Littérature scientifique sur le sujet « Head out immersion »

1. Prostaglandins may play a role in the natriuresis seen after acute circulatory challenges. To assess this role in head-out water immersion, we compared, in clearance studies, the effects of acute (24 h) and chronic (7 days) administration of indomethacin, an inhibitor of prostaglandin synthesis, on the renal response to head-out water immersion in six healthy subjects on a 200 mmol of sodium/day diet and on a 40 mmol of sodium/day diet. 2. Indomethacin caused a similar degree of sodium retention on each of these two diets. 3. During the 40 mmol of sodium/day diet, acute administration of indomethacin decreased sodium excretion before, as well as during, head-out water immersion; however, the relative increase caused by head-out water immersion was normal. After chronic administration of indomethacin, both baseline sodium excretion and the natriuresis induced by head-out water immersion were similar to those in control studies. 4. During the 200 mmol of sodium/day diet, indomethacin had no effect on baseline sodium excretion, nor on the natriuretic effect of head-out water immersion. 5. Head-out water immersion decreased tubular lithium reabsorption and increased diluting segment delivery. Despite opposite effects of indomethacin on these parameters, indomethacin did not prevent the tubular effects of head-out water immersion on either diet. However, indomethacin did prevent the marked increase in estimated renal plasma flow and the fall in filtration fraction that were observed during head-out water immersion in the absence of indomethacin (control). 6. Head-out water immersion was not associated with an increase in urinary excretion of prostaglandins. Indomethacin lowered baseline urinary excretion of prostaglandins, which did not change further during head-out water immersion. 7. We therefore conclude that renal prostaglandins are not essential for a normal natriuretic response to head-out water immersion, although they may mediate the vasodilatation induced by head-out water immersion.

1. Recently implanted kidneys may have decreased flexibility to adjust sodium excretion to volume challenges, since modulation by renal sympathetic nerve activity is absent. To examine this hypothesis, we studied the natriuretic response to head-out water immersion in eight patients with well-functioning renal allografts of 37 days (range 24–56 days), at a time when renal re-innervation has probably not occurred. 2. By the third hour of head-out water immersion, sodium excretion had increased equally in the patients (from 120 +21 to 204 +37 μmol/min) and in eight healthy control subjects (from 105 +9 to 191+19 μmol/min). 3. Glomerular filtration rate was 60 + 6 ml/min in the patients and 113 +6 ml/min in the control subjects, and did not change upon head-out water immersion. Estimated renal plasma flow increased upon head-out water immersion in the control group but not in the patients. Blood pressure decreased similarly in both groups. The renal vascular resistance, calculated from these data, decreased in response to head-out water immersion in the control subjects but not in the renal transplant patients. 4. Head-out water immersion suppressed plasma renin activity only in the normal group, whereas the plasma aldosterone level was suppressed in both groups. The natriuretic response in patients was associated with about 3-fold elevated plasma levels of atrial natriuretic peptide. 5. Since renal re-innervation at 37 days after transplantation is very unlikely, these data suggest that inact renal innervation is not mandatory for a normal natriuretic response to head-out water immersion in humans. However, sympathetic modulation might be involved in the decrease in renal vascular resistance and plasma renin activity normally observed during immersion.

Head-out water immersion is known to increase cardiac filling pressure and volume in humans at rest. The purpose of the present study was to assess whether these alterations persist during dynamic exercise. Ten men performed upright cycling exercise on land and in water to the suprasternal notch at work loads corresponding to 40, 60, 80, and 100% maximal O2 consumption (VO2max). A Swan-Ganz catheter was used to measure right atrial pressure (PAP), pulmonary arterial pressure (PAP), and cardiac index (CI). Left ventricular end-diastolic (LVED) and end-systolic (LVES) volume indexes were assessed with echocardiography. VO2max did not differ between land and water. RAP, PAP, CI, stroke index, and LVED and LVES volume indexes were significantly greater (P less than 0.05) during exercise in water than on land. Stroke index did not change significantly from rest to exercise in water but increased (P less than 0.05) on land. Arterial systolic blood pressure did not differ between land and water at rest or during exercise. Heart rates were significantly lower (P less than 0.05) in water only during the two highest work intensities. The results indicate that indexes of cardiac preload are greater during exercise in water than on land.

