Locked Wheel Research Articles

Distinct stages of adult hippocampal neurogenesis are regulated by running and the running environment

Hippocampal neurogenesis continues into adulthood in mammalian vertebrates, and in experimental rodent models it is powerfully stimulated by exposure to a voluntary running wheel. In this study, we demonstrate that exposure to a running wheel environment, in the absence of running, is sufficient to regulate specific aspects of hippocampal neurogenesis. Adult mice were provided with standard housing, housing enriched with a running wheel or housing enriched with a locked wheel (i.e., an environment comparable to that of running animals, without the possibility of engaging in running). We found that mice in the running wheel and locked wheel groups exhibited equivalent increases in proliferation within the neurogenic niche of the dentate gyrus; this included comparable increases in the proliferation of radial glia-like stem cells and the number of proliferating neuroblasts. However, only running animals displayed increased numbers of postmitotic neuroblasts and mature neurons. These results demonstrate that the running wheel environment itself is sufficient for promoting proliferation of early lineage hippocampal precursors, while running per se enables newly generated neuroblasts to survive and mature into functional hippocampal neurons. Thus, both running-independent and running-dependent stimuli are integral to running wheel-induced hippocampal neurogenesis.

An Intelligent Regenerative Braking Strategy for Electric Vehicles

Regenerative braking is an effective approach for electric vehicles (EVs) to extend their driving range. A fuzzy-logic-based regenerative braking strategy (RBS) integrated with series regenerative braking is developed in this paper to advance the level of energy-savings. From the viewpoint of securing car stability in braking operations, the braking force distribution between the front and rear wheels so as to accord with the ideal distribution curve are considered to prevent vehicles from experiencing wheel lock and slip phenomena during braking. Then, a fuzzy RBS using the driver’s braking force command, vehicle speed, battery SOC, battery temperature are designed to determine the distribution between friction braking force and regenerative braking force to improve the energy recuperation efficiency. The experimental results on an “LF620” prototype EV validated the feasibility and effectiveness of regenerative braking and showed that the proposed fuzzy RBS was endowed with good control performance. The maximum driving range of LF620 EV was improved by 25.7% compared with non-RBS conditions.

Research on Configuration Design Method of Mass Customization Product Based-on Function-Structure Model

Considering the problem that current configuration design method is mainly faced for professionals, based-on the analysis of different customers’ respective understanding of products and configuration methods, a function-structure configuration method of mass customization product is proposed according to the general design process from function to structure. Meanwhile, in the configuration real-time related analyses and advices are provided customers, which would guide customers to complete configuration design of personal product rapidly. Finally, a wheel lock configuration case is given to illustrate the proposed method.

Key Factors Effect on Vehicle Braking Performance Based on Nonlinear 3DOF Vehicle Dynamic Model

3DOF nonlinear braking dynamic model considering tire-road adhesion characteristics was established, and non-dimensional equations were gained from the above mathematic models by using braking torque coefficient, front and rear axle equivalent inertia coefficients and braking force distribution coefficient. Based on the numerical calculation in Matlab-Simulink software, the effect of key factors, (including vehicle mass and vehicle gravity center position variation, frontal and rear braking force distribution coefficient, and frontal and rear axle inertial variation caused by driven mode) on vehicle braking performance, such as braking distance and wheel lockup status, was investigated and summarized. Several 3D visualizations of the simulation results show that variation of vehicle center of gravity, vehicle mass, braking moment distribution, wheel equivalent inertia due to driveline, can cause quite complex effect. It can be assumed that the gained results in this study can help to improve vehicle braking performance and enhance braking stability.

Reduction of extinction and reinstatement of cocaine seeking by wheel running in female rats

