2) /(d2 + x2)2, T = (2? ? V/ ? )dx/(d2 + x2)2. The displacement immediately above the source increases monotonically, however the flanking regions subside for some time following the initial elastic uplift before further uplifting. This arises because pore fluid flows from the flanking region to the center of uplift. The final uplift is identical to the initial elastic uplift but increased by a factor of ?u-?.

Segall, P.



Are animals stuck in time?  

Microsoft Academic Search

People can time travel cognitively because they can remember events having occurred at particular times in the past (episodic memory) and because they can anticipate new events occurring at particular times in the future. The ability to assign points in time to events arises from human development of a sense of time and its accompanying time-keeping technology. The hypothesis is

William A. Roberts



Principles of Discrete Time Mechanics  

NASA Astrophysics Data System (ADS)

1. Introduction; 2. The physics of discreteness; 3. The road to calculus; 4. Temporal discretization; 5. Discrete time dynamics architecture; 6. Some models; 7. Classical cellular automata; 8. The action sum; 9. Worked examples; 10. Lee's approach to discrete time mechanics; 11. Elliptic billiards; 12. The construction of system functions; 13. The classical discrete time oscillator; 14. Type 2 temporal discretization; 15. Intermission; 16. Discrete time quantum mechanics; 17. The quantized discrete time oscillator; 18. Path integrals; 19. Quantum encoding; 20. Discrete time classical field equations; 21. The discrete time Schrodinger equation; 22. The discrete time Klein-Gordon equation; 23. The discrete time Dirac equation; 24. Discrete time Maxwell's equations; 25. The discrete time Skyrme model; 26. Discrete time quantum field theory; 27. Interacting discrete time scalar fields; 28. Space, time and gravitation; 29. Causality and observation; 30. Concluding remarks; Appendix A. Coherent states; Appendix B. The time-dependent oscillator; Appendix C. Quaternions; Appendix D. Quantum registers; References; Index.

Jaroszkiewicz, George



Learning precisely timed spikes.  


To signal the onset of salient sensory features or execute well-timed motor sequences, neuronal circuits must transform streams of incoming spike trains into precisely timed firing. To address the efficiency and fidelity with which neurons can perform such computations, we developed a theory to characterize the capacity of feedforward networks to generate desired spike sequences. We find the maximum number of desired output spikes a neuron can implement to be 0.1-0.3 per synapse. We further present a biologically plausible learning rule that allows feedforward and recurrent networks to learn multiple mappings between inputs and desired spike sequences. We apply this framework to reconstruct synaptic weights from spiking activity and study the precision with which the temporal structure of ongoing behavior can be inferred from the spiking of premotor neurons. This work provides a powerful approach for characterizing the computational and learning capacities of single neurons and neuronal circuits. PMID:24768299

Memmesheimer, Raoul-Martin; Rubin, Ran; Olveczky, Bence P; Sompolinsky, Haim



Timing is Everything  

SciTech Connect

You want to be ahead of the curve, but not so far ahead that no one can see you. Historically, the scientific community has tended to ignore science that is too innovative or ahead of its time. For this, we are often accused of being biased towards maintaining some fictional status quo. The reason these papers often get forgotten, however, has more to do with the usability of innovative ideas, rather than some perverseness. The classic case is Mendel, whose pioneering ideas on inheritance were ignored for many years. It wasn’t because the scientific community did not know about him; Mendel simply addressed different questions than other scientists at the time. Years later, when chromosomes were identified as a potential mechanism for transmitting genetic information, his ideas suddenly became relevant to a much wider scientific audience.

Wiley, H. S.



Sensorimotor Function, Gait Patterns and Falls in Community-dwelling Women  

Microsoft Academic Search

Summary Tests of vision, vestibular function, peripheral sensation, strength, reaction time, balance and gait were administered to 183 community-dwelling women aged 22-99 years. Walking speed, stride length and cadence declined with age with corresponding increases in stance duration and percentage of the stride in the stance phase. Visual acuity and contrast sensitivity, tactile and vibration sense in the lower limb,




Telescopes as Time Machines  

NSDL National Science Digital Library

This fun, nighttime hands-on astronomy activity lets learners explore how long it takes for light from different objects in the universe to reach Earth. The activity shows participants the difference among three distance categories: within our Solar System, within the Milky Way, and within the rest of the universe. The PDF contains step-by-step instructions, photos, presentation tips, ready-to-print "Passport through Time" activity handout, and links to background information.

Pacific, Astronomical S.



Space Time Foam  

Microsoft Academic Search

In the context of a model of space-time foam, made by N wormholes we discuss the possibility of having a foam formed by different configurations. An equivalence between Schwarzschild and Schwarzschild-Anti-de Sitter wormholes in terms of Casimir energy is shown. An argument to discriminate which configuration could represent a foamy vacuum coming from Schwarzschild black hole transition frequencies is used.

Remo Garattini; Viale Marconi



The Best of Times  

NSDL National Science Digital Library

This interactive Flash book of poems by Greg Tang and pictures by Harry Briggs helps children master their times tables through a deeper, more intuitive understanding of multiplication instead of memorization. Students use partial products to multiply larger numbers, first breaking them into smaller, more manageable parts. After reading the poem and examples, learners can test themselves by applying the strategies to a series of 3-5 challenges.

Greg Tang



TIMED Spacecraft Model  

NSDL National Science Digital Library

This is a model for students to assemble, aimed at enhancing their knowledge of NASA spacecraft and scientific facts. The cover of this four-color tri-fold contains background information about the Thermosphere, Ionosphere, Mesosphere Energetics and Dynamics (TIMED) mission as well as two language arts activities to reinforce space science vocabulary and concepts. This product is available in hardcopy and electronic formats.



A Journey Through Time  

NSDL National Science Digital Library

This activity has students create a travel brochure of a geologic period. Links are provided to research questions about the dominant life forms, position of the continents, and climate of the period. Questions in the conclusion section are for students to consider the duration of human existence compared to geologic time, why dinosaurs and humans never fought, and whether they would want to travel to their chosen geologic period.

Schneider, Amy



NSDL National Science Digital Library

WhaleTimes will take young users on an adventure to the ocean. This resource provides a wealth of information and pictures on popular sea life, such as whales, seals, sea lions, sharks, penguins, and walruses. It helps the user to find out how animals survive in the sea, what they eat, where they live and much more. There are several computer activities for young kids, and a list of books that focus on sea life and are appropriate for young audiences.


The Timing of Sonoluminescence  

E-print Network

We measured the timing of sonoluminescence by observing laser light scattered from a single sonoluminescing bubble. We performed this measurement on 23.5 kHz, 17.8 kHz, 13.28 kHz and 7920 Hz systems, and found that the flash typically occurs 100 nanoseconds before the minimum radius. These results motivate a new model of sonoluminescence: the flash results from the discharge of an excited cold condensate formed during the adiabatic expansion of the bubble.

Thomas E. Brennan; Gustave C. Fralick



Reaction Time 2: Zap!  

NSDL National Science Digital Library

This Science NetLinks lesson is the second of a two-part series that encourages students to think about their own learning and the strategies that best help them learn new skills and ideas. In this lesson, students build upon what they have already learned by participating in another online reaction-time activity--this one testing their visual and auditory abilities, both separately and together.

Science Netlinks;



Einstein in Time  

NSDL National Science Digital Library

This fun Web site is part of OLogy, where kids can collect virtual trading cards and create projects with them. Here, they are introduced to Einstein's scientific and humanitarian pursuits with two engaging, kid-friendly sections: Einstein in Time, a fascinating look at the major events in his life presented in a timeline and Everyday Einstein: Humanitarian, a quick overview of how he used his fame to draw attention to the things he believed in.


Segmental colonic transit time  

Microsoft Academic Search

Mean segmental transit time of radiopaque markers through the right colon, left colon and rectosigmoid areas of adults and\\u000a children has been calculated from their distribution on consecutive plain films of the abdomen. Overall mean transit does\\u000a not differ significantly in the large bowel between adults and children. However, there are regional differences within the\\u000a colon in relation to age.

Pierre Arhan; Ghislain Devroede; Bertrand Jehannin; Michel Lanza; Claude Faverdin; Catherine Dornic; Bernard Persoz; Léon Tétreault; Bernard Perey; Denys Pellerin



Music in Galileo's Time  

NASA Astrophysics Data System (ADS)

Claudio Monteverdi appears as the key personality of the music in Galileo's time. His revolution in format and function of the musical language-from an essentially edonistic creation of purely sonorous images to a musical language consciously "expressive" of the content of the words on which it is based-is similar in character to the influential innovations in scientific thinking operated by Galileo.

Petrobelli, P.



Bath Time with Archimedes  

NSDL National Science Digital Library

This algebra lesson helps students make the connection between functions and their graphs. The model of the level of water in a bathtub is used. Students will watch the graph and a chart of the depth of the water at different time increments. They are then asked to identify the events that caused each change in the graph. A student worksheet is available for download here in a Word Document.



Optimal time discrimination.  


