Exercise-induced potentiation of the acute hypoxic ventilatory response: Neural mechanisms and implications for cerebral blood flow.

A given dose of hypoxia causes a greater increase in pulmonary ventilation during physical exercise than during rest, representing an exercise-induced potentiation of the acute hypoxic ventilatory response (HVR). This phenomenon occurs independently from hypoxic blood entering the contracting skeletal muscle circulation or metabolic byproducts leaving skeletal muscles, supporting the contention that neural mechanisms per se can mediate the HVR when humoral mechanisms are not at play. However, multiple neural mechanisms might be interacting intricately. First, we discuss the neural mechanisms involved in the ventilatory response to hypoxic exercise and their potential interactions. Current evidence does not support an interaction between the carotid chemoreflex and central command. In contrast, findings from some studies support synergistic interactions between the carotid chemoreflex and the muscle mechano- and metaboreflexes. Second, we propose hypotheses about potential mechanisms underlying neural interactions, including spatial and temporal summation of afferent signals into the medulla, short-term potentiation and sympathetically induced activation of the carotid chemoreceptors. Lastly, we ponder how exercise-induced potentiation of the HVR results in hyperventilation-induced hypocapnia, which influences cerebral blood flow regulation, with multifaceted potential consequences, including deleterious (increased central fatigue and impaired cognitive performance), inert (unchanged exercise) and beneficial effects (protection against excessive cerebral perfusion).

Smart Artificial Markers for Accurate Visual Mapping and Localization.

Artificial marker mapping is a useful tool for fast camera localization estimation with a certain degree of accuracy in large indoor and outdoor environments. Nonetheless, the level of accuracy can still be enhanced to allow the creation of applications such as the new Visual Odometry and SLAM datasets, low-cost systems for robot detection and tracking, and pose estimation. In this work, we propose to improve the accuracy of map construction using artificial markers (mapping method) and camera localization within this map (localization method) by introducing a new type of artificial marker that we call the smart marker. A smart marker consists of a square fiducial planar marker and a pose measurement system (PMS) unit. With a set of smart markers distributed throughout the environment, the proposed mapping method estimates the markers' poses from a set of calibrated images and orientation/distance measurements gathered from the PMS unit. After this, the proposed localization method can localize a monocular camera with the correct scale, directly benefiting from the improved accuracy of the mapping method. We conducted several experiments to evaluate the accuracy of the proposed methods. The results show that our approach decreases the Relative Positioning Error (RPE) by 85% in the mapping stage and Absolute Trajectory Error (ATE) by 50% for the camera localization stage in comparison with the state-of-the-art methods present in the literature.

Towards the Use of Blockchain in Mobile Health Services and Applications.

With the advent of cryptocurrencies and blockchain, the growth and adaptation of cryptographic features and capabilities were quickly extended to new and underexplored areas, such as healthcare. Currently, blockchain is being implemented mainly as a mechanism to secure Electronic Health Records (EHRs). However, new studies have shown that this technology can be a powerful tool in empowering patients to control their own health data, as well for enabling a fool-proof health data history and establishing medical responsibility. Additionally, with the proliferation of mobile health (m-Health) sustained on service-oriented architectures, the adaptation of blockchain mechanisms into m-Health applications creates the possibility for a more decentralized and available healthcare service. Hence, this paper presents a review of the current security best practices for m-Health and the most used and widely known implementations of the blockchain protocol, including blockchain technologies in m-Health. The main goal of this comprehensive review is to further discuss and elaborate on identified open-issues and potential use cases regarding the uses of blockchain in this area. Finally, the paper presents the major findings, challenges and advantages on future blockchain implementations for m-Health services and applications.

Modulation of spinal cord excitability following remote limb ischemic preconditioning in healthy young men.

