Effects of very high-frequency sound and ultrasound on humans. Part II: A double-blind randomized provocation study of inaudible 20-kHz ultrasound.

Some people have reported symptoms such as nausea, dizziness, and headaches that they attribute to ultrasound (US) emitted by devices in public places. The primary aim of the present study was to investigate whether inaudible US can provoke adverse symptoms compared to a sham presentation, under double-blind conditions. A second aim was to investigate whether the expectation of US being present could provoke adverse symptoms (a nocebo response). The US stimulus was a 20 kHz tone presented continuously for 20 min set to at least 15 dB below the participants' detection threshold, giving a typical sound pressure level (SPL) of 84 dB. No evidence that US provoked symptoms was found, but there was evidence of small nocebo effects. A case study on an individual with high self-reported sensitivity to US gave similar results. The present study did not reproduce the severe symptoms reported previously by some members of the public; this may be due to the SPL or duration of the stimulus, or strength of the nocebo stimulus. These findings cannot be used to predict outcomes from exposures to sounds that are audible to the individual in question, or to sounds with higher SPLs, longer durations, or different frequency content.

Effects of very high-frequency sound and ultrasound on humans. Part I: Adverse symptoms after exposure to audible very-high frequency sound.

Various adverse symptoms resulting from exposure to very high-frequency sound (VHFS) and ultrasound (US) have previously been reported. This study aimed to establish whether these symptoms are experienced under controlled laboratory conditions and are specific to VHFS/US. To do this, participants were exposed to VHFS/US (at frequencies between 13.5 and 20 kHz and sound pressure levels between 82 and 92 dB) and to a 1 kHz reference stimulus, both at 25 dB above their hearing threshold. The VHFS/US and reference stimuli were presented 4 times, each time for 3 min, during which participants performed a sustained attention task, rated their symptom severity, and had their galvanic skin response (GSR) measured to assess their level of anxiety. Prior to exposure, participants were assigned either to a symptomatic or an asymptomatic group, based on their prior history of symptoms that they attributed to VHFS/US. In both groups, overall discomfort ratings were higher in the VHFS/US condition than the reference condition. In the symptomatic group only, difficulty concentrating and annoyance were also rated higher in the VHFS/US than the reference condition. No difference between the two stimulus conditions was seen in performance on the attention task or on average GSRs for either group.

Effect of acute exposure to radiofrequency electromagnetic fields emitted by a mobile phone (GSM 900 MHz) on electrodermal responsiveness in healthy human.

PURPOSE: The present study aimed to determine the effect of acute exposure to electromagnetic fields (EMF) emitted by a mobile phone on electrodermal activity (EDA) in response to an auditory stimulus. MATERIALS AND METHODS: The EDA of 28 young volunteers was recorded following 26 min of exposure to a GSM mobile phone (900 MHz). Palmar sensors enabled repeat recording of 2 min 45 s in the pre-exposure, exposure and post-exposure phases in response to sound stimuli. RESULTS: The latency, amplitude of skin conductance responses (SCRs), integral of skin conductance response and number of SCRs in response to the auditory stimuli were not modified by exposure. Skin conductance and tonic activity decomposition of the recorded signal were significantly different between the two sessions (p < .0001), but the changes could not be attributed to EMF exposure. There was also a tendency toward a fast reduction in the amplitude and number of electrodermal responses after placement of the mobile phone. In response to successive stimuli, there was a significant difference between the first response and subsequent responses for all variables except latency. CONCLUSIONS: Our results showed a decrease in the number of responses and their amplitude as a result of placement of the mobile device and whether it was turned 'on' or 'off', but there were no changes associated with exposure to GSM radiofrequency waves in this group of volunteers.

Seasonal and time-of-day variations in acute non-image forming effects of illuminance level on performance, physiology, and subjective well-being.

