A study of the ground-attachment process in natural lightning with emphasis on its breakthrough phase.

Synchronized high-speed (124 or 210 kiloframes per second) video images and wideband electromagnetic field records of the attachment process were obtained for 4 negative strokes in natural lightning at the Lightning Observatory in Gainesville, Florida. The majority of imaged upward connecting leaders (UCLs) and upward unconnected leaders, inferred to be mostly initiated from trees, exhibited a pulsating behavior (brightening/fading cycles). UCLs, whose maximum extent ranged from 11 to 25 m, propagated in virgin air at speeds ranging from 1.8 × 105 to 6.0 × 105 m/s with a mean of 3.4 × 105 m/s. Within about 100 m of the ground, the ratio of speeds of the downward negative leader and the corresponding positive UCL was about 3-4 for 2 events and 0.5 for 1 event. The breakthrough phase (final jump) was imaged for 2 events. The initial length of the common streamer zone (CSZ) was estimated to be about 30-40 m. For 2 events, speeds of positive and negative leaders developing toward each other inside the CSZ were found to be between 2.4 × 106 and 3.7 × 106 m/s. For 1 event, opposite polarity leaders were observed to accelerate inside the CSZ. The current at the end of the breakthrough phase, lasting on average 4.7 µs, was estimated to be approximately one-half of the overall current peak. Thus, about one-half of the current peak traditionally attributed to the return-stroke process is actually associated with two leaders extending toward each other to collision inside the CSZ.

Disease spectrum and management of children admitted with acute respiratory infection in Viet Nam.

OBJECTIVE: To assess the acute respiratory infection (ARI) disease spectrum, duration of hospitalisation and outcome in children hospitalised with an ARI in Viet Nam. METHODS: We conducted a retrospective descriptive study of ARI admissions to primary (Hoa Vang District Hospital), secondary (Da Nang Hospital for Women and Children) and tertiary (National Hospital of Paediatrics in Ha Noi) level hospitals in Viet Nam over 12 months (01/09/2015 to 31/08/2016). RESULTS: Acute respiratory infections accounted for 27.9% (37 436/134 061) of all paediatric admissions; nearly half (47.6%) of all children admitted to Hoa Vang District Hospital. Most (64.6%) of children hospitalised with an ARI were <2 years of age. Influenza/pneumonia accounted for 69.4% of admissions; tuberculosis for only 0.3%. Overall 284 (0.8%) children died; most deaths (269/284; 94.7%) occurred at the tertiary referral hospital. The average duration of hospitalisation was 7.6 days (median 7 days). The average direct hospitalisation cost per ARI admission was 157.5 USD in Da Nang Provincial Hospital. In total, 62.6% of admissions were covered by health insurance. CONCLUSION: Acute respiratory infection is a major cause of paediatric hospitalisation in Viet Nam, characterised by prolonged hospitalisation for relatively mild disease. There is huge potential to reduce unnecessary hospital admission and cost.

Initiation and propagation of cloud-to-ground lightning observed with a high-speed video camera.

Complete evolution of a lightning discharge, from its initiation at an altitude of about 4 km to its ground attachment, was optically observed for the first time at the Lightning Observatory in Gainesville, Florida. The discharge developed during the late stage of a cloud flash and was initiated in a decayed branch of the latter. The initial channel section was intermittently illuminated for over 100 ms, until a bidirectionally extending channel (leader) was formed. During the bidirectional leader extension, the negative end exhibited optical and radio-frequency electromagnetic features expected for negative cloud-to-ground strokes developing in virgin air, while the positive end most of the time appeared to be inactive or showed intermittent channel luminosity enhancements. The development of positive end involved an abrupt creation of a 1-km long, relatively straight branch with a streamer corona burst at its far end. This 1-km jump appeared to occur in virgin air at a remarkably high effective speed of the order of 106 m/s. The positive end of the bidirectional leader connected to another bidirectional leader to form a larger bidirectional leader, whose negative end attached to the ground and produced a 36-kA return stroke.

["Idiopathic" white atrophy]. / Atrophie blanche "idiopathique".

INTRODUCTION: Livedoid vasculitis is a clinico-pathological entity which may be idiopathic or secondary to various disorders. The aim of this study was to search for a thrombogenic biological abnormality in patients with apparently idiopathic livedoid vasculitis. PATIENTS AND METHODS: All the patients with histologically confirmed and apparently idiopathic livedoid vasculitis were evaluated. Blood study included search for anticardiolipin, anti-anionic phospholipids and anti-beta 2 glycoprotein 1 antibodies, platelet aggregation and fibrinolytic system tests, cryofibrinogen and homocysteine serum level and factor V Q506 mutation and prothrombin 20210 G/A variant investigation. Clinical data and effects of treatments were reviewed retrospectively. RESULTS: Eleven of the 21 patients with livedoid vasculitis had an apparently idiopathic form. Seven of them (64 p. 100) had a thrombophilic state: antiphospholipid antibodies (n = 3), increased platelet aggregation (n = 1), cryofibrinogen (n = 1), decreased antithrombin III activity (n = 1) and factor V mutation (n = 1). The necrotic lesions were always localized on the lower limbs with a sensitive neuropathy in 2 cases. Complete remission was sometimes obtained with antiaggregant or anticoagulant therapy, but was unrelated to the thrombophilic abnormalities. CONCLUSION: Various thrombophilic abnormalities are frequently observed in livedoid vasculitis which seems to be the clinical expression of a thrombotic process of the microcirculation of the skin and sometimes of the peripheral nerves. The idiopathic feature of numerous cases gives evidence for the lack of our knowledge on thrombosis of the microcirculation.