Remote limb ischemic preconditioning (RIPC) has shown to improve dynamic postural control in humans. However, studies on the underlying adaptations of spinal cord networks have never been performed. The present work addresses this issue by investigating parameters from the soleus H-reflex recruitment curve (RC), presynaptic mechanisms of reflex modulation (presynaptic inhibition-PSI, and post activation depression-PAD), and the excursion of the center of pressure (CP) recorded during 1 min in upright stance over a compliant surface. A sham ischemic protocol (partial obstruction of blood flow) was applied to the contralateral thigh along four consecutive days. The same procedure was repeated with full obstruction (RIPC) three days after ending the sham protocol. Data were collected before and after both sham and RIPC protocols. The follow-up data were collected five days after the last ischemic intervention. Significant reduction was detected for both the fast oscillations of the CP (higher frequency components) and the parameter estimated from the RC corresponding to the high amplitude H-reflexes (p < 0.05). Even though the magnitude of effects was similar, it was washed out within three days after sham, but persisted for at least five days after RIPC. No significant differences were found for PSI and PAD levels across conditions. These findings indicate that RIPC leads to enduring changes in spinal cord excitability for the latest reflexively recruited motoneurons, along with improvement in balance control. However, these adaptations were not mediated by the presynaptic mechanisms currently assessed.

Carotid chemoreflex activity restrains post-exercise cardiac autonomic control in healthy humans and in patients with pulmonary arterial hypertension.

KEY POINTS: Dysfunction of post-exercise cardiac autonomic control is associated with increased mortality risk in healthy adults and in patients with cardiorespiratory diseases. The afferent mechanisms that regulate the post-exercise cardiac autonomic control remain unclear. We found that afferent signals from carotid chemoreceptors restrain the post-exercise cardiac autonomic control in healthy adults and patients with pulmonary arterial hypertension (PAH). Patients with PAH had higher carotid chemoreflex sensitivity, and the magnitude of carotid chemoreceptor restraint of autonomic control was greater in patients with PAH as compared to healthy adults. The results demonstrate that the carotid chemoreceptors contribute to the regulation of post-exercise cardiac autonomic control, and suggest that the carotid chemoreceptors may be a potential target to treat post-exercise cardiac autonomic dysfunction in patients with PAH. ABSTRACT: Dysfunction of post-exercise cardiac autonomic control predicts mortality, but its underlying mechanisms remain unclear. We tested whether carotid chemoreflex activity restrains post-exercise cardiac autonomic control in healthy adults (HA), and whether such restraint is greater in patients with pulmonary arterial hypertension (PAH) who may have both altered carotid chemoreflex and altered post-exercise cardiac autonomic control. Twenty non-hypoxaemic patients with PAH and 13 age- and sex-matched HA pedalled until 90% of peak work rate observed in a symptom-limited ramp-incremental exercise test. Recovery consisted of unloaded pedalling for 5 min followed by seated rest for 6 min. During recovery, subjects randomly inhaled either 100% O2 (hyperoxia) to inhibit the carotid chemoreceptor activity, or 21% O2 (normoxia) as control. Post-exercise cardiac autonomic control was examined via heart rate (HR) recovery (HRR; HR change after 30, 60, 120 and 300 s of recovery, using linear and non-linear regressions of HR decay) and HR variability (HRV; time and spectral domain analyses). As expected, the PAH group had higher carotid chemosensitivity and worse post-exercise HRR and HRV than HA. Hyperoxia increased HRR at 30, 60 and 120 s and absolute spectral power HRV in both groups. Additionally, hyperoxia resulted in an accelerated linear HR decay and increased time domain HRV during active recovery only in the PAH group. In conclusion, the carotid chemoreceptors restrained recovery of cardiac autonomic control from exercise in HA and in patients with PAH, with the restraint greater for some autonomic indexes in patients with PAH.

Verrucoconiothyrium ambiguum sp. nov., a novel species isolated from sea water, and affiliation of the genus Verrucoconiothyrium to the family Didymellaceae.

The genus Verrucoconiothyrium was erected to accommodate Coniothyrium-like species with verruculose conidia. So far, it includes only four species, which have been found in association with plants, and very little is known about their distribution and host preferences. In this study, a Coniothyrium-like fungus isolated from sea water from the north of Portugal was characterised. Phylogenetic analysis, based on sequence data of the internal transcribed spacer and beta-tubulin loci, placed this fungus within the genus Verrucoconiothyrium but clearly distinct from the other known species. A novel species Verrucoconiothyrium ambiguumsp. nov. is described and illustrated. The taxonomic affiliation of the genus Verrucoconiothyrium at the family level was addressed through individual and combined gene genealogies. Our results show that the genus Verrucoconiothyrium is a member of the family Didymellaceae.

Biodiversity of Penicillium species from marine environments in Portugal and description of Penicillium lusitanum sp. nov., a novel species isolated from sea water.