Previous work has shown that wheel running reduced the maintenance of cocaine self-administration in rats. In the present study, the effect of wheel running on extinction and reinstatement of cocaine seeking was examined. Female rats were trained to run in a wheel during 6-h sessions, and they were then catheterized and placed in an operant conditioning chamber where they did not have access to the wheel but were allowed to self-administer iv cocaine. Subsequently, rats were divided into four groups and were tested on the extinction and reinstatement of cocaine seeking while they had varying access to a wheel in an adjoining compartment. The four groups were assigned to the following wheel access conditions: (1) wheel running during extinction and reinstatement (WER), (2) wheel running during extinction and a locked wheel during reinstatement (WE), (3) locked wheel during extinction and wheel running during reinstatement (WR), and (4) locked wheel during extinction and reinstatement (WL). WE and WR were retested later to examine the effect of one session of wheel access on cocaine-primed reinstatement. There were no group differences in wheel revolutions, in rate of acquisition of cocaine self-administration, or in responding during maintenance when there was no wheel access. However, during extinction, WE and WER responded less than WR and WL. WR and WER had lower cocaine-primed reinstatement than WE and WL. One session of wheel exposure in WE also suppressed cocaine-primed reinstatement. Wheel running immediately and effectively reduced cocaine-seeking behavior, but concurrent access to running was necessary. Thus, exercise is a useful and self-sustaining intervention to reduce cocaine-seeking behavior.

Evaluation of the Effect of Pavement Roughness on Skid Resistance

Roughness of a pavement surface is commonly correlated to its serviceability. On the other hand, on many occasions, investigators have attributed pavement roughness to inadequate skid resistance (friction) as well. However, current pavement friction evaluation and standardization models have yet to incorporate effects of pavement roughness. Hence a study was conducted to investigate and quantify the effects of pavement roughness on the skid number (SN) (or 100 coefficient of friction). First, an experimental program was executed to evaluate SN measured from a locked wheel tester (LWT) on pavement sections with similar micro- and macrotexture conditions but different levels of roughness. The measured average SN was seen to be significantly lower on relatively rougher pavement sections. To explain the above observations, a second set of experiments was conducted to study the effect of the normal load on the LWT tire on SN. Statistical analysis including regression and ANOVA was used to validate the nonlinear reciprocal relationship found between SN and the normal load which contradicts the general perception of constant SN with respect to the normal load. Then, a one-dimensional two-degrees-of-freedom vibration model was formulated to incorporate the significant dynamic fluctuations of the normal load of the LWT induced by pavement roughness and the vehicle speed. The variation of the normal load and its nonlinear relation to SN was used to explain lower SN values measured on relatively rougher surfaces. The feasibility of using the international roughness index and the dynamic load coefficient as predictors of the reduction in SN due to pavement roughness was also investigated. Assurance of adequate skid resistance is a vital factor considered in allocating pavement rehabilitation funds at the network level. Since excessively rough pavements also create skid hazards, it is concluded that roughness effects must be considered in pavement management systems not only for serviceability purposes, but also in safety evaluations.

Interactions between Procedural Learning and Cocaine Exposure Alter Spontaneous and Cortically Evoked Spike Activity in the Dorsal Striatum

We have previously shown that cocaine enhances gene regulation in the sensorimotor striatum associated with procedural learning in a running-wheel paradigm. Here we assessed whether cocaine produces enduring modifications of learning-related changes in striatal neuron activity, using single-unit recordings in anesthetized rats 1 day after the wheel training. Spontaneous and cortically evoked spike activity was compared between groups treated with cocaine or vehicle immediately prior to the running-wheel training or placement in a locked wheel (control conditions). We found that wheel training in vehicle-treated rats increased the average firing rate of spontaneously active neurons without changing the relative proportion of active to quiescent cells. In contrast, in rats trained under the influence of cocaine, the proportion of spontaneously firing to quiescent cells was significantly greater than in vehicle-treated, trained rats. However, this effect was associated with a lower average firing rate in these spontaneously active cells, suggesting that training under the influence of cocaine recruited additional low-firing cells. Measures of cortically evoked activity revealed a second interaction between cocaine treatment and wheel training, namely, a cocaine-induced decrease in spike onset latency in control rats (locked wheel). This facilitatory effect of cocaine was abolished when rats trained in the running wheel during cocaine action. These findings highlight important interactions between cocaine and procedural learning, which act to modify population firing activity and the responsiveness of striatal neurons to excitatory inputs. Moreover, these effects were found 24 h after the training and last drug exposure indicating that cocaine exposure during the learning phase triggers long-lasting changes in synaptic plasticity in the dorsal striatum. Such changes may contribute to the transition from recreational to habitual or compulsive drug taking behavior.