Effects of Hatha Yoga Practice on the Health-Related Aspects of Physical Fitness.

Ten healthy, untrained volunteers (nine females and one male), ranging in age from 18-27 years, were studied to determine the effects of hatha yoga practice on the health-related aspects of physical fitness, including muscular strength and endurance, flexibility, cardiorespiratory fitness, body composition, and pulmonary function. Subjects were required to attend a minimum of two yoga classes per week for a total of 8 weeks. Each yoga session consisted of 10 minutes of pranayamas (breath-control exercises), 15 minutes of dynamic warm-up exercises, 50 minutes of asanas (yoga postures), and 10 minutes of supine relaxation in savasana (corpse pose). The subjects were evaluated before and after the 8-week training program. Isokinetic muscular strength for elbow extension, elbow flexion, and knee extension increased by 31%, 19%, and 28% (p<0.05), respectively, whereas isometric muscular endurance for knee flexion increased 57% (p<0.01). Ankle flexibility, shoulder elevation, trunk extension, and trunk flexion increased by 13% (p<0.01), 155% (p<0.001), 188% (p<0.001), and 14% (p<0.05), respectively. Absolute and relative maximal oxygen uptake increased by 7% and 6%, respectively (p<0.01). These findings indicate that regular hatha yoga practice can elicit improvements in the health-related aspects of physical fitness. (c)2001 CHF, Inc.

Artificial tear adsorption on soft contact lenses: methods to test surfactant efficacy.

Spoilage is a primary factor in the biocompatibility of soft contact lenses (SCL) within the lacrimal fluid. Tears are a complex mixture of proteins, lipids, natural surfactants and salts. The spoilation process is due to a contribution of all these components and of the nature of SCL materials themselves. The aim of this study was to set up methods to observe and quantify lacrimal deposits and to select efficient surfactants for preventing protein deposits. The present study was performed on PMMA-NVP SCL. The behaviour of SCL in presence of tears was studied by means of an in vitro artificial tear model consisting of the main tears components and quantified by a colorimetric technique (BCA) performed directly on the lenses. The nature of the deposit was observed directly by atomic force microscopy (AFM) in a liquid medium showing the same adsorption trend noticed in the quantitative results and identifying specific adsorption sites. The assessment of surfactant adsorption was performed using Maron's method, as a mean to evaluate the affinity of surfactant to the surface, while the action of selected surfactants on pre-treated SCL was assessed using the BCA method. Promising results were obtained with these two different methods which can be used easily for the pre-selection of surfactants for further cleaning solution formulation studies.

Protein encapsulation within poly(ethylene glycol)-coated nanospheres. II. Controlled release properties.

The development of injectable nanoparticulate "stealth" carriers for protein delivery is a major challenge. The aim of this work was to investigate the possibility of achieving the controlled release of a model protein, human serum albumin (HSA), from poly(ethylene glycol) (PEG)-coated biodegradable nanospheres (mean diameter of about 200 nm) prepared from amphiphilic diblock PEG-poly(lactic acid) (PLA) copolymers. HSA was efficiently incorporated into the nanospheres, reaching loadings as high as 9% (w/w). Results of the in vitro release studies showed that it is possible to control the HSA release by choosing the appropriate nanosphere size, loading, and composition. These results also revealed that, following their release, HSA molecules readsorbed onto the nanospheres surfaces when they were not protected by a PEG coating. We were surprised to observe that in spite of the water uptake of the PLA-PEG nanospheres [11-29% (w/w)], the copolymer did not significantly degrade after a 15-day incubation period. Therefore, we concluded that during this time HSA release from PLA-PEG nanospheres followed a diffusion mechanism where bulk erosion and surface desorption were negligible.

[Orthostatic increase in blood pressure in the elderly (author's transl)]. / L'élévation tensionnelle orthostatique du sujet àgé.

In a systematic study of orthostatic changes in blood pressure involving 200 unselected patients of an old people's home (mean of age: 80 years), an orthostatic fall in blood pressure, which was almost always moderate and with no detectable clinical consequences, was found in only 14% of patients. On the other hand an orthostatic increase in blood pressure, which still persisted 15 minutes after maintaining the upright position was observed in 55% of these cases. The proportion of cases in which an orthostatic increase in blood pressure was found was not essentially different in the 121 patients considered as normotensive in supine position (i.e. 59%) and in the 79 patients initially hypertensive (i.e. 48%). The occurrence of such an orthostatic hypertension in the elderly, particularly in those considered as normotensive, does not appear to have been reported previously, but such disorder is likely to be associated with underlying physiological changes. It may be related to arteriosclerotic changes in the arterial walls which, in connection with the ageing process, cause a decrease in baroreceptor sensitivity. It may also be assumed that marked and persisting orthostatic increase in blood pressure favors or worsens preexisting arterial lesions, particularly in the brain, and that in such cases appropriate adrenoceptor blocking therapy would therefore be justified.