In the temporal bisection task, participants categorize experienced stimulus durations as short or long based on their similarity to previously acquired reference durations. Reward maximization in this task requires integrating endogenous timing uncertainty as well as exogenous probabilities of the reference durations into temporal judgements. We tested human participants on the temporal bisection task with different short and long reference duration probabilities (exogenous probability) in two separate test sessions. Incorrect categorizations were not penalized in Experiment 1 but were penalized in Experiment 2, leading to different levels of stringency in the reward functions that participants tried to maximize. We evaluated the judgements within the framework of optimality. Our participants adapted their choice behaviour in a nearly optimal fashion and earned nearly the maximum possible expected gain they could attain given their level of endogenous timing uncertainty and exogenous probabilities in both experiments. These results point to the optimality of human temporal risk assessment in the temporal bisection task. The long categorization response times (RTs) were overall faster than short categorization RTs, and short but not long categorization RTs were modulated by reference duration probability manipulations. These observations suggested an asymmetry between short and long categorizations in the temporal bisection task. PMID:25026179

Co?kun, Filiz; Sayal?, Zeynep Ceyda; Gürbüz, Emine; Balc?, Fuat



The thermodynamics of time  

E-print Network

The problem of time is a deep paradox in our physical description of the world. According to Aristotle's relational theory, time is a measure of change and does not exist on its own. In contrast, quantum mechanics, just like Newtonian mechanics, is equipped with a master clock that dictates the evolution of a system. This clock is infinitely precise and tacitly supplied free of charge from outside physics. Not only does this absolute time make it notoriously difficult to make a consistent theory of quantum gravity, it is also the underlying problem in establishing the second law. Indeed, contrary to our experience, the Wheeler-deWitt equation --a canonical quantization of general relativity-- predicts a static universe. Similarly, when simply concerned with the dynamics of a closed quantum system, there is no second law because the Von Neumann entropy is invariant under unitary transformations. Here we are mainly concerned with the latter problem and we show that it can be resolved by attributing a minimal am...

Sels, Dries



The sun in time  

NASA Technical Reports Server (NTRS)

Various papers on solar science are presented. The optics considered include: variability of solar irradiance, sunspot number, solar diameter, and solar wind properties; theory of luminosity and radius variations; standard solar models; the sun and the IMF; variations of cosmic-ray flux with time; accelerated particles in solar flares; solar cosmic ray fluxes during the last 10 million yrs; solar neutrinos and solar history; time variations of Be-10 and solar activity; solar and terrestrial components of the atmospheric C-14 variation spectrum; solar flare heavy-ion tracks in extraterrestrial objects. Also addressed are: the faint young sun problem; atmospheric responses to solar irradiation; quaternary glaciations; solar-terrestrial relationships in recent sea sediments; magnetic history of the sun; pre- and main-sequence evolution of solar activity; magnetic activity in pre-main-sequence stars; classical T Tauri stars; relict magnetism of meteorites; luminosity variability of solar-type stars; evolution of angular momentum in solar-mass stars; time evolution of magnetic fields on solarlike stars.

Sonett, Charles P. (editor); Giampapa, Mark S. (editor); Matthews, Mildred S. (editor)



The sun in time  

NASA Astrophysics Data System (ADS)

Various papers on solar science are presented. The optics considered include: variability of solar irradiance, sunspot number, solar diameter, and solar wind properties; theory of luminosity and radius variations; standard solar models; the sun and the IMF; variations of cosmic-ray flux with time; accelerated particles in solar flares; solar cosmic ray fluxes during the last 10 million yrs; solar neutrinos and solar history; time variations of Be-10 and solar activity; solar and terrestrial components of the atmospheric C-14 variation spectrum; solar flare heavy-ion tracks in extraterrestrial objects. Also addressed are: the faint young sun problem; atmospheric responses to solar irradiation; quaternary glaciations; solar-terrestrial relationships in recent sea sediments; magnetic history of the sun; pre- and main-sequence evolution of solar activity; magnetic activity in pre-main-sequence stars; classical T Tauri stars; relict magnetism of meteorites; luminosity variability of solar-type stars; evolution of angular momentum in solar-mass stars; time evolution of magnetic fields on solarlike stars.

Sonett, Charles P.; Giampapa, Mark S.; Matthews, Mildred S.


Commission 31: Time  

NASA Astrophysics Data System (ADS)

The most intensely discussed and controversial issue in time keeping has been the proposal before the International Telecommunications Union (ITU) to redefine Coordinated Universal Time (UTC) so as to replace leap seconds by leap hours. Should this proposal be adopted, the practice of inserting leap seconds would cease after a specific date. Should the Earth's rotation continue to de-accelerate at its historical rate, the next discontinuity in UTC would be an hour inserted several centuries from now. Advocates of this proposal cite the need to synchronize satellite and other systems, such as GPS, Galileo, and GLONASS, which did not exist and were not envisioned when the current system was adopted. They note that leap second insertions can be and have been incorrectly implemented or accounted for. Such errors have to date had localized impact, but they could cause serious mishaps involving loss of life. For example, some GPS receivers have been known to fail simply because there was no leap second after a long enough interval, other GPS receivers failed because the leap second information was broadcast more than three months in advance, and some commercial software used for internet time-transfer Network Time Protocol (NTP) could either discard all data received after a leap second or interpret it as a frequency change. The ambiguity associated with the extra second could also disrupt financial accounting and certain forms of encryption. Those opposed to the proposal question the need for a change, and also point out the costs of adjusting to the proposed change and its inconvenience to amateur astronomers and others who rely upon astronomical calculations published in advance. Reports have been circulated that the cost of checking and correcting software to accommodate the new definition of UTC would be many millions of dollars for some systems. In October 2005 American Astronomical Society asked the ITU for a year's time to study the issue. This commission has supported the efforts of the IAU' s Committee on the Leap Second to make an informed recommendation, and anticipates considerable discussion at the IAU's 26th General Assembly in 2006.

Matsakis, Demetrios; Defraigne, Pascale; Hosokawa, M.; Leschiutta, S.; Petit, G.; Zhai, Z.-C.



Minimizing Busy Time in Multiple Machine Real-time Scheduling  

E-print Network

Minimizing Busy Time in Multiple Machine Real-time Scheduling Rohit Khandekar1 , Baruch Schieber1 with a release time, a due date, a processing time and demand for machine capacity. The goal is to schedule all of the jobs non-preemptively in their release-time-deadline windows, subject to machine capacity constraints

Shachnai, Hadas



E-print Network

Indoor Cycling 1110 6:30-7:30pm Judo 2040 7:00-9:00pm WEDNESDAYWEDNESDAY Class Room Time Bootcamp 2015 12:00-1:00pm CoreX 2025 5:15-5:45pm Yoga 2015 5:15-6:15pm Bootcamp 2015 6:30-7:30pm Judo 2040 7:00-9:00pm 12:15-12:45pm Bootcamp 2015 5:15-6:15pm Judo 2040 7:00-9:00pm No Classes:No Classes: Monday, May 26

Hemmers, Oliver


Time-Varying Quantiles  

E-print Network

¤erence between Q (:05) and the median, Q (:5), may be slowly changing, or even time invariant, even though the individual quantiles are changing rapidly. How do the q0s vary with #28;? The Monte Carlo experiments reported below are designed to throw some light... size, results in an estimator that is very close to these infeasible estimators. Table 2 illustrates a Monte Carlo experiment with the same design as in table 1 except that the sample size increased from 100 to 500. It is reas- suring that the median...

Harvey, Andrew C; De Rossi, Giuliano


New York Times: Business  

NSDL National Science Digital Library

The New York Times has redesigned the business section on its web site; it features the latest business news and updates from the stock market. A Business Briefcase section has now been added; this section features the latest business books, business travel, the mutual funds quarterly report, company capsules from Hoover's Inc., and the latest loan and deposit rates from BanxQuote. The Your Money section caters to the personal investor; it provides investors with articles on investing, tools for managing their portfolio and a forum for discussing the stock market. Users in the United States may access the site free of charge after registering.


TIMED Doppler Interferometer  

NASA Technical Reports Server (NTRS)

The Timed Doppler Interferometer (TIDI) will accurately and precisely determine the global vector MLTI (Mesosphere and Lower Thermosphere) wind, temperature, and density profiles. It will measure characteristics of the gravity wave and planetary wave spectra. The tidal characteristics of temperature, density, and wind in the MLTI will be determined. The neutral and ion winds will be measured to characterize the electrodynamical behavior of the MLTI. Oxygen and O2 abundances and nocticulent cloud activity will be measured. This review goes into the calibration and error sources, optical design, mechanisms design, detector design, electronics design, microprocessor and flight software design, and quality assurance and parts.

Killeen, Timothy L. (Principal Investigator)



Climate Time Machine  

NSDL National Science Digital Library

Go backward and forward in time with this interactive visualization that illustrates how the Earth's climate has changed in recent history. Topics covered are Sea Ice: ice cap extent 1979 - 2007, Sea Level: effect on coastal regions for each meter of sea level rise, Carbon Emissions: amount of annual fossil fuel emissions produced by the top 12 nations or regions from 1980-2004, and Average Global Temperature: a color-coded map showing the progression of changing global surface temperatures from 1885 to 2007.


Space-time qubits  

SciTech Connect

We construct a qubit algebra from field creation and annihilation operators acting on a global vacuum state. Particles to be used as qubits are created from the vacuum by a near-deterministic single-particle source. Our formulation makes the space-time dependence of the qubits explicit, preparing the way for quantum computation within a field framework. The method can be generalized to deal with interacting qubits whose wave packets are not perfectly matched to each other. We give an example of how to calculate the Heisenberg evolution of a simple two-qubit circuit, taking expectation values in the field vacuum state.