INTELLIGENT BRAKING SYSTEM USING FUZZY LOGIC AND SLIDING MODE CONTROLLER

In this paper, an antilock–antiskid braking system controller, which has been designed for stability enhancement of vehicles during braking and turning, is presented. Using available signals, a novel structure is proposed for vehicle stability improvement for critical driving conditions such as braking on slippery or µ-split road surfaces. In conventional vehicles, undesired lane changes may occur due to equal dispatch of braking torques to all wheels simultaneously. Also, intensive pressure on brake pedal can bring about wheel lockup which results in vehicle instability and undesired lane changes. Antilock braking system (ABS) along with Antiskid braking system (ASBS) can serve as a driver-assistance system in vehicle path correction facing critical driving conditions during braking and turning round on different road surfaces. For these purposes, at first, a trained Neuro-Fuzzy estimator is used for vehicle path prediction according to vehicle’s speed, applied steering angle and their changes. Then, slip of each wheel will be controlled by an antilock fuzzy controller which has been designed for each wheel. Also, a sliding mode controller has been designed so as to control the yaw angle considering the yaw error, where the yaw error is resulted from the difference of the Neuro-Fuzzy estimator’s output and actual yaw angle. Then, the difference of the left and the right wheels’ braking torques are used by the sliding mode controller in order to reduce the yaw error. Considering a model of three-degreeof-freedom for chassis and one-degree-of-freedom Dugoff’s tire model for each wheel, a series of Matlab/Simulink simulation results will be presented to validate the effectiveness of the proposed controller. Finally, a comparison will be made between the proposed method and one of the recent control systems which shows the superiority of its performance.

Speed Adjustment Factors for Locked-Wheel Skid Trailer Measurements

Locked-wheel trailers are the predominant friction-testing tool used by state departments of transportation in the United States. These trailers measure friction on a locked wheel on the wetted pavement surface as the wheel slides at a constant speed. The skid resistance is reported as the skid number (SN) at the speed it was measured, with the standard test speed at 40 mph. Speed on most rural interstate and primary roads is rarely lower than 65 mph, whereas in most urban environments, congestion, intersections, and high-traffic volumes can lead to average traffic speeds as low as 20 mph. A methodology was proposed to convert the skid numbers from one speed to any desired speed by using adjustment factors. The data used to develop this methodology came from measurements taken by members of the Pavement Surface Properties Consortium for the three consecutive years from 2007 to 2009. The adjustment factors were developed for the different flexible and continuously reinforced concrete pavement surfaces that are available at the Virginia Smart Road. The friction measurements performed with the skid testers presented different responses to the different pavement surface types. To separate them, principal component analysis was used, and three different groups of surfaces were identified. Principal component analysis was also used to develop a friction conversion method that used correlations between speed and texture. Correlations between speed factors and macrotexture were computed only for smooth tire skid testers, because ribbed tires do not exhibit good relationships, probably because measurements with this tire are not sensitive to macrotexture.

Measuring Friction of Patterned and Textured Pavements

The Florida Department of Transportation initiated a field study to compare the suitability of two friction-testing devices for measuring the friction characteristics of patterned and textured crosswalks: (a) a site-specific dynamic friction tester (DFT) and (b) a semicontinuous locked wheel tester. The locked wheel testing was performed with both ribbed and smooth tires at 20, 30, and 40 mph (30, 50 and 65 km/h), respectively. Ten test sections were randomly selected to include the different types of patterned and textured processes currently approved for use in Florida. The results of this study indicated that the smooth tire measurements were, generally, in good agreement with the DFT, regardless of test speed. The correlation between the DFT and the ribbed tire test improved with the increasing speed of the locked wheel testing. In addition, for a given test method, harmonization of different test speeds was also performed to allow for the speed conversion of the friction coefficients. The flexibility provided by these harmonization efforts is of great practical use in evaluating the frictional characteristics of patterned and textured crosswalks, especially when dealing with constraints such as speed limits. The testing program, the data collection effort, and the subsequent analyses and findings are described, as well as the lessons learned from Florida's experience with patterned and textured pavements.