Personal floatation devices maintain either a semirecumbent flotation posture with the head and upper chest out of the water or a horizontal flotation posture with the dorsal head and whole body immersed. The contribution of dorsal head and upper chest immersion to core cooling in cold water was isolated when the confounding effect of shivering heat production was inhibited with meperidine (Demerol, 2.5 mg/kg). Six male volunteers were immersed four times for up to 60 min, or until esophageal temperature = 34°C. An insulated hoodless dry suit or two different personal floatation devices were used to create four conditions: 1) body insulated, head out; 2) body insulated, dorsal head immersed; 3) body exposed, head (and upper chest) out; and 4) body exposed, dorsal head (and upper chest) immersed. When the body was insulated, dorsal head immersion did not affect core cooling rate (1.1°C/h) compared with head-out conditions (0.7°C/h). When the body was exposed, however, the rate of core cooling increased by 40% from 3.6°C/h with the head out to 5.0°C/h with the dorsal head and upper chest immersed ( P < 0.01). Heat loss from the dorsal head and upper chest was approximately proportional to the extra surface area that was immersed (∼10%). The exaggerated core cooling during dorsal head immersion (40% increase) may result from the extra heat loss affecting a smaller thermal core due to intense thermal stimulation of the body and head and resultant peripheral vasoconstriction. Dorsal head and upper chest immersion in cold water increases the rate of core cooling and decreases potential survival time.

The present investigation was undertaken to test the hypothesis that a circadian variation in the atrial natriuretic factor (ANF) response is responsible for the nocturnal inhibition of renal responses to head-out immersion (HOI). Plasma ANF responses to a 3-h HOI (water temperature 34.5 +/- 0.5 degrees C) were studied during day (1000-1300) and night (2400-0300) in six hydropenic male human subjects. In agreement with the previous observations, the renal responses, especially the diuresis, to HOI were attenuated at night compared with the day; furthermore, plasma renin activity decreased to the same low level during HOI at both day and night. Plasma ANF during time control periods was 30-40 pg/ml without showing any circadian variation. Moreover, plasma ANF showed a similar twofold increase within 1 h of HOI and was maintained at this elevated level throughout the 3-h HOI period in both the daytime and the nighttime series. On termination of HOI, plasma ANF decreased linearly to the pre-HOI level within 1 h. Hematocrit during time control periods was higher during the day compared with the night (P less than 0.05). Although HOI appears to induce a transient increase in plasma volume (as indicated by decreases in hematocrit) during the 1 h of HOI, the magnitude of the decrease in the latter parameters was not different between day and night. It is concluded that nocturnal inhibition of renal responses to HOI cannot be fully accounted for by circadian differences in the ANF and fluid shift response to HOI.

Cardiorenal-endocrine responses to 3-h head-out immersion (HOI) (water temperature = 34.5 +/- 0.5 degrees C) were studied during day (0900–1400 h) and night (2300–0400 h) in six hydropenic male human subjects. Although HOI induced a reversible increase in urine flow in all subjects, the response was faster and greater in magnitude during the day compared with night (P less than 0.05). Na excretion and osmolal clearance (Cosm) also followed the identical response pattern as urine flow, and in fact, the HOI-induced diuresis was entirely accounted for by the increased Cosm. Endogenous creatinine clearance was not different between the day and the night and remained unchanged during HOI. Both plasma renin activity and aldosterone concentration and urinary aldosterone excretion were nearly twofold greater during the day compared with night before HOI but decreased to the same level during HOI in both daytime and the nighttime series (P less than 0.05). There was no correlation between the Na excretion rate and renin-aldosterone levels either before or during HOI. Plasma antidiuretic hormone (ADH) level was comparable between day and night before HOI and decreased to a similar level during HOI in both daytime and nighttime series (P less than 0.05 for nighttime HOI). Cardiac output increased from 3.3 1/min before HOI to 5–6 1/min during HOI without showing any significant circadian difference. Hematocrit, hemoglobin, and plasma concentrations remained unchanged under all conditions. It is concluded that the renal response to HOI is subject to nocturnal inhibition, which cannot be attributed to circadian differences in the degree of HOI-induced central blood pooling, renin-aldosterone, or ADH responses.