Pienaar, J. L.; Myers, C. R.; Ralph, T. C. [Centre for Quantum Computation and Communication Technology, School of Mathematics and Physics, University of Queensland, Brisbane 4072, Queensland (Australia)



A Matter of Time  

NASA Technical Reports Server (NTRS)

16 February 2006 This Mars Global Surveyor (MGS) Mars Orbiter Camera (MOC) image shows a portion of the south polar residual cap where the effects of sublimation are apparent. Over extended periods of time, sublimation 'eats' away at the smoother appearing material (largely composed of frozen carbon dioxide), darkening the scarps and creating the irregularly shaped depressions that are present throughout much of the scene.

Location near: 87.1oS, 69.3oW Image width: 3 km (1.9 mi) Illumination from: upper left Season: Southern Summer



Hope in Hard Times  

PubMed Central

In the face of challenging times, advocates for women and their families in maternal-child health care continue to promote evidence-based and mother-/baby-friendly care. What qualities allow childbirth educators, doulas, nurses, and perinatal care providers to keep going even when the health-care practices around them often do not match their values? This editorial explores the impact of recent trends in which increasing utilization of elective technology in maternity care may affect the individual commitment of childbirth advocates. Borrowing from research on successful advocates in other fields, the author speculates on both why and how childbirth advocates sustain commitment and how “we will prevail.” PMID:19119328

Leslie, Mayri Sagady



Biotechnology Through Time  

NSDL National Science Digital Library

In this activity, learners investigate the history and development of agricultural biotechnology. This experience begins with a Bio-Fest, in which learners use their senses to make observations about root beer, assorted cheeses, bread and yogurt. Learners are encouraged to think about the process of making food and how it has changed over time. This leads to a discussion about biotechnology. Learners complete the lesson by researching and completing a timeline. This activity is featured on pp.7-8 (part of a lesson that begins on p.6) of the "Yesterday, Today and Tomorrow: Agricultural Biology" unit of study for grades 6-8.

Indianapolis, The C.



Longitude through time  

NASA Astrophysics Data System (ADS)

Earth scientists today have had no objective method of calculating what the palaeolongitudes of tectonic plates and other geological units were in the long eons prior to the oldest known hotspot trails, which are only of Cretaceous age (ca. 130 Ma). Before this time, palaeomagnetism is the only method by which to position plates quantitatively on the globe. Palaeomagnetic studies only directly yield latitudes and plate rotations, but the longitude uncertainty can be minimized by selecting an appropriate reference plate: if one can determine which plate has moved least, then it should be used as the reference plate. Africa has been nearly surrounded by mid- ocean ridges since the break-up of Pangea, and thus the ridge push forces should have roughly cancelled each other out. Moving hotspot-based plate motion models show minimal longitudinal motion for Africa (<10 degrees) for the past 130 million years, confirming the lack of significant longitudinal motion inferred from consideration of the plate driving forces. It is uncertain whether the 'zero-longitude' assumption about Africa holds before Pangea's break-up, but in the absence of better reference points, we have regarded zero longitudinal average motion for Africa as the best assumption. With this approach we have been able to demonstrate that virtually all Large Igneous Province (LIPs) for the last 300 million years project radially onto the edges of the African and Pacific Large Low Shear Velocity Province (LLSVPs) near the core-mantle-boundary (CMB). The LIPs must for this reason be derived from mantle plumes, and CMB heterogeneities must have remained quite stationary since the formation of Pangea. LIPs have erupted since Archean times and there is no reason to preclude that they were all derived from LLSVPs in the deep mantle. That inspired us to consider whether older LIP events would yield similar results. We attempt to reconstruct Gondwana in longitude in Cambrian times based on the substantial Antrim plateau volcanics (Australia), a LIP of ca. 510 Ma age along the Gondwanan margin. If the LIP was formed at the margin of the Africa or Pacific LLSVPs and they have remained the same throughout Earth's history there are six possible marginal sites on the CMB from which to choose, but three sites that do not position the long- lived subduction margin of Gondwana (e.g. South America, East Antarctica and East Australia) above regions of high seismic velocity (the subduction graveyards) can be eliminated. If, as recently postulated, there have only been one LLSVP (or upwelling zone) in Pre-Pangean time (Pacific LLSVP) that reduces longitude choices to two possible marginal sites on the CMB.

Torsvik, T. H.; Steinberger, B.; Cocks, R. L.



Time dependent Long's equation  

NASA Astrophysics Data System (ADS)

Long's equation describes steady-state two-dimensional stratified flow over terrain. Its numerical solutions under various approximations were investigated by many authors. Special attention was paid to the properties of the gravity waves that are predicted to be generated as a result. In this paper we derive a time-dependent generalization of this equation and investigate analytically its solutions under some simplifications. These results might be useful in the experimental analysis of gravity waves over topography and their impact on atmospheric modeling.

Humi, M.



Daylight Savings Time  

NSDL National Science Digital Library

The California Energy Commission summaries the history of daylight savings and why we use it at this website. Users can discover where and how other areas of the world change the time to deal with the varying sunlight throughout the year. The website summarizes Benjamin Franklin's and William Willett's ideas for saving energy. Individuals can discover how daylight savings can save energy, save lives, prevent traffic accidents, and prevent crime. Visitors can find a chart of the dates of daylight savings from 1990 to 2010.


Real time Faraday spectrometer  


This invention uses a dipole magnet to bend the path of a charged particle beam. As the deflected particles exit the magnet, they are spatially dispersed in the bend-plane of the magnet according to their respective momenta and pass to a plurality of chambers having Faraday probes positioned therein. Both the current and energy distribution of the particles is then determined by the non-intersecting Faraday probes located along the chambers. The Faraday probes are magnetically isolated from each other by thin metal walls of the chambers, effectively providing real time current-versus-energy particle measurements.

Smith, Jr., Tommy E. (Fremont, CA); Struve, Kenneth W. (Albuquerque, NM); Colella, Nicholas J. (Livermore, CA)



"Making it real" time.  


It has been 30 years since the first description of the polymerase chain reaction (PCR)--corresponding, coincidentally, with the year of the first issue of BioTechniques. Ensuing decades have seen remarkable advances in this revolutionary technique. Central to these approaches was the creation of paradigms for monitoring the progress of PCR amplification in real time. One of these seminal reports appeared in BioTechniques in 1997, establishing the double-strand-specific dye SYBR Green as a workhorse tool for continuous monitoring of DNA amplification. PMID:23905171

Vrana, Kent E



Pulsar Timing Arrays  

NASA Astrophysics Data System (ADS)

In the last decade, the use of an ensemble of radio pulsars to constrain the characteristic strain caused by a stochastic gravitational wave background has advanced the cause of detection of very low frequency gravitational waves (GWs) significantly. This electromagnetic means of GW detection, called Pulsar Timing Array (PTA), is reviewed in this paper. The principle of operation of PTA, the current operating PTAs and their status are presented along with a discussion of the main challenges in the detection of GWs using PTA.

Joshi, Bhal Chandra



The Sun in Time  

NASA Technical Reports Server (NTRS)

Leveraging funds from NASA's Initiative to Develop Education through Astronomy and Space Science (IDEAS) program, we combined the expertise of an archaeoastronomer, a solar scientist, and a teacher to trace humankind's view of the Sun and how that has changed, from the time of Stonehenge in about 1800 B.C.E., to the time of the Maya in 700 C.E., up to the modem era. Our program was aimed at middle-school students in an attempt to explain not only how science is done today, but how science has evolved from the observations of ancient societies. From these varied cultures, we touched on methods of observing the Sun, ideas of the composition of the Sun, and the relationship of the Sun to everyday life. Further, using the von Braun Astronomical Society's Planetarium in Huntsville, Alabama as a test-bed for the program, we illustrated concepts such as solstices, equinoxes, and local noon with approximately 800 eighth grade students from the local area. Our presentation to SEPA will include a description of NASA's IDEAS program and how to go about partnering with a NASA astronomer, some slides from our planetarium program and web-site, and some hands-on activities.

Adams, Mitzi L.; Bero, Elizabeth; Sever, Thomas L.



HAWC Timing Calibration  

E-print Network

The High-Altitude Water Cherenkov (HAWC) Experiment is a second-generation highsensitivity gamma-ray and cosmic-ray detector that builds on the experience and technology of the Milagro observatory. Like Milagro, HAWC utilizes the water Cherenkov technique to measure extensive air showers. Instead of a pond filled with water (as in Milagro) an array of closely packed water tanks is used. The event direction will be reconstructed using the times when the PMTs in each tank are triggered. Therefore, the timing calibration will be crucial for reaching an angular resolution as low as 0.25 degrees.We propose to use a laser calibration system, patterned after the calibration system in Milagro. Like Milagro, the HAWC optical calibration system will use ~1 ns laser light pulses. Unlike Milagro, the PMTs are optically isolated and require their own optical fiber calibration. For HAWC the laser light pulses will be directed through a series of optical fan-outs and fibers to illuminate the PMTs in approximately one half o...