Forensic Engineering Analysis Of Bicycle Versus Pickup Collision

The Forensic Engineering Analysis Of Bicycle-Vehicle Incidents Presents Its Own Unique Set Of Challenges. Often, The Forensic Engineer Is Faced With A Limited Data Set For Determining Vehicle Impact Speed From The Physical Evidence Produced By A Bicycle Collision With An Automobile, Which May Not Be Of Issue For A Vehicle-To-Vehicle Collision At Similar Speeds. This Paper Analyzes A Collision Between A Light Duty Pickup Pulling A Tandem Axle Utility Trailer And A Bicycle Ridden By A Minor Child. There Were Allegations That The Pickup Was Traveling At A High Speed Above The Speed Limit, As Well As Passing Another Vehicle At The Time Of The Incident. In Order To Accurately And Dependably Determine The Speed Of The Ford F350 Pickup Involved In This Incident Event, This Forensic Engineer Elected To Recreate The Vehicle Locked Wheel Skidding Evidence That Was Produced During The Incident Event And Photographically Recorded By Police Investigators. The Dynamic Skid Testing Technique, Test Equipment, And General Test Procedures Used To Accurately Determine Vehicle Speeds For This Incident Event, And How It Can Be Applied To Similar Collision Events Are Discussed In This Paper

Effects of access to voluntary wheel running on the development of stereotypy

Stereotyped motor behaviors are a common consequence of environmental restriction in a wide variety of species. Although environmental enrichment has been shown to substantially reduce stereotypy levels, the various components of enrichment have not been evaluated independently to determine which is responsible for this effect. Exercise, particularly voluntary wheel running, is a promising candidate based on several lines of behavioral and neurobiological evidence. To test the hypothesis that access to wheel running will reduce stereotyped motor behavior, we reared deer mice from weaning with continuous access to either a functional running wheel or a locked wheel. We assessed running behavior throughout this time period and stereotypy levels in a test context at 30 and 45 days post-weaning. We found that exercise did not significantly affect stereotypy level nor was there an association between wheel running and stereotypy. Thus, exercise alone, unlike environmental enrichment, does not prevent the development of stereotypy. These results have important implications for animal welfare.

Chlorpromazine specifically prevents the wheel-induced feeding suppression in rats

In rats, limited daytime wheel access suppresses feeding over the subsequent night [Lattanzio SB, Eikelboom R. Wheel access duration in rats: I. effects on feeding and running. Behav Neurosci 2003; 117:496–504.]. This phenomenon is known as the wheel-induced feeding suppression (WIFS). The classic antipsychotic, chlorpromazine, can minimize the severity of the related activity anorexia procedure, but is thought to act through a suppression of running [Routtenberg A. “Self-starvation” of rats living in activity wheels: adaptation effects. J Comp Physiol Psychol 1968; 66:234–8.]. We tested the effects of chlorpromazine (2 mg/kg IP) on the acute WIFS in 40 adult male rats by administering the drug before or after 3 h of daytime wheel access and measuring food consumption over the subsequent 24 h. Control groups received saline injections or were exposed to locked wheels. While chlorpromazine did not attenuate feeding or change wheel running alone, it blocked their interaction, the acute WIFS. This procedure might be useful in screening drugs for anorexia nervosa where exercise is often elevated and feeding is suppressed.

Automobile security concerns

Automotive theft and hijacking are traditionally the major automobile security concerns. The Federal Bureau of Investigation (FBI) Uniform Crime Reports (UCR) state that the number of automobiles stolen each year fluctuated around 1,200,000 from 1997 to 2006 (Figure 1), without having a steady trend. Common ways of stealing cars include carjacking, breaking windows or jimmying locks to gain entry, deactivating the alarm or steering wheel lock by cutting wires, deceiving manufacturers to make a replacement key by providing specific information of automobiles, or (most frequently) keys left in the automobile by their careless owners. Admittedly these threats are low tech. Well-known automotive security features, such as alarms, entry lock, and transmission or wheel lock, prevent the threats to some extent.

Methods to control wheel locks and wheel spins on low friction coefficient roads for front and rear wheel independent drive type electric vehicles (FRID EVs)

AbstractWheel lock and spin control methods suitable for front and rear wheel independent drive type electric vehicles (FRID EVs) are studied here. Wheel locks and spins occur easily when braking and driving operations such as deceleration and acceleration are performed on bad roads with low friction coefficient such as wet or frozen roads. The methods studied here are characterized by using the structural feature of FRID EVs which can freely distribute the driving and braking torques to front and rear wheels according to running and road surface conditions. These wheel locks and spins occurring when braking and driving on bad roads are controlled by properly distributing the braking and driving torques to front and rear wheels in consideration of the load movement caused by braking operations and slip ratios of the front and rear wheel sides. The effectiveness of the wheel lock and spin methods studied here is verified through simulations and experiments on various roads with a low friction coefficient using a prototype EV with the FRID structure. Copyright © 2009 Institute of Electrical Engineers of Japan. Published by John Wiley & Sons, Inc.