Immersion in thermoneutral water increases cardiac output and peripheral blood flow and reduces systemic vascular resistance. This study examined the effects of head-out water immersion on vascular function. Twelve healthy middle-aged males were immersed during 60 min in the seated position, with water at the level of xiphoid. Local and central vascular tone regulating systems were studied during that time. Brachial artery diameter and blood flow were recorded using ultrasonography and Doppler. Endothelial function was assessed with flow-mediated dilation. Results were compared with the same investigations performed under reference conditions in ambient air. During water immersion, brachial artery diameter increased (3.7 ± 0.2 mm in ambient air vs. 4 ± 0.2 mm in water immersion; p < 0.05). Endothelium-mediated dilation was significantly lower in water immersion than in ambient air (10% vs. 15%; p = 0.01). Nevertheless, the difference disappeared when the percentage vasodilatation of the brachial artery was normalized to the shear stimulus. Smooth muscle-mediated dilation was similar in the 2 conditions. Spectral analysis of systolic blood pressure variability indicated a decrease in sympathetic vascular activity. Plasma levels of nitric oxide metabolites remained unchanged, whereas levels of natriuretic peptides were significantly elevated. An increase in brachial blood flow, a decrease in sympathetic activity, a warming of the skin, and an increase in natriuretic peptides might be involved in the increase in reference diameter observed during water immersion. Endothelial cell reactivity and smooth muscle function did not appear to be altered.

Water immersion has long been known to produce marked diuresis, natriuresis, and kaliuresis and suppression of the renin-aldosterone system. These effects are mediated primarily by an increase in central blood volume. Immersion has therefore gained increased acceptance in human physiology for the investigation of the effects of central volume expansion on renal function and hormonal responsiveness without altering the composition of the extracellular fluid. An immersion tank used for studies in humans is described. Requisite features to ensure study reproducibility include a constant temperature, capability to alter the depth of immersion by adjusting water height, and the ability to maintain hygienic quality by means of constant circulation of the water through a sand filter. A constant temperature of 34.5 +/- 0.2 degrees C is maintained by thermostatically controlling the heat exchange to a unidirectional closed-circuit water system in the bottom of the immersion tank coursing through a stream source. The level of the water may be adjusted to any desired level by means of a waste line or an inlet of tap water.

The purpose was to determine whether extracellular volume or osmolality was the major contributing factor for reduction of thirst in air and head-out water immersion in hypohydrated subjects. Eight males (19-25 yr) were subjected to thermoneutral immersion and thermoneutral air under two hydration conditions without further drinking: euhydration in water (Eu-H2O) and euhydration in air, and hypohydration in water (Hypo-H2O) and hypohydration in air (3.7% wt loss after exercise in heat). The increased thirst sensation with Hypo-H2O decreased (P < 0.05) within 10 min of immersion and continued thereafter. Mean plasma osmolality (288 +/- 1 mosmol/kgH2O) and sodium (140 +/- 1 meq/l) remained elevated, and plasma volume increased by 4.2 +/- 1.0% (P < 0.05) throughout Hypo-H2O. A sustained increase (P < 0.05) in stroke volume accompanied the prompt and sustained decrease in plasma renin activity and sustained increase (P < 0.05) in plasma atrial natriuretic peptide during Eu-H2O and Hypo-H2O. Plasma vasopressin decreased from 5.3 +/- 0.7 to 2.9 +/- 0.5 pg/ml (P < 0.05) during Hypo-H2O but was unchanged in Eu-H2O. These findings suggest a sustained stimulation of the atrial baroreceptors and reduction of a dipsogenic stimulus without major alterations of extracellular osmolality in Hypo-H2O. Thus it appears that vascular volume-induced stimuli of cardiopulmonary baroreceptors play a more important role than extracellular osmolality in reducing thirst sensations during immersion in hypohydrated subjects.