Huentemeyer, Petra; Dingus, Brenda



Physics Back in TIME  

NASA Astrophysics Data System (ADS)

Recently, I came into possession of an unusual item: a collection of 1928 TIME magazines. I began flipping through the pages out of sheer curiosity—and was soon astonished by the scale and the depth of their physics coverage. Back then, TIME had a special "Science" section in almost every issue and devoted quite a bit of space to the events that would hardly be mentioned in any popular magazine these days. Some of them were fleeting and merely curious, some truly timeless. Many of the articles and notes were devoted to physics: the people, the discoveries, the inventions, the conventions. I found the reading both entertaining and enlightening and would like to offer a sampler here. I hope that these little tidbits of history will lighten up the classroom discussions and help inspire your students by reminding them that physics is a dynamic, ever-changing field to which they may well contribute one day. I have found that my own students love it when a little bit of history is brought up; it always generates interesting questions and seems to spark the students' interest in the topic.

Korsunsky, Boris



Causality between time series  

E-print Network

Given two time series, can one tell, in a rigorous and quantitative way, the cause and effect between them? Based on a recently rigorized physical notion namely information flow, we arrive at a concise formula and give this challenging question, which is of wide concern in different disciplines, a positive answer. Here causality is measured by the time rate of change of information flowing from one series, say, X2, to another, X1. The measure is asymmetric between the two parties and, particularly, if the process underlying X1 does not depend on X2, then the resulting causality from X2 to X1 vanishes. The formula is tight in form, involving only the commonly used statistics, sample covariances. It has been validated with touchstone series purportedly generated with one-way causality. It has also been applied to the investigation of real world problems; an example presented here is the cause-effect relation between two climate modes, El Ni\\~no and Indian Ocean Dipole, which have been linked to the hazards in f...

Liang, X San



Time-Delay Interferometry  

NASA Astrophysics Data System (ADS)

Equal-arm detectors of gravitational radiation allow phase measurements many orders of magnitude below the intrinsic phase stability of the laser injecting light into their arms. This is because the noise in the laser light is common to both arms, experiencing exactly the same delay, and thus cancels when it is differenced at the photo detector. In this situation, much lower level secondary noises then set the overall performance. If, however, the two arms have different lengths (as will necessarily be the case with space-borne interferometers), the laser noise experiences different delays in the two arms and will hence not directly cancel at the detector. In order to solve this problem, a technique involving heterodyne interferometry with unequal arm lengths and independent phase-difference readouts has been proposed. It relies on properly time-shifting and linearly combining independent Doppler measurements, and for this reason it has been called time-delay interferometry (TDI). This article provides an overview of the theory, mathematical foundations, and experimental aspects associated with the implementation of TDI. Although emphasis on the application of TDI to the Laser Interferometer Space Antenna (LISA) mission appears throughout this article, TDI can be incorporated into the design of any future space-based mission aiming to search for gravitational waves via interferometric measurements. We have purposely left out all theoretical aspects that data analysts will need to account for when analyzing the TDI data combinations.

Tinto, Massimo; Dhurandhar, Sanjeev V.



Time for Dust Storms  

NASA Technical Reports Server (NTRS)

MGS MOC Release No. MOC2-414, 7 July 2003

This is the dusty time of year for Mars. The Mars Global Surveyor (MGS) Mars Orbiter Camera (MOC) team has been anticipating for months that late June through July 2003 will be a time of large dust storms and considerable haze. As June turned to July, several large dust storms began popping up. Two examples are shown here in this mosaic of MOC daily global images from June 29, 2003. Near the center of this picture is a large dust storm engulfing southern Isidis Planitia. Toward the upper right (northeast) of the Isidis storm is another event in northern Elysium Planitia.

This view of a portion of Mars is illuminated by sunlight from the left. This is a simple cylindrical map projection, north is up. The large dark feature just left of center is Syrtis Major; the bright oval toward the bottom left is the giant Hellas impact basin, which is more than 2,000 km (more than 1200 miles) across. The white area at the bottom of the picture is the south polar seasonal frost cap, made up mostly of carbon dioxide. The wispy features at the top of the image are clouds over the martian northern plains.



Remapping time across space.  


Multiple lines of evidence indicate that visual attention's temporal properties differ between the left and right visual fields (LVF and RVF). Notably, recent electroencephalograph recordings indicate that event-related potentials peak earlier for LVF than for RVF targets on bilateral-stream rapid serial visual presentation (RSVP) identification tasks. Might this hastened neural response render LVF targets perceptually available sooner than RVF targets? If so, how might the visual system reconcile these timing differences to estimate simultaneity across the LVF and RVF? We approached these questions by presenting bilateral-stream RSVP displays that contained opposite-hemifield targets and requiring participants to judge both the targets' temporal order and simultaneity. The temporal order judgments (TOJs) revealed that participants perceived LVF targets ?134 ms sooner than RVF targets. This LVF hastening approximates a full cycle of visual attention's canonical ?10 Hz (?100 ms) temporal resolution. In contrast, performance on the simultaneity task did not exhibit the LVF hastening observed on the TOJ task, despite identical retinal stimulation across the two tasks. This finding rules out a stimulus-driven "bottom-up" explanation for the task-specific behavior. Moreover, error patterns across the two tasks revealed that, within the decision stage of simultaneity judgments, participants remapped LVF targets, but not RVF targets, to a later time in the RSVP sequence. Such hemifield-specific remapping would effectively compensate for the cross-hemifield asymmetries in neural response latencies that could otherwise impair simultaneity estimates. PMID:23818678

Matthews, Nestor; Welch, Leslie; Festa, Elena; Clement, Andrew



Timing of cyber conflict.  


Nations are accumulating cyber resources in the form of stockpiles of zero-day exploits as well as other novel methods of engaging in future cyber conflict against selected targets. This paper analyzes the optimal timing for the use of such cyber resources. A simple mathematical model is offered to clarify how the timing of such a choice can depend on the stakes involved in the present situation, as well as the characteristics of the resource for exploitation. The model deals with the question of when the resource should be used given that its use today may well prevent it from being available for use later. The analysis provides concepts, theory, applications, and distinctions to promote the understanding strategy aspects of cyber conflict. Case studies include the Stuxnet attack on Iran's nuclear program, the Iranian cyber attack on the energy firm Saudi Aramco, the persistent cyber espionage carried out by the Chinese military, and an analogous case of economic coercion by China in a dispute with Japan. The effects of the rapidly expanding market for zero-day exploits are also analyzed. The goal of the paper is to promote the understanding of this domain of cyber conflict to mitigate the harm it can do, and harness the capabilities it can provide. PMID:24474752

Axelrod, Robert; Iliev, Rumen



Particles, space, and time  

NASA Astrophysics Data System (ADS)

Our Universe consistes of particles, space and time. Ever since Descartes we have known that true emptiness cannot exist; ever since Einstein we have known that space and time are part of the stuff of our world. Efforts to determine the structure of particles go in parallel with the search for the structure of spacetime. Einstein gave us a geometrical answer regarding the structure of spacetime: a distance recipe (Lorentz-Minkowski) suffices. The theory boils down to a patching together of local Lorentz frames into a global whole, which gives it the form of a gauge field theory based on local Lorentz symmetry. On large scales, the Einstein Equation seems to work well. The structure of particles is described by a gauge field. too. On small scales the ‘Standard Model’ seems to work very well. However, we know from Newtonian gravity that the presence of particles must be related to the structure of spacetime. Einstein made a conjecture for the form of this connection using the Newtonian limit of small speeds and weak fields. The right hand side of his equation for the bulk theory of matter (the energy-momentum tensor), is equated to the Einstein tensor from non-Euclidian geometry. But that connection is wrong. The structure of spacetime cannot be equated to the density of particles if we include the Standard Model in the matter tensor. In field theory a potential is not something that can be freely changed by adding an arbitrary scalar term; due to the local (as opposed to global) character of the fields, a potential becomes an entity in itself. Einstein's conjecture runs into profound trouble because the reality of potentials implies that the zero point energy of the vacuum must be included in the Einstein equation. The net result is the appearance of a term equivalent to a cosmological constant A of stupendous size, some 10118 times the critical cosmic density. The crisis due to the zero point fluctuations in the energy-momentum tensor is a clash of titans: Einstein's geometrical ideas on spacetime structure vs the behaviour of particles and the vacuum discribed by Dirac and followers. Someone, or everyone, is wrong. In my opinion the straightforward quantization of spacetime will always be impossible because the usual particle symmetries (U(1), SU(2), SU(3) and relatives) connect fermions and bosons, whereas relativistic analogies of these symmetries (the Lorentz symmetry) says something about spacetime and not about particles.

Icke, Vincent



China Digital Times  

NSDL National Science Digital Library

Created and maintained by the Berkeley China Internet Project, the China Digital Times (CDT) is a "collaborative news website covering China's social and political transition and its emerging role in the world." With their outstanding team of editors and media specialists, the CDT should be considered one of the most compelling sites covering important news and developments across China. Much like a traditional newspaper website, visitors can scroll through news highlights culled from various international media sources, add comments to various news items, and also search the entire site for specific materials. Those users with specific thematic interests will want to move right away to the "Sections" area, which breaks down news items into areas that include politics, society, Taiwan, economy, and culture. Even more fine tuned features can be found in the "News Focus" area, which includes sections that address human rights, the information revolution, and the environment.