Field Calibration of an Analytical Model for Pavement Friction Testing Applications

Abstract Regular evaluation and maintenance of skid resistance (friction) of highway and runway pavements is an essential task in improving transportation safety. Various measuring devices operating under different mechanisms have been developed for friction evaluation. Generally, there is a significant variation of friction measurements provided by different devices on the same surface, requiring reliable guidelines for comparison of devices. This paper presents the results of a study conducted to verify whether the LuGre model, an existing dynamic friction model composed of physically significant parameters, would satisfy the above need. A revised formulation which would enhance the applicability of the average lumped version of the LuGre model to model real-world dynamic friction problems is also presented. The original LuGre model was applied to two widely used pavement friction measuring devices; the locked wheel skid trailer and the dynamic friction tester (DFT). In the work presented here the characteristic equations for each device have been formulated based on the LuGre model. In addition an analytical treatment of the kinetics of the DFT is performed to facilitate the application of the LuGre model to the DFT. For each device, the LuGre model parameters were tuned to match a part of the field data collected during a field test carried out by the authors. It was seen that the obtained parameters are reasonably comparable with those reported in the literature. Moreover, the calibrated model equations were seen to predict the observed data that were not used in model fitting, with acceptable accuracy. The results obtained in this study clearly show that the LuGre model can be utilized as an efficient physically intuitive tool with possible applications in: (1) predicting the three-dimensional variation of friction (with wheel slip and traveling speed) as measured by selected friction measuring devices, (2) providing physical interpretations to friction data from different devices, (3) regular self-calibration of friction devices, and (4) comparing pavement friction measurements from different devices.

Effects of two hospital bed design features on physical demands and usability during brake engagement and patient transportation: A repeated measures experimental study

Background Work-related musculoskeletal disorders (WMSDs) are prevalent among healthcare workers worldwide. While existing research has focused on patient-handling techniques during activities which require direct patient contact (e.g., patient transfer), nursing tasks also involve other patient-handling activities, such as engaging bed brakes and transporting patients in beds, which could render healthcare workers at risk of developing WMSDs. Objectives Effectiveness of hospital bed design features (brake pedal location and steering-assistance) was evaluated in terms of physical demands and usability during brake engagement and patient transportation tasks. Design Two laboratory-based studies were conducted. In simulated brake engagement tasks, three brake pedal locations (head-end vs. foot-end vs. side of a bed) and two hands conditions (hands-free vs. hands-occupied) were manipulated. Additionally, both in-room and corridor patient transportation tasks were simulated, in which activation of steering-assistance features (5th wheel and/or front wheel caster lock) and two patient masses were manipulated. Participants Nine novice participants were recruited from the local student population and community for each study. Methods During brake engagement, trunk flexion angle, task completion time, and questionnaires were used to quantify postural comfort and usability. For patient transportation, dependent measures were hand forces and questionnaire responses. Results Brake pedal locations and steering-assistance features in hospital beds had significant effects on physical demands and usability during brake engagement and patient transportation tasks. Specifically, a brake pedal at the head-end of a bed increased trunk flexion by 74–224% and completion time by 53–74%, compared to other pedal locations. Participants reported greater overall perceived difficulty and less postural comfort with the brake pedal at the head-end. During in-room transportation, participants generally reported “Neither Low nor High” physical demands with the 5th wheel activated, compared to “Moderately High” physical demands when the 5th wheel was deactivated. Corridor transportation was similarly reported to be easier when a steering-assistance feature (the 5th wheel or front caster lock) was activated. Conclusions Braking and steering-assistance features of hospital beds can have important effects on task efficiency and physical demands placed on healthcare workers. Selection of specific designs may thus be able to improve productivity and contribute to a reduction in WMSDs risk among healthcare workers.