This study investigated seasonal and time-of-day dependent moderations in the strength and direction of acute diurnal non-image forming (NIF) effects of illuminance level on performance, physiology, and subjective well-being. Even though there are indications for temporal variations in NIF-responsiveness to bright light, scientific insights into potential moderations by season are scarce. We employed a 2 (Light: 165 versus 1700 lx at the eye level, within) × 2 (Season: autumn/winter versus spring, between) × 2 (Time of day: morning versus afternoon, between) mixed-model design. During each of the two 90-min experimental sessions, participants (autumn/winter: N = 34; spring: N = 39) completed four measurement blocks (incl. one baseline block of 120 lx at the eye level) each consisting of a Psychomotor Vigilance Task (PVT) and a Backwards Digit-Span Task (BDST) including easy trials (4-6 digits) and difficult trials (7-8 digits). Heart rate (HR) and skin conductance level (SCL) were measured continuously. At the end of each lighting condition, subjective sleepiness, vitality, and mood were measured. The results revealed a clear indication for significant Light * Season interaction effects on both subjective sleepiness and vitality, which appeared only during the morning sessions. Participants felt significantly more vital and less sleepy in winter, but not in spring during bright light exposure in the morning. In line with these subjective parameters, participants also showed significantly better PVT performance in the morning in autumn/winter, but not in spring upon bright light exposure. Surprisingly, for difficult working memory performance, the opposite was found, namely worse performance during bright light exposure in winter, but better performance when exposed to bright light in spring. The effects of bright versus regular light exposure on physiology were quite subtle and largely nonsignificant. Overall, it can be concluded that acute illuminance-induced NIF effects on subjective alertness and vitality as well as objectively measured vigilance in the morning are significantly moderated by season. Possibly, these greater illuminance-induced benefits during the morning sessions in autumn/winter compared to spring occurred due to increased responsiveness to bright light exposure as a function of a relatively low prior light dose in autumn/winter.

Effects of Space Weather on Biomedical Parameters during the Solar Activity Cycles 23-24.

The results of long-term (1998-2012) biomedical monitoring of the biotropic effects of space weather are discussed. A drastic change in statistical distribution parameters in the middle of 2005 was revealed that did not conform to usual sinusoidal distribution of the biomedical data reflecting changes in the number of solar spots over a solar activity cycle. The dynamics of space weather of 2001-2012 is analyzed. The authors hypothesize that the actual change in statistical distributions corresponds to the adaptation reaction of the biosphere to nonstandard geophysical characteristics of the 24th solar activity cycle and the probable long-term decrease in solar activity up to 2067.

Effect of infrared-C radiation on skin temperature, electrodermal conductance and pain in hemiparetic stroke patients.

PURPOSE: A novel application of infrared-C (IR-C) radiation (3-1000 µm) on hemiparetic stroke patients was evaluated. Hot compresses (HC) were used on the paretic shoulders of patients in this placebo-controlled trial to investigate the effects of IR-C on skin temperature, electrodermal conductance (EC) and pain relief. MATERIALS AND METHODS: Skin temperature at the center of the middle deltoid (CMD), Quchi (LI11), and the center of the third metacarpal bone on dorsum of hand (COT) of the subjects at Brunnstrom stage 3-5 before and after IR-C HC, were examined. Meanwhile, EC was measured on Hegu (LI4), Quchi and Juanyu (LI15). Pain intensity was evaluated before and after treatment. RESULTS: Skin temperature increased significantly at the CMD and COT on the paretic side in males. In females after treatment, similar skin temperatures were found in each measured region on both the paretic and non-paretic sides. The EC on the paretic side tended to be higher than the non-paretic side before treatment. After treatment, the EC on paretic side declined in both sexes and became even lower than the non-paretic side in females. Pain intensity was lessened after treatment especially in males, which appeared to correspond with an increase in skin temperature and a decrease in EC. CONCLUSION: IR-C hot compress is a promising method for stroke patients in rehabilitation. Physiological mechanisms of this treatment were proposed and summarized from this research.

Beyond extinction: Habituation eliminates conditioned skin conductance across contexts.

A marked signature of fear extinction is its vulnerability for relapse. Here, we departed from the standard extinction principle and examined the ability of habituation to reduce conditioned fear reactions and prevent relapse. In a human fear conditioning paradigm, we first established one visual stimulus as a signal for an impending aversive electrical stimulation, while another visual stimulus was never followed by this stimulation. Next, the screen color changed and participants were exposed to either the visual stimuli without electrical stimulation (extinction treatment) or to the electrical stimulation without the visual stimuli (habituation treatment). Finally, the screen color changed back and the two visual stimuli were tested. Verbal ratings showed a return of conditioned shock-expectancy in the two groups, while skin conductance reactivity showed conditioned discrimination following exposures to the visual stimuli, but not following exposures to the electrical stimulation. We conclude that a habituation treatment outperforms an extinction treatment, and that shock-expectancy and skin conductance can dissociate under some conditions.