ETC: Exposure Time Calculator  

NASA Astrophysics Data System (ADS)

Written for the Wide-Field Infrared Survey Telescope (WFIRST) high-latitude survey, the exposure time calculator (ETC) works in both imaging and spectroscopic modes. In addition to the standard ETC functions (e.g. background and S/N determination), the calculator integrates over the galaxy population and forecasts the density and redshift distribution of galaxy shapes usable for weak lensing (in imaging mode) and the detected emission lines (in spectroscopic mode). The program may be useful outside of WFIRST but no warranties are made regarding its suitability for general purposes. The software is available for download; IPAC maintains a web interface for those who wish to run a small number of cases without having to download the package.

Hirata, Christopher M.; Gehrels, Neil; Kneib, Jean-Paul; Kruk, Jeffrey; Rhodes, Jason; Wang, Yun; Zoubian, Julien



Jazz Old Time Online  

NSDL National Science Digital Library

For fans of jazz, the Jazz Old Time site will be a fun way to listen to few well-known chestnuts from the early days of this musical idiom. Of course, those who don't know much about jazz will appreciate listening to a few new artists as well. The site features over 18,000 songs in the public domain, and visitors can browse through the selections by artists or take a look at a few sample playlists. As one might suspect, artists like King Oliver, Meade Lux Lewis, and Louis Armstrong are featured prominently, though early recordings from later artists, such as Stan Getz, are also available. The site might also be recommended to students in a music appreciation course.


The Geometry of Time  

NASA Astrophysics Data System (ADS)

A description of the geometry of space-time with all the questions and issues explained without the need for formulas. As such, the author shows that this is indeed geometry, with actual constructions familiar from Euclidean geometry, and which allow exact demonstrations and proofs. The formal mathematics behind these constructions is provided in the appendices. The result is thus not a textbook introducing readers to the theory of special relativity so they may calculate formally, but rather aims to show the connection with synthetic geometry. It presents the relation to projective geometry and uses this to illustrate the starting points of general relativity. Written at an introductory level for undergraduates, this novel presentation will also benefit teaching staff.

Liebscher, Dierck-Ekkehard



Time encoded radiation imaging  


The various technologies presented herein relate to detecting nuclear material at a large stand-off distance. An imaging system is presented which can detect nuclear material by utilizing time encoded imaging relating to maximum and minimum radiation particle counts rates. The imaging system is integrated with a data acquisition system that can utilize variations in photon pulse shape to discriminate between neutron and gamma-ray interactions. Modulation in the detected neutron count rates as a function of the angular orientation of the detector due to attenuation of neighboring detectors is utilized to reconstruct the neutron source distribution over 360 degrees around the imaging system. Neutrons (e.g., fast neutrons) and/or gamma-rays are incident upon scintillation material in the imager, the photons generated by the scintillation material are converted to electrical energy from which the respective neutrons/gamma rays can be determined and, accordingly, a direction to, and the location of, a radiation source identified.

Marleau, Peter; Brubaker, Erik; Kiff, Scott



A Journey Through Time  

NSDL National Science Digital Library

Noted photographer Frans Lanting opens the website dedicated to his most recent ambitious project with these words: "Seven years ago I stood at the tide line of an estuary and began a personal journey through time.ĂÂŻĂÂżĂ½ Auspicious words indeed, and this lovely exploration of what he found on this journey takes visitors on a "lyrical interpretation of life on Earth from its earliest beginnings to its present diversity.ĂÂŻĂÂżĂ½ As visitors click on the words "Start Journey" they will be taken through eighty six photographs which document the various physical landforms and processes from the Hawaiian Islands to the heights of the Himalayas. After clicking on each photo, visitors will be presented with an interactive timeline that locates the photo within a timeline of geologic history. Interested parties can also peruse the "More about LIFE" section to learn more about the equipment Lanting uses in his work, and how the project came to life.

Lanting, Frans


BBC: In Our Time  

NSDL National Science Digital Library

Many have asked the question: "How do we understand the world around us?" Truly, it is a question that has animated discussion from Beijing to Bogota over the millennia, and it's one that motivates Melvyn Bragg, host of the BBC program "In Our Time". Drawing on guests from around the world, Bragg takes on science, culture, religion, philosophy, and history. Visitors can click on the "Explore Archive" area to travel through past programs, organized by theme. The "Science Archive" section alone is a real triumph, and with programs like "Neuroscience: Does the brain rule the mind?" and "The Multiverse", a group of friends could start their own mini-salon of ideas around the computer. Moving on, visitors can also sign up to receive Bragg's online newsletter and subscribe to the program's podcast. Finally, visitors can also throw their own three cents into the ring by offering their own commentaries via the "Have Your Say" comment form.


Real time automated inspection  


A method and apparatus are described relating to the real time automatic detection and classification of characteristic type surface imperfections occurring on the surfaces of material of interest such as moving hot metal slabs produced by a continuous steel caster. A data camera transversely scans continuous lines of such a surface to sense light intensities of scanned pixels and generates corresponding voltage values. The voltage values are converted to corresponding digital values to form a digital image of the surface which is subsequently processed to form an edge-enhanced image having scan lines characterized by intervals corresponding to the edges of the image. The edge-enhanced image is thresholded to segment out the edges and objects formed by the edges by interval matching and bin tracking. Features of the objects are derived and such features are utilized to classify the objects into characteristic type surface imperfections. 43 figs.

Fant, K.M.; Fundakowski, R.A.; Levitt, T.S.; Overland, J.E.; Suresh, B.R.; Ulrich, F.W.



Time-Constrained Machine Translation  

Microsoft Academic Search

This paper defines the class of time-constrained applications: applications in which the user has limited time to process the system output. This class is differentiated\\u000a from real-time systems, where it is production time rather than comprehension time that is constrained. Examples of time-constrained MT\\u000a applications include the translation of multi-party dialogue and the translation of closed-captions. The constraints on comprehension

Janine Toole; Davide Turcato; Fred Popowich; Dan Fass; Paul Mcfetridge



Cell complexes through time  

NASA Astrophysics Data System (ADS)

The history of cell complexes is closely related to the birth and development of topology in general. Johann Benedict Listing (1802 - 1882) introduced the term 'topology' into mathematics in a paper published in 1847, and he also defined cell complexes for the first time in a paper published in 1862. Carl Friedrich Gauss (1777 - 1855) is often cited as the one who initiated these ideas, but he did not publish either on topology or on cell complexes. The pioneering work of Leonhard Euler (1707 - 1783) on graphs is also often cited as the birth of topology, and Euler's work was cited by Listing in 1862 as a stimulus for his research on cell complexes. There are different branches in topology which have little in common: point set topology, algebraic topology, differential topology etc. Confusion may arise if just 'topology' is specified, without clarifying the used concept. Topological subjects in mathematics are often related to continuous models, and therefore quite irrelevant to computer based solutions in image analysis. Compared to this, only a minority of topology publications in mathematics addresses discrete spaces which are appropriate for computer-based image analysis. In these cases, often the notion of a cell complex plays a crucial role. This paper briefly reports on a few of these publications. This paper is not intended to cover the very lively progress in cell complex studies within the context of image analysis during the last two decades. Basically it stops its historic review at the time when this subject in image analysis research gained speed in 1980 - 1990. As a general point of view, the paper indicates that image analysis contributes to a fusion of topological concepts, the geometric and the abstract cell structure approach and point set topology, which may lead towards new problems for the study of topologies defined on geometric or abstract cell complexes.

Klette, Reinhard



Page 1 of 3 Adding a Punch or Reconciling Time for Time Stamp and Time Clock  

E-print Network

Page 1 of 3 Adding a Punch or Reconciling Time for Time Stamp and Time Clock Users A punch will punch in and out. 1) Click My QuickNavs Tab. Select Reconcile Time . 2) If an employee does not appear employees, or employees based on last names. #12;Page 2 of 3 3) To view or reconcile the employee's time

Hutcheon, James M.


Time, Place, and Content 53 Time, Place, and Content  

E-print Network

Time, Place, and Content 53 Time, Place, and Content Jonathon D. Crystal University of Georgia The goal of this article is to integrate information about basic mechanisms of time perception with research on time-place learning and research on the discrimination of what, when, and where (WWW). Several

Cook, Robert


Response Time Analysis of Gang Scheduling for Real Time Systems  

E-print Network

Response Time Analysis of Gang Scheduling for Real Time Systems FabrĂ­cio A. B. Silva, Ernesto P investigates the application of gang scheduling-based algorithms for real time systems that contain multiple processors. We derive the worst-case response time analysis for gang scheduling with and without machine

Cirne, Walfredo


Calculating the Maximum Execution Time of Real-Time Programs  

Microsoft Academic Search

In real-time systems, the timing behavior is an important property of each task. It has to be guaranteed that the execution of a task does not take longer than the specified amount of time. Thus, a knowledge about the maximum execution time of programs is of utmost importance.

Peter P. Puschner; Christian Koza



Developing Improved Travel Time Reliability Measures For Real-time  

E-print Network

Developing Improved Travel Time Reliability Measures For Real-time And Archived ITS Data Applications Robert L. Bertini and Kate Lyman ITS Europe, Aalborg, Denmark June 20, 2007 #12; Travel time estimation more important Measure of consistency of trip's travel time Need for reliability indices More

Bertini, Robert L.