During an extensive survey of marine fungi in coastal marine environments from Portugal, a collection of Penicillium isolates were obtained from sea water, macroalgae and driftwood. Sixteen distinct Penicillium species were identified with Penicillium terrigenum and Penicillium brevicompactum being the most frequent. A Penicillium species isolated from sea water could not be affiliated to any known species. Phylogenetic analyses based on the ITS region of the rDNA and the beta-tubulin (benA) gene placed it into Penicillium section Ramosa, distinct from all currently known species and with Penicillium tunisiense as its closest relative. Although having similar morphological characteristics, these species differ in micromorphological and molecular characters. Thus, Penicillium lusitanum sp. nov. is proposed as a novel species.

Water drinking enhances the gain of arterial baroreflex control of muscle sympathetic nerve activity in healthy young humans.

NEW FINDINGS: What is the central question of this study? Water drinking increases muscle sympathetic nerve activity (MSNA), and it increases arterial blood pressure (ABP) in older populations but not in young healthy subjects. Does an increase in gain of arterial baroreflex control of MSNA contribute to maintenance of ABP after water drinking in healthy young subjects? What is the main finding and its importance? The gain of arterial baroreflex control of MSNA was increased and remained elevated 60 min after water drinking (500 ml) but remained unchanged after saline intake. An enhancement in gain of arterial baroreflex control of MSNA contributes to the maintenance of ABP after water drinking in young healthy subjects, probably via osmosensitive mechanisms. ABSTRACT: Water drinking increases muscle sympathetic nerve activity (MSNA), which is accompanied by a profound pressor response in patients with impaired arterial baroreflex function and in older populations, but not in healthy young subjects. We tested the hypothesis that an enhancement in the gain of arterial baroreflex control of MSNA contributes to the maintenance of arterial blood pressure after water drinking in healthy young subjects. The MSNA, arterial blood pressure and heart rate were measured in 10 healthy men (24 ± 2 years old; mean ± SD) before and for 60 min after ingestion of 500 ml of bottled water or saline solution. Weighted linear regression analysis between MSNA and diastolic blood pressure was used to determine the gain (i.e. sensitivity) of arterial baroreflex control of MSNA. After water drinking, MSNA was significantly elevated within 15 min and remained above baseline for up to 60 min [e.g. 21 ± 10 bursts (100 heart beats)-1  mmHg-1 at baseline versus 35 ± 14 bursts (100 heart beats)-1  mmHg-1 at 30 min; P < 0.01], whereas mean arterial blood pressure (e.g. 87 ± 7 mmHg at baseline versus 89 ± 7 mmHg at 30 min; P = 0.34) and heart rate were unchanged. The arterial baroreflex-MSNA gain for bursts incidence was increased and remained elevated throughout the protocol [e.g. -2.25 ± 0.99 bursts (100 heart beats)-1  mmHg-1 at baseline versus -4.32 ± 1.53 bursts (100 heart beats)-1  mmHg-1 at 30 min; P < 0.01]. Importantly, saline intake had no effect on arterial baroreflex-MSNA gain or any neurocardiovascular variables. These findings demonstrate that water drinking enhances the gain of arterial baroreflex control of MSNA in healthy young men, which may contribute to buffering the pressor response after water drinking, probably via osmosensitive mechanisms.

A Versatile Method for Depth Data Error Estimation in RGB-D Sensors.

We propose a versatile method for estimating the RMS error of depth data provided by generic 3D sensors with the capability of generating RGB and depth (D) data of the scene, i.e., the ones based on techniques such as structured light, time of flight and stereo. A common checkerboard is used, the corners are detected and two point clouds are created, one with the real coordinates of the pattern corners and one with the corner coordinates given by the device. After a registration of these two clouds, the RMS error is computed. Then, using curve fittings methods, an equation is obtained that generalizes the RMS error as a function of the distance between the sensor and the checkerboard pattern. The depth errors estimated by our method are compared to those estimated by state-of-the-art approaches, validating its accuracy and utility. This method can be used to rapidly estimate the quality of RGB-D sensors, facilitating robotics applications as SLAM and object recognition.

Effect of Intermittent Hypoxic Training Followed by Intermittent Hypoxic Exposure on Aerobic Capacity of Long Distance Runners.