The impact of modulated, colored light on the autonomic nervous system.

CONTEXT: Scientists are now finding that light acts on individuals through multiple pathways, most notably the optic nerve that links to the brain's visual cortex, providing a pathway for the visual effects of light. The optic nerve also links to the more recently discovered retinohypothalamic tract, providing a pathway for the nonvisual effects of light. However, specific effects have not yet been widely evaluated clinically, especially in relationship to chromotherapy (ie, therapy based on colored light). OBJECTIVE: The purpose of this study was to evaluate the impact of modulated-light projections, perceived through the eyes, on the autonomic nervous system (ANS). DESIGN: The research team designed a randomized, controlled, partially blinded study with three intervention groups and one control group. SETTING: The study took place in two locations: (1) Midwestern State University, Wichita Falls, Texas, USA (40 participants) and Centre de Santé Satori, Québec, Canada (77 participants). PARTICIPANTS: The research team recruited 117 individuals, 89 women and 28 men, to participate in the study. Participants were normal healthy individuals who were 19 to 72 y old (average age = 43 y). INTERVENTION: Three types of light projections, each containing both specific colors and specific modulations in the frequency range of brainwaves, were tested, in addition to a placebo projection consisting of nonmodulated white light. OUTCOME MEASURES: Evaluation was done using a combination of physiological measures-heart rate (HR), heart rate variability (HRV), and skin conductance (SC)- and psychological tests: the Profile of Mood States (POMS) and a subjective evaluation questionnaire. RESULTS: The research team observed significant differences in the effects of light-modulation projections from baseline to postsession as compared with an equivalent intensity of white light, including decreased HR, increased HRV standard deviations of normalized NN (beat-to-beat) intervals (SDNN), very low (VLF) and low frequency (LF) levels, and decreased POMS total mood disturbance (TMD). Also, the different colors of modulated light were found to result in different ANS effects. CONCLUSIONS: Interest is growing in the therapeutic potential of light. The effects demonstrated in the current study indicate that colored light could significantly enrich the therapeutic potential of light, and further research into chromotherapy is warranted.

The role of skin conductivity in a low frequency exposure assessment for peripheral nerve tissue according to the ICNIRP 2010 guidelines.

Based on numerical computations using commercially available finite difference time domain code and a state-of-the art anatomical model of a 5-year old child, the influence of skin conductivity on the induced electric field strength inside the tissue for homogeneous front-to-back magnetic field exposure and homogeneous vertical electric field exposure was computed. Both ungrounded as well as grounded conditions of the body model were considered. For electric field strengths induced inside CNS tissue the impact of skin conductivity was found to be less than 15%. However, the results demonstrated that the use of skin conductivity values as obtainable from the most widely used data base of dielectric tissue properties and recommended by safety standards are not suitable for exposure assessment with respect to peripheral nerve tissue according to the ICNIRP 2010 guidelines in which the use of the induced electric field strengths inside the skin is suggested as a conservative surrogate for peripheral nerve exposure. This is due to the fact that the skin conductivity values derived from these data bases refer to the stratum corneum, the uppermost layer of the skin, which does not contain any nerve or receptor cells to be protected from stimulation effects. Using these skin conductivity values which are approximately a factor 250-500 lower than skin conductivity values used in studies on which the ICNIRP 2010 guidelines are based on, may lead to overestimations of the induced electric field strengths inside the skin by substantially more than a factor of 10. However, reliable conductivity data of deeper skin layers where nerve and preceptor cells are located is very limited. It is therefore recommended to include appropriate background information in the ICNIRP guidelines and the dielectric tissue property databases, and to put some emphasis on a detailed layer-specific characterization of skin conductivity in near future.

Application of a topical biomimetic electrical signaling technology to photo-aging: a randomized, double-blind, placebo-controlled trial of a galvanic zinc-copper complex.