Real time polarimetric dehazing.  


Remote sensing is a rich topic due to its utility in gathering detailed accurate information from locations that are not economically feasible traveling destinations or are physically inaccessible. However, poor visibility over long path lengths is problematic for a variety of reasons. Haze induced by light scatter is one cause for poor visibility and is the focus of this article. Image haze comes about as a result of light scattering off particles and into the imaging path causing a haziness to appear on the image. Image processing using polarimetric information of light scatter can be used to mitigate image haze. An imaging polarimeter which provides the Stokes values in real time combined with a "dehazing" algorithm can automate image haze removal for instant applications. Example uses are to improve visual display providing on-the-spot detection or imbedding in an active control loop to improve viewing and tracking while on a moving platform. In addition, removing haze in this manner allows the trade space for a system operational waveband to be opened up to bands which are object matched and not necessarily restricted by scatter effects. PMID:23518739

Mudge, Jason; Virgen, Miguel



Variable camshaft timing system  

SciTech Connect

A variable camshaft timing system in combination with an internal combustion engine having at least one cylinder, a rotatable member such as a crankshaft, and an intake and exhaust valve coupled to an intake camshaft and an exhaust camshaft respectively, the system is described comprising: a pulley wheel fixedly attached at one end of each of the intake and exhaust camshafts and the crankshaft; belt means interconnecting each of the pulley wheels for transferring rotational motion from the crankshaft to the intake and exhaust camshafts; first and second idler arm means pivotally attached to the engine, each of the idler arm means having a pivoting arm, a cam follower arm and an idler wheel in operative contact with the belt means; positioning cam means operatively coupled to each of the cam follower arms of the idler arm means; a control means responsive to various engine operating parameters for generating motor control signals; and electric motor means responsive to the motor control signals and operatively coupled to rotate the positioning cams means for positioning each of the idler arm means for changing the relative rotational position between the input camshaft and the exhaust camshaft.

Sapienza, S.J.



Patient experience of time duration: strategies for 'slowing time' and 'accelerating time' in general practices.  


Approaches to time management in general practices characteristically focus on objective 'clock time', for example, through appointment scheduling. No less important, however, is how patients experience time duration. Time is experienced as having passed slowly (time prolongation), quickly (time compression) or in rough synchronization with clock time. Duration has been theorized to be positively associated with information processing. This paper builds on that theory to suggest how practices can influence patients' subjective experience of duration in the practice environment, for example, by making waiting times appear to quicken and consultations appear to slow. PMID:14731148

Buetow, Stephen



Setting Time Limits on Tests  

ERIC Educational Resources Information Center

It is shown how the time limit on a test can be set to control the probability of a test taker running out of time before completing it. The probability is derived from the item parameters in the lognormal model for response times. Examples of curves representing the probability of running out of time on a test with given parameters as a function…

van der Linden, Wim J.



Time's Ontic Voltage Craig Callender  

E-print Network

Time's Ontic Voltage Craig Callender Philosophy of time, as practiced throughout the last hundred venue for attacking questions about the nature of time--in sharp contrast to the primary venue slowly in philosophy of time.1 Since twentieth-century analytic philosophy as a whole often drew

Callender, Craig


The Length of Time's Arrow  

SciTech Connect

An unresolved problem in physics is how the thermodynamic arrow of time arises from an underlying time reversible dynamics. We contribute to this issue by developing a measure of time-symmetry breaking, and by using the work fluctuation relations, we determine the time asymmetry of recent single molecule RNA unfolding experiments. We define time asymmetry as the Jensen-Shannon divergencebetween trajectory probability distributions of an experiment and its time-reversed conjugate. Among other interesting properties, the length of time's arrow bounds the average dissipation and determines the difficulty of accurately estimating free energy differences in nonequilibrium experiments.

Feng, Edward H.; Crooks, Gavin E.



SLH Timing Belt Powertrain  

SciTech Connect

The main goal of this proposal was to develop and test a novel powertrain solution for the SLH hydroEngine?, a low-cost, efficient low-head hydropower technology. Nearly two-thirds of U.S. renewable electricity is produced by hydropower (EIA 2010). According to the U.S. Department of Energy; this amount could be increased by 50% with small hydropower plants, often using already-existing dams (Hall 2004). There are more than 80,000 existing dams, and of these, less than 4% generate power (Blankinship 2009). In addition, there are over 800 irrigation districts in the U.S., many with multiple, non-power, low-head drops. These existing, non-power dams and irrigation drops could be retrofitted to produce distributed, baseload, renewable energy with appropriate technology. The problem is that most existing dams are low-head, or less than 30 feet in height (Ragon 2009). Only about 2% of the available low-head hydropower resource in the U.S. has been developed, leaving more than 70 GW of annual mean potential low-head capacity untapped (Hall 2004). Natel Energy, Inc. is developing a low-head hydropower turbine that operates efficiently at heads less than 6 meters and is cost-effective for deployment across multiple low-head structures. Because of the unique racetrack-like path taken by the prime-movers in the SLH, a flexible powertrain is required. Historically, the only viable technological solution was roller chain. Despite the having the ability to easily attach blades, roller chain is characterized by significant drawbacks, including high cost, wear, and vibration from chordal action. Advanced carbon-#12;fiber-reinforced timing belts have been recently developed which, coupled with a novel belt attachment system developed by Natel Energy, result in a large reduction in moving parts, reduced mass and cost, and elimination of chordal action for increased fatigue life. The work done in this project affirmatively addressed each of the following 3 major uncertainties concerning a timing-belt based hydroEngine ?powertrain: 1. Can a belt handle the high torques and power loads demanded by the SLH? (Yes.) 2. Can the SLH blades be mounted to belt with a connection that can withstand the loads encountered in operation? (Yes.) 3. Can the belt, with blade attachments, live through the required cyclic loading? (Yes.) The research adds to the general understanding of sustainable small hydropower systems by using innovative system testing to develop and demonstrate performance of a novel powertrain solution, enabling a new type of hydroelectric turbine to be commercially developed. The technical effectiveness of the methods investigated has been shown to be positive through an extensive design and testing process accommodating many constraints and goals, with a major emphasis on high cycle fatigue life. Economic feasibility of the innovations has been demonstrated through many iterations of design for manufacturability and cost reduction. The project is of benefit to the public because it has helped to develop a solution to a major problem -- despite the large available potential for new low-head hydropower, high capital costs and high levelized cost of electricity (LCOE) continue to be major barriers to project development. The hydroEngine? represents a significant innovation, leveraging novel fluid mechanics and mechanical configuration to allow lower-cost turbine manufacture and development of low head hydropower resources.

Schneider, Abe



Dead-time optimized time-correlated photon counting instrument with synchronized, independent timing channels  

E-print Network

Dead-time optimized time-correlated photon counting instrument with synchronized, independent timing channels Michael Wahla and Hans-JĂĽrgen Rahn PicoQuant GmbH, Rudower Chaussee 29, D-12489 Berlin December 2006; accepted 19 February 2007; published online 23 March 2007 Time-correlated single photon

Enderlein, Jörg


First-passage-time problems in time-aware networks  

E-print Network

First passage time or the first time that a stochastic process crosses a boundary is a random variable whose probability distribution is sought in engineering, statistics, finance, and other disciplines. The probability ...

Suwansantisuk, Watcharapan, 1978-




Library of Congress Historic Buildings Survey, Historic Engineering Record, Historic Landscapes Survey

51. LINES AT TIME OFFICE NO. 13 AT CHECKOUT TIME. SEAPLANE HANGARS (BLDGS. 1-2) IN BACKGROUND. USN PHOTO, JULY 11, 1941. - Quonset Point Naval Air Station, Roger Williams Way, North Kingstown, Washington County, RI


Timing with NuSTAR  

NASA Astrophysics Data System (ADS)

We present an overview of timing studies with NuSTAR. We start from the current status of the NuSTAR timing calibration focusing on three main topics: relative time precision, absolute time precision and dead time correction. Then, we review the use of timing in some interesting scientific results of the mission, including, but not limited to: the timing of rotation-powered pulsars and magnetars, measuring the spin evolution of these neutron stars; the phase-resolved study of cyclotron resonance scattering features (CRSFs) in accreting X-ray pulsars, yielding a measure of the magnetic field close in the accretion column close to the surface; the study of aperiodic variability and quasi-periodic oscillations in several accreting black holes and neutron stars, giving a measure of the relevant time scales around the accreting objects and independent constraints on the spectral models. For the latter, we make use of novel timing techniques specifically adapted to NuSTAR.