Effects of intermittent hypoxic training (IHT) are still controversial and detraining effects remain uninvestigated. Therefore, we investigated (a) whether IHT improves aerobic capacity; (b) whether aerobic detraining occurs post-IHT; and (c) whether intermittent hypoxic exposure (IHE) at rest reduces a possible aerobic detraining post-IHT. Twenty eight runners (21 men/7 women; 36 ± 2 years; maximal oxygen uptake [V[Combining Dot Above]O2max] 55.4 ± 1.3 ml·kg·min) participated in a single-blinded placebo-controlled trial. Twice a week, 1 group performed 6 weeks of IHT (n = 11), followed by 4 weeks of IHE (n = 11) at rest (IHT+IHE group). Another group performed 6 weeks of IHT (n = 10), followed by 4 weeks of normoxic exposure (NE, n = 9) at rest (IHT+NE group). A control group performed 6 weeks of normoxic training (NT, n = 7), followed by 4 weeks of NE (n = 6) at rest (NT+NE group). Hematological and submaximal/maximal aerobic measurements were conducted in normoxia at pretraining, posttraining, and postexposure. Hemoglobin concentration did not change, but lactate threshold and running economy improved in all groups at posttraining (p ≤ 0.05 vs. pretraining). Ventilatory threshold, respiratory compensation point, and V[Combining Dot Above]O2max increased after IHT (IHT+IHE group: 7.3, 5.4, and 9.2%, respectively; IHT+NE group: 10.7, 7.5, and 4.8%; p ≤ 0.05 vs. pretraining), but not after NT (-1.1, -1.0, and -3.8%; p > 0.05 vs. pretraining). Such IHT-induced adaptations were maintained at postexposure (p > 0.05 vs. postexposure). In conclusion, IHT induced further aerobic improvements than NT. These additional IHT adaptations were maintained for 4 weeks post-IHT, regardless of IHE.

Mobile-health: A review of current state in 2015.

Health telematics is a growing up issue that is becoming a major improvement on patient lives, especially in elderly, disabled, and chronically ill. In recent years, information and communication technologies improvements, along with mobile Internet, offering anywhere and anytime connectivity, play a key role on modern healthcare solutions. In this context, mobile health (m-Health) delivers healthcare services, overcoming geographical, temporal, and even organizational barriers. M-Health solutions address emerging problems on health services, including, the increasing number of chronic diseases related to lifestyle, high costs of existing national health services, the need to empower patients and families to self-care and handle their own healthcare, and the need to provide direct access to health services, regardless of time and place. Then, this paper presents a comprehensive review of the state of the art on m-Health services and applications. It surveys the most significant research work and presents a deep analysis of the top and novel m-Health services and applications proposed by industry. A discussion considering the European Union and United States approaches addressing the m-Health paradigm and directives already published is also considered. Open and challenging issues on emerging m-Health solutions are proposed for further works.

Integration of Wearable Solutions in AAL Environments with Mobility Support.

The overall demographic profile of current societies point to a significant growth of the elderly people. Associated with the increase of the average hope of life and consequent increase in chronic diseases, there is the need for protection and daily care. Increasing investments in technology, such as Ambient Assisted Living (AAL) solutions, promote the quality of live extending the time people can live in their desired environment. This paper proposes the design, deployment, and real testbed of an e-health wearable monitoring system based on the integration of several AAL tools and platforms for elderly's bio-signals monitoring. This solution includes electrocardiography (ECG), respiration rate, beats per minute, body temperature, and falls detention and notification. The paper also describes, in detail, the real pilot and analyzes some early results concerning the users quality of experience, and the found results are very promising.

Aerobic exercise acutely prevents the endothelial dysfunction induced by mental stress among subjects with metabolic syndrome: the role of shear rate.