BACKGROUND: The first signs of facial skin photo-aging often occur in the skin of the periorbital area and include sagging, loss of firmness and definition, and sallowness. Epidermal wounds have been shown to alter the trans-epithelial electrical potential creating an electric signal that directs cell migration in epithelial wound healing; this electric field declines sharply with age. A topical galvanic zinc-copper complex, which couples elemental zinc and copper to create a biomimetic electric field, has demonstrated anti-inflammatory activity and extracellular matrix improvement in vitro, including collagen and elastin production. OBJECTIVES: To evaluate the efficacy and tolerability of a galvanic zinc-copper complex on photo-aging parameters in a randomized, double-blind, placebo-controlled clinical trial. MATERIALS AND METHODS: In this eight-week study, women (40-65 years) with mild to moderate photo-aging were randomized to use placebo or 1 of 3 galvanic zinc-copper complex compositions (gel and activating moisturizer). Efficacy evaluations included clinical grading, specialized clinical imaging, and subject self-assessments performed at baseline, 15-30 minutes after product application and after 1, 2, 4, and 8 weeks. Tolerability was based on adverse events and clinical grading of irritation. Significance was set at P?0.05 versus baseline and between treatment groups. RESULTS: The study was completed by 124 women. Compositions containing the galvanic zinc-copper complex showed statistically significant clinical improvements versus placebo and baseline rapidly (15-30 min) after application and through week 8. Clinical grading showed significant improvement versus placebo in skin radiance and under-eye dark circles 15-30 minutes after first application with continued improvement through week 8, and in overall photo-damage, fine lines, lifted appearance of the eyes, and under-eye wrinkles starting after two weeks and continuing through week 8. Test compositions were well tolerated. CONCLUSION: This galvanic zinc-copper complex provided rapid and lasting improvements versus placebo in photo-aged skin, supporting its use in topical anti-aging formulations.

The remote sensing of mental stress from the electromagnetic reflection coefficient of human skin in the sub-THz range.

Recent work has demonstrated that the reflection coefficient of human skin in the frequency range from 95 to 110 GHz (W band) mirrors the temporal relaxation of stress induced by physical exercise. In this work, we extend these findings to show that in the event of a subtle trigger to stress, such as mental activity, a similar picture of response emerges. Furthermore, the findings are extended to cover not only the W band (75-110 GHz), but also the frequency band from 110 to 170 GHz (D band). We demonstrate that mental stress, induced by the Stroop effect and recorded by the galvanic skin response (GSR), can be correlated to the reflection coefficient in the aforementioned frequency bands. Intriguingly, a light physical stress caused by repeated hand gripping clearly showed an elevated stress level in the GSR signal, but was largely unnoted in the reflection coefficient in the D band. The implication of this observation requires further validation.

Cognitive and physiological responses in humans exposed to a TETRA base station signal in relation to perceived electromagnetic hypersensitivity.

Terrestrial Trunked Radio (TETRA) technology ("Airwave") has led to public concern because of its potential interference with electrical activity in the brain. The present study is the first to examine whether acute exposure to a TETRA base station signal has an impact on cognitive functioning and physiological responses. Participants were exposed to a 420 MHz TETRA signal at a power flux density of 10 mW/m(2) as well as sham (no signal) under double-blind conditions. Fifty-one people who reported a perceived sensitivity to electromagnetic fields as well as 132 controls participated in a double-blind provocation study. Forty-eight sensitive and 132 control participants completed all three sessions. Measures of short-term memory, working memory, and attention were administered while physiological responses (blood volume pulse, heart rate, skin conductance) were monitored. After applying exclusion criteria based on task performance for each aforementioned cognitive measure, data were analyzed for 36, 43, and 48 sensitive participants for these respective tasks and, likewise, 107,125, and 129 controls. We observed no differences in cognitive performance between sham and TETRA exposure in either group; physiological response also did not differ between the exposure conditions. These findings are similar to previous double-blind studies with other mobile phone signals (900-2100 MHz), which could not establish any clear evidence that mobile phone signals affect health or cognitive function.

Do TETRA (Airwave) base station signals have a short-term impact on health and well-being? A randomized double-blind provocation study.