Bachetti, Matteo


Connecting Real-Time and Non-Real-Time Components  

Microsoft Academic Search

In this paper we describe a solution to the problem of communication between real-time and non-real-time compo- nents in a split container architecture. The split architecture carries forward an experience we gained in the The Dresden Real-Time Operating System Project (DROPS) (8): Often, only small parts of applications need to be real-time capable. Furthermore, often these parts require only a

Martin Pohlack; Ronald Aigner; Hermann Härtig


TimeScape: a time machine for the desktop environment  

Microsoft Academic Search

This paper describes a new desktop metaphor\\/system called TimeScape. A user of TimeScape can spatially arrange information on the desktop. Any desktop item can be removed at any time, and the system supports time-travel to the past or the future of the deskktop. The combination of spatial information arrangement and chronological navigation allows the user to organize and archive electric

Jun Rekimoto



Pressure transfer function in time and time-frequency domains  

Microsoft Academic Search

In this paper, we define a time-domain pressure transfer function calculated from SIWEH (smoothed instantaneous wave energy history) transforms, and a time-frequency domain pressure transfer function calculated from wavelet transforms, of synchronized wave and pressure data. It is our objective to study whether the time-domain pressure transfer function and the time-frequency domain pressure transfer function can provide new interpretation of

Min-Chih Huang; Cheng-Han Tsai



Eventually Infinite Time Turing Machine Degrees: Infinite Time Decidable Reals  

Microsoft Academic Search

We characterise explicitly the decidable predicates on integers of Infinite Time Turing machines, in terms of admissibility theory and the constructible hierarchy. We do this by pinning down $\\\\zeta$, the least ordinal not the length of any eventual output of an Infinite Time Turing machine (halting or otherwise); using this the Infinite Time Turing Degrees are considered, and it is

Philip D. Welch



The Time Famine: Toward a Sociology of Work Time  

Microsoft Academic Search

This paper describes a qualitative study of how people use their time at work, why they use it this way, and whether their way of using time is optimal for them or their work groups. Results of a nine-month field study of the work practices of a software engineering team revealed that the group's collective use of time perpetuated its

Leslie A. Perlow



Time in the Mind: Using Space to Think about Time  

ERIC Educational Resources Information Center

How do we construct abstract ideas like justice, mathematics, or time-travel? In this paper we investigate whether mental representations that result from physical experience underlie people's more abstract mental representations, using the domains of space and time as a testbed. People often talk about time using spatial language (e.g., a "long"…

Casasanto, Daniel; Boroditsky, Lera



50 Years of Time Parallel Time Integration Martin J. Gander  

E-print Network

how time domain decomposition methods were invented, and give an overview of the existing techniques and direct time parallel methods. We show for each of these techniques the main inventions over time. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 20 3.4 Gander, Halpern and Nataf 1999 . . . . . . . . . . . . . . . . . . . . . 21 3.5 Recent

Gander, Martin J.


April 2008 BEE CULTURE 43 Package timePackage time  

E-print Network

April 2008 BEE CULTURE 43 Package timePackage time Jennifer Berry It of March. This month bees are being shook by the millions into packages (weather dependent of course then you should be first in line for your bees. If you haven't placed an order you may have a hard time

Delaplane, Keith S.


Vehicle dispatching with time-dependent travel times  

Microsoft Academic Search

Abstract Most of the models for vehicle routing reported in the literature assume constant travel times. Clearly, ignoring the fact that the travel time between two locations does not depend only on the distance traveled, but on many other factors including the time of the day, impact the application of these models to real-world problems. In this paper, we present

Soumia Ichoua; Michel Gendreau; Jean-yves Potvin



Time Evolution in Dynamical Spacetimes  

E-print Network

We present a gauge--theoretical derivation of the notion of time, suitable to describe the Hamiltonian time evolution of gravitational systems. It is based on a nonlinear coset realization of the Poincar\\'e group, implying the time component of the coframe to be invariant, and thus to represent a metric time. The unitary gauge fixing of the boosts gives rise to the foliation of spacetime along the time direction. The three supressed degrees of freedom correspond to Goldstone--like fields, whereas the remaining time component is a Higgs--like boson.

A. Tiemblo; R. Tresguerres



EDITORIAL: Interesting times  

NASA Astrophysics Data System (ADS)

`May you live in interesting times' - old Chinese curse. First, many thanks to John Avison, the retiring Honorary Editor, for his hard work over the last five years, and the steady development in style and content under his stewardship. I can only hope to live up to the standards that he set. The next five years will take us into a new millenium, an event preceded - in England and Wales at least - by a period of stability, reflection and consolidation in education. Or so we are told - but whether such a self-denying ordinance will actually be maintained by the Government both before and after an election in 1997 remains to be seen. Nevertheless, we shall be thankful for any mercies, however small, that permit forward thinking rather than instant response. One of the things that readers of a journal called Physics Education should be thinking about is the continued decline in the numbers of students studying physics post-16. This is not a purely local phenomenon; most European countries are finding a similar decline. There are exceptions, of course: in Scotland numbers studying physics for Highers are increasing. Is such a decline a good thing or a bad thing? Only a minority of post-16 physics students go on to use the bulk of what they have learned in further studies or vocations. Does a knowledge and understanding of physics contribute to the mental well-being and cultural level - let alone material comfort - of any except those who use physics professionally? Is physics defensible as a contribution to the mental armoury of the educated citizen - compared with chemistry, biology - or Latin, say? Or should one rephrase that last question as `Is physics as we teach it today defensible...?' Such questions, and many others no doubt, may well be in the mind of the new Curriculum Officer appointed by the Institute of Physics `to engage in a wide-ranging consultation throughout the entire physics community on the nature and style of post-16 physics programmes, with a view to establishing a major curriculum development exercise on the scale of the Nuffield programmes of the 1960s'. The person appointed in this challenging role is the redoubtable Bryan Chapman (see his letter on page 14). I feel that readers of this journal constitute a well-informed section of the physics community and should be able to make a significant contribution to his work. I intend to use part of the July issue of Physics Education as a forum for views on the nature and style of post-16 (and even relevant pre-l6) physics programmes, both as they are and as they should be. The aim of the forum is not to provide solutions presented in lengthy, fully researched and well-argued articles but to raise ideas (and even expectations), to stimulate debate and set physics educators thinking creatively and radically about what might be an appropriate education in physics for the 2lst century. So send in your views - brief and to the point, trenchant and opinionated (all the more likely to be appreciated by Bryan C), anecdotal and theoretical, but preferably impregnated with the smell of chalk, wet blackboards, the sounds of wobbly-wheeled mechanics trolleys, quietly sizzling resistors and where necessary the heat of close encounters with the National Curriculum (version X) and/or GNVQs and the Subject Core for A-levels. Overseas readers - and Scots - may like to proffer advice based on their own, possibly less rebarbative, experiences. Don't hesitate: there is not a moment to be lost!

Dobson Honorary Editor, Ken



Time and timing in the acoustic recognition system of crickets.  


The songs of many insects exhibit precise timing as the result of repetitive and stereotyped subunits on several time scales. As these signals encode the identity of a species, time and timing are important for the recognition system that analyzes these signals. Crickets are a prominent example as their songs are built from sound pulses that are broadcast in a long trill or as a chirped song. This pattern appears to be analyzed on two timescales, short and long. Recent evidence suggests that song recognition in crickets relies on two computations with respect to time; a short linear-nonlinear (LN) model that operates as a filter for pulse rate and a longer integration time window for monitoring song energy over time. Therefore, there is a twofold role for timing. A filter for pulse rate shows differentiating properties for which the specific timing of excitation and inhibition is important. For an integrator, however, the duration of the time window is more important than the precise timing of events. Here, we first review evidence for the role of LN-models and integration time windows for song recognition in crickets. We then parameterize the filter part by Gabor functions and explore the effects of duration, frequency, phase, and offset as these will correspond to differently timed patterns of excitation and inhibition. These filter properties were compared with known preference functions of crickets and katydids. In a comparative approach, the power for song discrimination by LN-models was tested with the songs of over 100 cricket species. It is demonstrated how the acoustic signals of crickets occupy a simple 2-dimensional space for song recognition that arises from timing, described by a Gabor function, and time, the integration window. Finally, we discuss the evolution of recognition systems in insects based on simple sensory computations. PMID:25161622

Hennig, R Matthias; Heller, Klaus-Gerhard; Clemens, Jan



Time and timing in the acoustic recognition system of crickets  

PubMed Central

The songs of many insects exhibit precise timing as the result of repetitive and stereotyped subunits on several time scales. As these signals encode the identity of a species, time and timing are important for the recognition system that analyzes these signals. Crickets are a prominent example as their songs are built from sound pulses that are broadcast in a long trill or as a chirped song. This pattern appears to be analyzed on two timescales, short and long. Recent evidence suggests that song recognition in crickets relies on two computations with respect to time; a short linear-nonlinear (LN) model that operates as a filter for pulse rate and a longer integration time window for monitoring song energy over time. Therefore, there is a twofold role for timing. A filter for pulse rate shows differentiating properties for which the specific timing of excitation and inhibition is important. For an integrator, however, the duration of the time window is more important than the precise timing of events. Here, we first review evidence for the role of LN-models and integration time windows for song recognition in crickets. We then parameterize the filter part by Gabor functions and explore the effects of duration, frequency, phase, and offset as these will correspond to differently timed patterns of excitation and inhibition. These filter properties were compared with known preference functions of crickets and katydids. In a comparative approach, the power for song discrimination by LN-models was tested with the songs of over 100 cricket species. It is demonstrated how the acoustic signals of crickets occupy a simple 2-dimensional space for song recognition that arises from timing, described by a Gabor function, and time, the integration window. Finally, we discuss the evolution of recognition systems in insects based on simple sensory computations. PMID:25161622

Hennig, R. Matthias; Heller, Klaus-Gerhard; Clemens, Jan



Time, Calendars, and the Millennium.  