Altered photic and non-photic phase shifts in 5-HT1A receptor knockout mice

The mammalian circadian clock located in the suprachiasmatic nucleus (SCN) is thought to be modulated by 5-HT. 5-HT is though to inhibit photic phase shifts by inhibiting the release of glutamate from retinal terminals, as well as by decreasing the responsiveness of retinorecipient cells in the SCN. Furthermore, there is also evidence that 5-HT may underlie, in part, non-photic phase shifts of the circadian system. Understanding the mechanism by which 5-HT accomplishes these goals is complicated by the wide variety of 5-HT receptors found in the SCN, the heterogeneous organization of both the circadian clock and the location of 5-HT receptors, and by a lack of sufficiently selective pharmacological agents for the 5-HT receptors of interest. Genetically modified animals engineered to lack a specific 5-HT receptor present an alternative avenue of investigation to understand how 5-HT regulates the circadian system. Here we examine behavioral and molecular responses to both photic and non-photic stimuli in mice lacking the 5-HT1A receptor. When compared with wild-type controls, these mice exhibit larger phase advances to a short late-night light pulse and larger delays to long 12 h light pulses that span the whole subjective night. Fos and mPer1 expression in the retinorecipient SCN is significantly attenuated following late-night light pulses in the 5-HT1A knockout animals. Finally, non-photic phase shifts to (±)-8-hydroxy-2-(dipropylamino)tetralin hydrobromide (8-OH-DPAT) are lost in the knockout animals, while attenuation of the phase shift to the long light pulse due to rebound activity following a wheel lock is unaffected. These findings suggest that the 5-HT1A receptor plays an inhibitory role in behavioral phase shifts, a facilitatory role in light-induced gene expression, a necessary role in phase shifts to 8-OH-DPAT, and is not necessary for activity-induced phase advances that oppose photic phase shifts to long light pulses.

Cessation of daily exercise dramatically alters precursors of hepatic steatosis in Otsuka Long‐Evans Tokushima Fatty (OLETF) rats

The purpose of this study was to delineate potential mechanisms initiating the onset of hepatic steatosis following the cessation of daily physical activity. Four-week-old, hyperphagic/obese Otsuka Long-Evans Tokushima Fatty rats were given access to voluntary running wheels for 16 weeks to prevent the development of hepatic steatosis. The animals were then suddenly transitioned to a sedentary condition as wheels were locked (wheel lock; WL) for 5 h (WL5), 53 h (WL53) or 173 h (WL173). Importantly after the cessation of daily exercise (5-173 h), no changes occurred in body weight, fat pad mass (omental and retroperitoneal), food intake, serum insulin, hepatic triglycerides or in the exercise-suppressed hepatic stearoyl-CoA desaturase-1 and peroxisome proliferator-activated receptor-gamma protein content. However, complete hepatic fatty acid oxidation and mitochondrial enzyme activities were highest at WL5 and WL53 and dropped significantly to SED levels by WL173. In addition, cessation of daily exercise quickly increased the hepatic protein contents of fatty acid synthase and acetyl-coenzyme A carboxylase (ACC), reduced ACC phosphorylation status, and dramatically increased hepatic malonyl-CoA concentration. This study is the first to show that the sudden cessation of daily exercise in a hyperphagic/obese model activates a subgroup of precursors and processes known to initiate hepatic steatosis, including decreased hepatic mitochondrial oxidative capacity, increased hepatic expression of de novo lipogenesis proteins, and increased hepatic malonyl CoA levels; each probably increasing the susceptibility to non-alcoholic fatty liver disease.

An optimised braking force distribution strategy for articulated vehicles

The minimum stopping distance of a vehicle depends upon the maximum deceleration achievable prior to the wheel lock-up. Braking force distribution has an important and serious role in the vehicle stopping distance and its stability. Improvements can be achieved through the use of braking systems whose brake force distribution is made to be variable. Generally, for correct design of a vehicular brake system it is essential that the ideal brake force distribution among the individual axles be known for empty and loaded vehicles. In the case of two-axle vehicles, those relationships are simple and either can be given in terms of the vehicle deceleration or in terms of the rear axle brake force as a function of the front axle brake force. For a tractor semi-trailer, however, the analysis is more complex since the tractor axle loads are functions of the loading as well as the braking force of the trailer. In this paper, a new approach to achieve the braking force distribution strategy will be presented. For this purpose, the mathematical optimisation process has been implemented. This strategy, defined as an innovative braking force distribution strategy, is based on the wheel slips that can improve the vehicle stability under different levels of decelerations.