Mental stress induces transient endothelial dysfunction, which is an important finding for subjects at cardiometabolic risk. Thus, we tested whether aerobic exercise prevents this dysfunction among subjects with metabolic syndrome (MetS) and whether an increase in shear rate during exercise plays a role in this phenomenon. Subjects with MetS participated in two protocols. In protocol 1 (n = 16), endothelial function was assessed using brachial artery flow-mediated dilation (FMD). Subjects then underwent a mental stress test followed by either 40 min of leg cycling or rest across two randomized sessions. FMD was assessed again at 30 and 60 min after exercise or rest, with a second mental stress test in between. Mental stress reduced FMD at 30 and 60 min after the rest session (baseline: 7.7 ± 0.4%, 30 min: 5.4 ± 0.5%, and 60 min: 3.9 ± 0.5%, P < 0.05 vs. baseline), whereas exercise prevented this reduction (baseline: 7.5 ± 0.4%, 30 min: 7.2 ± 0.7%, and 60 min: 8.7 ± 0.8%, P > 0.05 vs. baseline). Protocol 2 (n = 5) was similar to protocol 1 except that the first period of mental stress was followed by either exercise in which the brachial artery shear rate was attenuated via forearm cuff inflation or exercise without a cuff. Noncuffed exercise prevented the reduction in FMD (baseline: 7.5 ± 0.7%, 30 min: 7.0 ± 0.7%, and 60 min: 8.7 ± 0.8%, P > 0.05 vs. baseline), whereas cuffed exercise failed to prevent this reduction (baseline: 7.5 ± 0.6%, 30 min: 5.4 ± 0.8%, and 60 min: 4.1 ± 0.9%, P < 0.05 vs. baseline). In conclusion, exercise prevented mental stress-induced endothelial dysfunction among subjects with MetS, and an increase in shear rate during exercise mediated this effect.

Sildenafil improves skeletal muscle oxygenation during exercise in men with intermittent claudication.

Endothelial dysfunction caused by defective nitric oxide (NO) signaling plays a pivotal role in the pathogenesis of intermittent claudication (IC). In the present study, we evaluated the acute effects of sildenafil, a phosphodiesterase type 5 inhibitor that acts by prolonging NO-mediated cGMP signaling in vascular smooth muscle, on blood pressure (BP), skeletal muscle oxygenation, and walking tolerance in patients with IC. A randomized, double-blind, crossover study was conducted in which 12 men with stable IC received two consecutive doses of 50 mg of sildenafil or matching placebo and underwent a symptom-limited exercise test on the treadmill. Changes in gastrocnemius deoxy-hemoglobin by near-infrared spectroscopy estimated peripheral muscle O2 delivery-to-utilization matching. Systolic BP was significantly lower during the sildenafil trial relative to placebo during supine rest (∼15 mmHg), submaximal exercise (∼14 mmHg), and throughout recovery (∼18 mmHg) (P < 0.05). Diastolic BP was also lower after sildenafil during upright rest (∼6 mmHg) and during recovery from exercise (∼7 mmHg) (P < 0.05). Gastrocnemius deoxygenation was consistently reduced during submaximal exercise (∼41%) and at peak exercise (∼34%) following sildenafil compared with placebo (P < 0.05). However, pain-free walking time (placebo: 335 ± 42 s vs. sildenafil: 294 ± 35 s) and maximal walking time (placebo: 701 ± 58 s vs. sildenafil: 716 ± 62 s) did not differ between trials. Acute administration of sildenafil lowers BP and improves skeletal muscle oxygenation during exercise but does not enhance walking tolerance in patients with IC. Whether the beneficial effects of sildenafil on muscle oxygenation can be sustained over time and translated into positive clinical outcomes deserve further consideration in this patient population.

Spatial memory: behavioral determinants of persistence in the watermaze delayed matching-to-place task.

The watermaze delayed matching-to-place (DMP) task was modified to include probe trials, to quantify search preference for the correct place. Using a zone analysis of search preference, a gradual decay of one-trial memory in rats was observed over 24 h with weak memory consistently detected at a retention interval of 6 h, but unreliably at 24 h. This forgetting function in the watermaze was similar to that found using a search-preference measure in a food-reinforced dry-land DMP task in a previous study. In a search for strong and weak encoding conditions, essential for a later behavioral tagging study, three encoding trials gave strong 6-h and 24-h memory when trials were separated by 10 min (spaced training) but not 15 sec (massed training). The use of six encoding trials gave good 6-h memory with both spaced and massed training. With respect to weak encoding, placement on the escape platform, instead of the rat swimming to it, resulted in detectable memory at 30 min but this had faded to chance within 24 h. In contrast to the search-preference measure, latencies to cross the correct place revealed neither the gradual forgetting of place memory nor the benefit of spaced training.