Introduction. Exercise and head-out water immersion (HOI) have consistently reported an increase in central blood volume associated with the cephalad shift in blood volume. This causes an increase in left ventricular end diastolic volume and greater stroke volume during exercise compared to exercise in air at similar metabolic costs. In contrast, the metabolic response, specifically, blood lactate accumulation during exercise combined with HOI has yielded varying results depending on the mode of exercise. At present it appears that during exercise at similar metabolic costs, cycle ergometry exercise augments plasma lactate over treadmill running while HOI reduces the plasma lactate response to cycle ergometry exercise. The interaction between treadmill running and HOI appears less certain. Thus, we tested the hypothesis that running on a treadmill on land would result in a lesser accumulation of lactate than during HOI treadmill running. Methods. Eleven subjects' lactate thresholds were determined while running at a 0% grade at increasing speeds on a treadmill on land or during HOI on an underwater treadmill in a randomized cross-over design. Exercise tests were separated by a minimum of 3 days. Lactate concentrations were expressed in mM• kg-1 H2O after correcting for plasma solid concentration. During exercise changes in plasma volume were calculated from changes in hematocrit and hemoglobin. Lactate threshold was estimated from a log-log plot of lactate concentration (mM• kg-1 H2O) as a function of relative oxygen consumption (ml O2•min-1•kg-1 BW). Results. The energy cost and heart rate response to running at speeds between 5.5 and 7.5 mph was similar for land and HOI. During treadmill running on land, plasma volume decreased by 6.4 ± 4.0% at a speed of 7.5 mph. The decrease in plasma volume was significantly greater during HOI and averaged 18.7 ± 1.7% (p <0.05) at 7.5 mph. Plasma lactate was higher at any given treadmill speed ≥ 5.5 mph during HOI compared to land (p <0.05). Lactate threshold during HOI running (21.8 ± 1.6 mM• kg-1 H2O) was lower (p <0.05) than during running on the land treadmill (27.0 ± 1.6 mM• kg-1 H2O). Discussion. HOI running resulted in a consistent shift to the left (rise in plasma lactate occurred at a lower ) in the lactate threshold and elevated plasma lactate concentration at speeds between 5.5-7.5 mph despite similar metabolic and HR responses to the exercise.

The purpose of this study was to evaluate increased cardiac output (Q) on oxygen kinetics at exercise intensities above and below the lactate threshold (LT). We hypothesized the increase in Q using head-out water immersion (HOI) while treadmill running would reduce the rate constant of the fast component and reduce the amplitude of the slow component of oxygen kinetics compared with land treadmill running. Subjects (n=10) performed two 6 min exercise bouts at a 15% below and above the LT on a land and underwater treadmill following rest. A single exponential equation [VO2(t) = VO2(b) + A1•(1-e-t/TC1] was used to evaluate VO2. The slow component at the end of exercise was estimated by subtracting (VO2(b) + A1) from the plateau. The mean LT for HOI running 1.80 ± .09 L • min-1 was significantly lower (p < 0.05) than 2.15 ± 1.03 L • min-1 while running on the land. The Q during HOI exercise below and above the LT (16.5 ± 0.6 L • min-1, 18.0 ± 1.2 L • min-1) was significantly higher (p < 0.05) than the Q during exercise below and above the LT on land (11.5 ± 0.8 L • min-1, 13.0 ± 0.7 L • min-1). During HOI exercise below LT time to reach steady-state was delayed (8 ± 2 s). Exercise above LT showed similar phase one time constants for all exercise trials. The amplitude of the slow component was not influenced by HOI. As such, the increase in during HOI exercise did not hastening uptake kinetics.