ERIC Educational Resources Information Center

Presents a list of resources that focus on the concept of time, telling time, and calendars. Includes nonfiction books for librarians, teachers and older readers; books for younger readers; poems; trivia; Web sites; and search sites. (AEF)

Barron, Daniel D.



Time Warp Operating System (TWOS)  

NASA Technical Reports Server (NTRS)

Designed to support parallel discrete-event simulation, TWOS is complete implementation of Time Warp mechanism - distributed protocol for virtual time synchronization based on process rollback and message annihilation.

Bellenot, Steven F.



Time Reference in Different Cultures.  

ERIC Educational Resources Information Center

Discusses time references in Russian- and English-speaking cultures by means of Russian translation variants of works by twentieth-century English-language writers. Suggests the different attitudes toward time as manifested by these two distinct cultures. (HB)

Khairullin, Vladimir



Telling Time With Analog Clocks.  

NSDL National Science Digital Library

Telling time is an important skill that you will use on a daily basis. It is important to understand and know how to read both analog clocks and digital clocks because they are both still used today. Analog clocks are becoming more out of date, but you don't ever want to be in a situation where you have to say "I can't read that kind of clock! I don't know what time it is." Let's practice your skills of telling time with analog clocks to help you avoid those situations. Move the hands of the clock to show the correct time. Time Clock See if you can match the analog time with the digital time. Match Analog and Digital When you get to this page, click the random button and then practice telling the analog time. If level one is too easy, then try levels ...

Alyssa Nichols



Talking with Children about Time.  

ERIC Educational Resources Information Center

Provides activities to help preschool children develop an understanding of the concept of time. Activities include making a sundial and a water clock or sand clock, as well as a time wheel of the months and seasons. (HTH)

Texas Child Care, 1995



Fractal and natural time analysis of geoelectrical time series  

NASA Astrophysics Data System (ADS)

In this work we show the analysis of geoelectric time series linked with two earthquakes of M=6.6 and M=7.4. That time series were monitored at the South Pacific Mexican coast, which is the most important active seismic subduction zone in México. The geolectric time series were analyzed by using two complementary methods: a fractal analysis, by means of the detrended fluctuation analysis (DFA) in the conventional time, and the power spectrum defined in natural time domain (NTD). In conventional time we found long-range correlations prior to the EQ-occurrences and simultaneously in NTD, the behavior of the power spectrum suggest the possible existence of seismo electric signals (SES) similar with the previously reported in equivalent time series monitored in Greece prior to earthquakes of relevant magnitude.

Ramirez Rojas, A.; Moreno-Torres, L. R.; Cervantes, F.



A comment on the use of flushing time, residence time, and age as transport time scales  

USGS Publications Warehouse

Applications of transport time scales are pervasive in biological, hydrologic, and geochemical studies yet these times scales are not consistently defined and applied with rigor in the literature. We compare three transport time scales (flushing time, age, and residence time) commonly used to measure the retention of water or scalar quantities transported with water. We identify the underlying assumptions associated with each time scale, describe procedures for computing these time scales in idealized cases, and identify pitfalls when real-world systems deviate from these idealizations. We then apply the time scale definitions to a shallow 378 ha tidal lake to illustrate how deviations between real water bodies and the idealized examples can result from: (1) non-steady flow; (2) spatial variability in bathymetry, circulation, and transport time scales; and (3) tides that introduce complexities not accounted for in the idealized cases. These examples illustrate that no single transport time scale is valid for all time periods, locations, and constituents, and no one time scale describes all transport processes. We encourage aquatic scientists to rigorously define the transport time scale when it is applied, identify the underlying assumptions in the application of that concept, and ask if those assumptions are valid in the application of that approach for computing transport time scales in real systems.

Monsen, N.E.; Cloern, J.E.; Lucas, L.V.; Monismith, S.G.



Real-Time Operating Systems  

Microsoft Academic Search

\\u000a This section is devoted to real-time operating systems (RTOS) for supporting applications with real-time requirements. In\\u000a these applications, most real-time requirements are derived form the physics of the environment that is being controlled or\\u000a monitored and this implies that most real-time systems are embedded computer systems, and that an RTOS has to provide facilities\\u000a for supporting embedded applications. There are

Bruno Bouyssounouse; Joseph Sifakis


7 Tips for Time Management  

NSDL National Science Digital Library

Faculty life is full of diverse duties and responsibilities that can become overwhelmingly time-consuming. "Multitasking" just means reducing the attention and the quality of our focus on individual tasks. There is nothing you can do to get more time. Learning to control your time, however, may be a significant factor in your job success. Maybe your work life could benefit from the application of some time management tips specific to the faculty workload.

University of South Carolina (University of South Carolina)



Tech Trek: Time for class  

NSDL National Science Digital Library

One of the most abstract concepts that you will teach to your students is the concept of time. Usually introduced at the beginning of the school year, the concept of time is taught along with measurements and scientific units such as length, mass, and volume. However, unlike length, mass, and volume, time can be a very confusing concept to understand. This overview of the concept of time also links to internet resources and includes several classroom extension ideas.

Christmann, Edwin P.



Time Dependence in Plasma Codes  

E-print Network

Time-dependent plasma codes are a natural extension of static nonequilibrium plasma codes. Comparing relevant timescales will determine whether or not time-dependent treatment is necessary. In this article I outline the ingredients for a time-dependent plasma code in a homogeneous medium and discuss the computational method. In the second half of the article I describe recombination in the early Universe as a detailed example of a problem whose solution requires a time-dependent plasma code.

S. Seager



Entropy of electromyography time series  

NASA Astrophysics Data System (ADS)

A nonlinear analysis based on Renyi entropy is applied to electromyography (EMG) time series from back muscles. The time dependence of the entropy of the EMG signal exhibits a crossover from a subdiffusive regime at short times to a plateau at longer times. We argue that this behavior characterizes complex biological systems. The plateau value of the entropy can be used to differentiate between healthy and low back pain individuals.

Kaufman, Miron; Zurcher, Ulrich; Sung, Paul S.



Consensus on Learning Time Builds  

ERIC Educational Resources Information Center

Under enormous pressure to prepare students for a successful future--and fearful that standard school hours do not offer enough time to do so--educators, policymakers, and community activists are adding more learning time to children's lives. Twenty-five years ago, the still-resonant report "A Nation at Risk" urged schools to add more time--an…

Gewertz, Catherine



Time resolved techniques: An overview  

SciTech Connect

Synchrotron sources provide exceptional opportunities for carrying out time-resolved x-ray diffraction investigations. The high intensity, high angular resolution, and continuously tunable energy spectrum of synchrotron x-ray beams lend themselves directly to carrying out sophisticated time-resolved x-ray scattering measurements on a wide range of materials and phenomena. When these attributes are coupled with the pulsed time-structure of synchrotron sources, entirely new time-resolved scattering possibilities are opened. Synchrotron beams typically consist of sub-nanosecond pulses of x-rays separated in time by a few tens of nanoseconds to a few hundred nanoseconds so that these beams appear as continuous x-ray sources for investigations of phenomena on time scales ranging from hours down to microseconds. Studies requiring time-resolution ranging from microseconds to fractions of a nanosecond can be carried out in a triggering mode by stimulating the phenomena under investigation in coincidence with the x-ray pulses. Time resolution on the picosecond scale can, in principle, be achieved through the use of streak camera techniques in which the time structure of the individual x-ray pulses are viewed as quasi-continuous sources with {approximately}100--200 picoseconds duration. Techniques for carrying out time-resolved scattering measurements on time scales varying from picoseconds to kiloseconds at present and proposed synchrotron sources are discussed and examples of time-resolved studies are cited. 17 refs., 8 figs.

Larson, B.C.; Tischler, J.Z.



Time translation of quantum properties  

E-print Network

Based on the notion of time translation, we develop a formalism to deal with the logic of quantum properties at different times. In our formalism it is possible to enlarge the usual notion of context to include composed properties involving properties at different times. We compare our results with the theory of consistent histories.

L. Vanni; R. Laura



Bonneville, Power Administration Timing System  

NASA Technical Reports Server (NTRS)

Time is an integral part of the Bonneville Power Administration's (BPA) operational systems. Generation and power transfers are planned in advance. Utilities coordinate with each other by making these adjustments on a timed schedule. Price varies with demand, so billing is based on time. Outages for maintenance are scheduled to assure they do not interrupt reliable power delivery. Disturbance records are aligned with recorded timetags for analysis and comparison with related information. Advanced applications like traveling wave fault location and real-time phase measurement require continuous timing with high precision. Most of BPA is served by a Central Time System (CTS) at the Dittmer Control Center near Portland, OR. This system keeps time locally and supplies time to both the control center systems and field locations via a microwave signal. It is kept synchronized to national standard time and coordinated with interconnected utilities. It is the official BPA time. Powwer system control and operation is described, followed by a description of BPA timing systems including CTS, the Fault Location Acquisition Reporter, time dissemination, and phasor measurements. References are provided for further reading.

Martin, Kenneth E.



Timing of major transportation investments  

Microsoft Academic Search

This report offers a broad overview of timing research as it applies to major transportation investments. Specific emphasis is given to major public transit investments. The report is designed to provide planners and decision-makers with a better understanding of timing research. The report emphasizes basic economic principles of investment timing rather than detailed techniques. The purpose of this particular report

Xuehao Chu; S. Polzin