Altered locomotor muscle metaboreflex control of ventilation in patients with COPD.

We investigated the locomotor muscle metaboreflex control of ventilation, circulation, and dyspnea in patients with chronic obstructive pulmonary disease (COPD). Ten patients [forced expiratory volume in 1 second (FEV1; means ± SD) = 43 ± 17% predicted] and nine age- and sex-matched controls underwent 1) cycling exercise followed by postexercise circulatory occlusion (PECO) to activate the metaboreflex or free circulatory flow to inactivate it, 2) cold pressor test to interpret whether any altered reflex response was specific to the metaboreflex arc, and 3) muscle biopsy to explore the metaboreflex arc afferent side. We measured airflow, dyspnea, heart rate, arterial pressure, muscle blood flow, and vascular conductance during reflexes activation. In addition, we measured fiber types, glutathione redox balance, and metaboreceptor-related mRNAs in the vastus lateralis. Metaboreflex activation increased ventilation versus free flow in patients (∼15%, P < 0.020) but not in controls (P > 0.450). In contrast, metaboreflex activation did not change dyspnea in patients (P = 1.000) but increased it in controls (∼100%, P < 0.001). Other metaboreflex-induced responses were similar between groups. Cold receptor activation increased ventilation similarly in both groups (P = 0.46). Patients had greater type II skeletal myocyte percentage (14%, P = 0.010), lower glutathione ratio (-34%, P = 0.015), and lower nerve growth factor (NGF) mRNA expression (-60%, P = 0.031) than controls. Therefore, COPD altered the locomotor muscle metaboreflex control of ventilation. It increased type II myocyte percentage and elicited redox imbalance, potentially producing more muscle metaboreceptor stimuli. Moreover, it decreased NGF expression, suggesting a downregulation of metabolically sensitive muscle afferents.NEW & NOTEWORTHY This study's integrative physiology approach provides evidence for a specific alteration in locomotor muscle metaboreflex control of ventilation in patients with COPD. Furthermore, molecular analyses of a skeletal muscle biopsy suggest that the amount of muscle metaboreceptor stimuli derived from type II skeletal myocytes and redox imbalance overcame a downregulation of metabolically sensitive muscle afferents.

Roles of nitric oxide and prostaglandins in the hyperemic response to a maximal metabolic stimulus: redundancy prevails.

Vasodilatory mechanisms controlling post-exercise or post-ischemic hyperemia are thought to be under redundant control and remain incompletely understood. A maximal metabolic stimulus evoked by ischemic exercise (IE) might limit redundancy by full activation of multiple pathways. We tested whether nitric oxide (NO) and/or prostaglandins contribute to the hyperemic response to IE. 17 subjects were randomized into two groups and performed three trials of IE during control (saline), N (G)-monomethyl-L-arginine (L-NMMA; NOS inhibition) (protocol 1) or ketorolac (cyclooxygenase inhibition) infusion (protocol 2), and combined L-NMMA/ketorolac infusion via a brachial arterial catheter. Forearm blood flow (FBF) was measured with venous occlusion plethysmography following IE trials consisting of 5 min of ischemia and simultaneous rhythmic handgrip exercise (final 2 min). Peak and total (area under the curve) FBF and blood pressure (MAP) were measured for 3 min after each trial. Forearm vascular conductance (FVC) was calculated as FBF/MAP. Change (Δ) in peak FBF and FVC from baseline differed only between peak FBF for the saline and L-NMMA + ketorolac trials in protocol 1. Peak ΔFBF was 26.8 ± 2.5, 30.0 ± 2.8, and 33.9 ± 3.6 ml 100 ml(-1) min(-1) for saline, L-NMMA, and L-NMMA + ketorolac trials (P = 0.04). For protocol 1 (n = 8), total ΔFVC was 59.6 ± 4.3, 57.8 ± 6.0, and 59.9 ± 5.6 ml 100 ml(-1) 100 mmHg(-1) for saline, L-NMMA, and L-NMMA + ketorolac trials, (P = 0.82). For protocol 2 (n = 9), total ΔFVC was 54.2 ± 5.0, 56.9 ± 4.5, and 56.5 ± 5.3 ml 100 ml(-1) 100 mmHg(-1) for saline, ketorolac, and ketorolac + L-NMMA trials, (P = 0.69). These results suggest that NO and PGs are not obligatory for the hyperemic response to IE, and other vasodilator mechanisms predominate.