BACKGROUND: "Airwave" is the new communication system currently being rolled out across the United Kingdom for the police and emergency services, based on the Terrestrial Trunked Radio Telecommunications System (TETRA). Some police officers have complained about skin rashes, nausea, headaches, and depression as a consequence of using their Airwave handsets. In addition, a small subgroup in the population self-report being sensitive to electromagnetic fields (EMFs) in general. OBJECTIVES: We conducted a randomized double-blind provocation study to establish whether short-term exposure to a TETRA base station signal has an impact on the health and well-being of individuals with self-reported "electrosensitivity" and of participants who served as controls. METHODS: Fifty-one individuals with self-reported electrosensitivity and 132 age- and sex-matched controls participated in an open provocation test; 48 sensitive and 132 control participants went on to complete double-blind tests in a fully screened semianechoic chamber. Heart rate, skin conductance, and blood pressure readings provided objective indices of short-term physiological response. Visual analog scales and symptom scales provided subjective indices of well-being. RESULTS: We found no differences on any measure between TETRA and sham (no signal) under double-blind conditions for either controls or electrosensitive participants, and neither group could detect the presence of a TETRA signal at rates greater than chance (50%). When conditions were not double blind, however, the self-reported electrosensitive individuals did report feeling worse and experienced more severe symptoms during TETRA compared with sham. CONCLUSIONS: Our findings suggest that the adverse symptoms experienced by electrosensitive individuals are due to the belief of harm from TETRA base stations rather than to the low-level EMF exposure itself.

Specific patterns of weak (1 microTesla) transcerebral complex magnetic fields differentially affect depression, fatigue, and confusion in normal volunteers.

Normal young adults were exposed for 20 min once per week for a total of 3 sessions to 1 of 7 configurations of weak (1 microTesla) magnetic fields or to a sham field. The fields were spatially rotated and applied through the brain at the level of the temporoparietal lobes. The Profile of Mood States was taken before and after each session. Before, during, and after the treatments, heart rate, plethysmographic activity, and skin conductance were measured by computer. The results indicated that the burst-firing pattern previously demonstrated to be effective for clinical depression, improved mood and vigour compared to the sham-field or other treatments. Subjects who were exposed to a burst-firing pattern, a complex-sequenced pattern, and a pattern whose electrical equivalents stimulate long-term potential in hippocampus slices also exhibited less psychometric fatigue after the sessions compared to subjects who received the sham field or random-sequenced fields. These results replicate previous studies and indicate that rationally designed complex patterns of magnetic fields may simulate pharmacological treatments.

A high-voltage bipolar transconductance amplifier for electrotactile stimulation.

This paper describes a high-performance transconductance amplifier specifically designed for electrotactile (electrocutaneous) stimulation. It enables voltages up to +/-600 V to be produced at the output that will allow the psychophysiological performance associated with stimulation of the fingertip using various stimulation waveforms to be studied more thoroughly. The design has a transconductance of up to 20 mA/V, an 8.8-Momega output resistance, and can provide output currents up to +/-20 mA. A complete schematic diagram is presented along with a discussion of theory of operation and safety issues as well as performance and derating plots from the implemented design.

The characteristics of aromatase deficient hairless mice indicate important roles of extragonadal estrogen in the skin.

The roles of extragonadal estrogen in the skin are poorly understood, due to the lack of proper animal models. We examined the skin phenotypes of aromatase-knockout hairless (ArKO) mice and wild-type hairless (WT) mice, both of which were obtained through crossbreeding of Ar+/- mice and hairless mice. Differences in the skins of ArKO and WT mice were compared with those of ovariectomized (OVX) and control (Sham) mice. A difference was observed in the skin tone of ArKO mice, which is pale white and differs from the pinkish tone of all other mice. However, both ArKO and OVX mice similarly exhibited deteriorations of skin properties as compared to their respective controls. Furthermore, all the deteriorations were similarly amplified by chronic UVB irradiation in both ArKO and OVX mice as compared to their respective controls. The unique skin phenotype of ArKO mice was observed in sunburn reactions. Specifically, skins of ArKO mice showed no reaction after an acute UVB irradiation at dose intensities caused sunburn in others. However, follow-up observation found delayed reactions associated with brownish skin color and swelling only in ArKO mice, thereby suggesting that the role of extragonadal estrogen may be connected with the protective reactions of skin.

Neuroticism-Anxiety, Impulsive-Sensation Seeking and autonomic responses to somatosensory stimuli.