A data encryption solution for mobile health apps in cooperation environments.

BACKGROUND: Mobile Health (mHealth) proposes health care delivering anytime and anywhere. It aims to answer several emerging problems in health services, including the increasing number of chronic diseases, high costs on national health services, and the need to provide direct access to health services, regardless of time and place. mHealth systems include the use of mobile devices and apps that interact with patients and caretakers. However, mobile devices present several constraints, such as processor, energy, and storage resource limitations. The constant mobility and often-required Internet connectivity also exposes and compromises the privacy and confidentiality of health information. OBJECTIVE: This paper presents a proposal, construction, performance evaluation, and validation of a data encryption solution for mobile health apps (DE4MHA), considering a novel and early-proposed cooperation strategy. The goal was to present a robust solution based on encryption algorithms that guarantee the best confidentiality, integrity, and authenticity of users health information. In this paper, we presented, explained, evaluated the performance, and discussed the cooperation mechanisms and the proposed encryption solution for mHealth apps. METHODS: First, we designed and deployed the DE4MHA. Then two studies were performed: (1) study and comparison of symmetric and asymmetric encryption/decryption algorithms in an mHealth app under a cooperation environment, and (2) performance evaluation of the DE4MHA. Its performance was evaluated through a prototype using an mHealth app for obesity prevention and cares, called SapoFit. We then conducted an evaluation study of the mHealth app with cooperation mechanisms and the DE4MHA using real users and a real cooperation scenario. In 5 days, 5 different groups of 7 students selected randomly agreed to use and experiment the SapoFit app using the 7 devices available for trials. RESULTS: There were 35 users of SapoFit that participated in this study. The performance evaluation of the app was done using 7 real mobile devices in 5 different days. The results showed that confidentiality and protection of the users' health information was guaranteed and SapoFit users were able to use the mHealth app with satisfactory quality. Results also showed that the app with the DE4MHA presented nearly the same results as the app without the DE4MHA. The performance evaluation results considered the probability that a request was successfully answered as a function of the number of uncooperative nodes in the network. The service delivery probability decreased with the increase of uncooperative mobile nodes. Using DE4MHA, it was observed that performance presented a slightly worse result. The service average was also slightly worse but practically insignificantly different than with DE4MHA, being considered negligible. CONCLUSIONS: This paper proposed a data encryption solution for mobile health apps, called DE4MHA. The data encryption algorithm DE4MHA with cooperation mechanisms in mobile health allow users to safely obtain health information with the data being carried securely. These security mechanisms did not deteriorate the overall network performance and the app, maintaining similar performance levels as without the encryption. More importantly, it offers a robust and reliable increase of privacy, confidentiality, integrity, and authenticity of their health information. Although it was experimented on a specific mHealth app, SapoFit, both DE4MHA and the cooperation strategy can be deployed in other mHealth apps.

Prediction of gas production rate from shale gas reservoirs using a micro-macro analysis.

Shale gas has become one of the important contributors to the global energy supply. The declining pattern of the gas production rate with time from an unconventional gas reservoir is due to the depletion of shale gas stored in the nanovoids of the shale formation. However, there are only limited ways to predict the variation of the gas production rate with time from an unconventional gas reservoir. This is due to the multiple transport mechanisms of gas in nano-scale pores and changes in shale gas permeability with pressures in nano-scale pores, which is impacted by the pore structure of the shale. In this study, the permeability-pressure (K-p) relationship for different shales (Eagle Ford, Haynesville, Longmaxi and Opalinus) were determined using an equivalent anisotropic pore network model (PNM). This PNM has REV-scale shale gas flow in randomly generated nanovoids and their connection in the shale matrix, and the multiphase flow of shale gas including viscous flow, slip flow and Knudsen diffusion. These predicted K-p correlations were then used in a finite element model (FEM) to predict the variation of the gas production rate with time (flux-time curves) at the macroscale. The simulation results show that the flux-time curves can be simplified to two linear segments in logarithmic coordinates, which are influenced by the fracture length and initial gas pressure. The predicted results using the PNM-FEM were validated by comparing them with the reported field test data. The method described in this study can be used to upscale the gas transport process from micro- to macroscale, which can provide a predictive tool for the gas production in shales.