This study focused on autonomic responding in participants who scored high vs. low on the Neuroticism-Anxiety (N-Anx) and Impulsive-Sensation Seeking (Imp-SS) dimensions of the Zuckerman-Kuhlman Personality Questionnaire--Form III. Participants were presented with series of tones (standards, deviants and novels) and they received a mild electric shock (one, two or three pulses) at each 15th tone. Resting pre-stimulus skin conductance level (SCL) and heart rate (HR) level was recorded, as well as the skin conductance response (SCR) and (anticipatory) HR response to the electric stimuli. The autonomic measures differentiated between high- vs. low Imp-SS participants but failed to discriminate between high- vs. low N-Anx participants, with the exception that high N-Anx participants showed smaller SCRs on some trials compared to the low N-Anx participants. High Imp-SS had a lower pre-stimulus SCL and smaller SCRs to deviant stimuli compared to low Imp-SS participants. Additionally, their HR acceleration was smaller in anticipation of the first and the deviant tones whereas their deceleratory response was larger relative to the HR changes observed for the low Imp-SS participants. This pattern of findings was taken to suggest that high Imp-SS participants are more arousable and less prone to defensive reactions to novel or aversive stimulation.

Effect of hyperglycemia on electrodermal activity in diabetic rats.

This study investigated the relationship between hyperglycemia and electrodermal activity (EDA) parameters in streptozotocin (STZ) induced diabetic rats. The article evaluates the course of development of neurophysiological alterations in the peripheral nervous system in diabetic rats through EDA. Rats were made diabetic using a moderate dose of STZ (DI) and high dose (DII). The placebo group (P) was injected with physiological saline. EDA was recorded 1 h before the injection (beginning, 0, day), 1st day (one day after the injection) and 10th day. Skin conductance level (SCL) was lower in DII than P on the 1st and the 10th days. The SCL and SC fluctuation rate (SCFr) of DI were significantly lower on the 10th day compared to their first record. SC response rate (SCRr) was lower on the 10th day compared to the 1st day, in the DI. In the DI, SCL, SC fluctuation rate (SCFr) and SC response rate (SCRr) were lower on the 10th day compared to the 1st day. The DII was statistically higher in electrodermal non-responsiveness compared to other groups on the 1st day. The results obtained show that hyperglycemia affects the peripheral nervous system, and EDA parameters are affected by blood glucose level. It is suggested that EDA is a simple and non-invasive electrophysiological method in early diagnosis of diabetic neuropathy.

Effects of RF exposure of teenagers and adults by CDMA cellular phones.

Many cellular phone provocation studies have been conducted since the question of increased health risk from extended usage of cellular phones became a social issue. Internationally, most studies have been conducted regarding the effects of GSM cellular phones on blood pressure and heart rate of adult volunteers. On the other hand, very few provocation studies have been conducted regarding the physiological effects of CDMA phones on teenagers. In this study, two volunteer groups consisting of 21 teenagers and 21 adults were exposed to 300 mW of radio frequency (RF) electromagnetic field emitted by a CDMA cellular phone for half an hour. Physiological parameters such as systolic and diastolic blood pressures, heart rate, respiration rate, and skin resistance were simultaneously measured. All the parameters for both groups were unaffected during the exposure except for decreased skin resistance of the teenager group (P < .0001). For the regrouped 23 male and 19 female subjects, all the parameters for both groups were unaffected during the exposure except for decreased skin resistance of the male subjects (P = .0026). Those resistances at 10 min after the terminated exposure returned to the resistances at rest regardless of the different groups of age and sex.

Effect of electromagnetic fields emitted by cellular phones on the latency of evoked electrodermal activity.

The widespread use of cellular phones raises the question of their possible adverse biological effects, especially on the central nervous system (CNS). Therefore, the authors examined the effect of electromagnetic fields emitted by cellular phones (CPEMFs) on the evoked neuronal activity of CNS relating to generation and representation of electrodermal activity (EDA), an index of sympathetic nervous system activity. EDA (skin resistance response; SRR) latency was lengthened approximately 200 ms with CPEMFs exposure irrespective of the head site next to mobile phone used. Hemispheric asymmetry of EDA-2 pathway, which is represented by shorter SRR latency in the right hand of the right hand responders, was also distorted with CPEMFs. Because the CNS regions including EDA-2 are also involved in tasks of motor timing and time estimation, delayed response in this neuronal network due to CPEMFs exposure may increase the response time of mobile phone users. Therefore, the findings point to the potential risks of mobile phones on the function of CNS and consequently, possible increase in the risk of phone-related driving hazards.