INTRODUZIONE La ricerca scientifica ha da anni dimostrato che, tra pratica regolare di esercizio fisico e salute, esiste una relazione particolarmente significativa (Pate et al., 1995; US Department of Health and Human Service, 1996; Haskell et al., 2007). In particolare, alcune componenti della physical fitness (capacità aerobica, forza e resistenza muscolare, flessibilità, equilibrio ed una corretta composizione corporea) sembrano avere un ruolo chiave per il mantenimento della salute e dell’autonomia funzionale. Per tale ragione ed in funzione della specificità della risposta fisica agli stimoli allenanti, le più accreditate linee guida per la prescrizione dell’esercizio fisico (ACSM 1998, 2009) considerano competo (“well rounded”) quel training capace di indurre miglioramenti di tutte queste capacità fisiche includendo esercizi di resistenza cardiovascolare, forza, flessibilità ed equilibrio. Esse sottolineano inoltre che la selezione di un’appropriata attività fisica (in termini di tipologia, intensità, frequenza e durata), è presupposto fondamentale all’ottenimento di reali adattamenti organici, alla prevenzione degli infortuni ed all’aumento di aderenza ai protocolli di lavoro. Le attività di fitness acquatico (WA) hanno guadagnato negli ultimi dieci anni una straordinaria popolarità e rappresentano una delle possibili alternative tra le attività fisiche tradizionalmente dedicate al benessere ed alla salute. Ad oggi sono praticate da un numero sempre crescente di persone e da tipologie di individui dalle caratteristiche estremamente eterogenee (soggetti giovani ed anziani, individui sani ma anche affetti da patologie o limitazioni funzionali temporanee e/o permanenti, atleti in fase di recupero post-infortunio o in buona salute). Anche se, in letteratura, gli adattamenti organici (cronici ed acuti) a questa tipologia di esercizio fisico sono stati ampiamente discussi (e.g. Campbell et al., 2003; Takeshima et al., 2002; Colado et al., 2008; Colado et al., 2009 a and b; Barbosa et al., 2009), la valutazione dell’intensità d’esercizio in ambiente acquatico costituisce ancora un problema e questo è particolarmente evidente quando le attività fisiche considerate si presentano complesse da un punto di vista tecnico e/o quando si tenta di definire l’intensità in condizioni non rigidamente controllate. Ad oggi, le conoscenze e gli strumenti necessari a definire con precisione l’intensità d’esercizio, a pianificare un programma adatto a soggetti dalle caratteristiche diverse ed a monitorare i risultati di un training di fitness acquatico, non risultano sufficienti. SCOPI Il presente lavoro si pone l’obiettivo di definire più precisamente il ruolo che le attività di fitness acquatico possono rivestire per il benessere e la salute delle persone e di capire se, questa tipologia di esercizio fisico, può costituire un allenamento completo (“well rounded”) in riferimento ai requisiti proposti dall’ American College of Sport Medicine. La tesi include tre studi. •Il primo studio si è occupato di quantificare l’intensità (EI) dei più comuni esercizi di fitness acquatico (WE) eseguiti a tre differenti frequenze di movimento (f1 = 1.8-2.0 Hz; f2 = 2.0-2.2 Hz; f3 = 2.2-2.4 Hz) ed ad ampiezza standardizzata e controllata. Successivamente è stata quantificata l’intensità di una combinazione di questi esercizi eseguiti a data frequenza. •Il secondo studio si è occupato di programmare un WE training di intensità nota e della durata di nove settimane e di verificarne l’efficacia sulle componenti della physical fitness (capacità aerobica, forza e resistenza muscolare, flessibilità, equilibrio ed una corretta composizione corporea) maggiormente correlate alla salute. •Il terzo studio si è occupato di confrontare differenti tecniche di misura e di stima dell’intensità di esercizio durante fitness acquatico. STRUTTURA DELLA TESI La tesi si presenta divisa in quattro capitoli. Il primo capitolo comprende: un’introduzione generale al lavoro (sezione 1.1), una sintesi delle principali caratteristiche dell’ambiente acquatico (sezione 1.2) e la presentazione dei più importanti adattamenti fisiologici dell’organismo umano all’immersione in atteggiamento verticale (sezione 1.3). Successivamente vengono descritte (sezione 1.4) e classificate (sezione 1.5) le più comuni attività di fitness acquatico e viene presentata la letteratura specificatamente dedicata a questa tipologia di esercizio fisico (sezione 1.6). I metodi utili a misurare e/o stimare l’intensità dell’esercizio fisico sono discussi in generale nella sezione 1.7 ed in relazione alle attività di fitness acquatico nella sezione 1.8. In ultimo sono schematicamente riassunti i principali obiettivi dello studio (sezione 1.9). Il secondo capitolo è dedicato all’introduzione (sezione 2.1) del primo studio (“Exercise Intensity of head-out water based activities (water fitness)”), ai materiali e metodi utilizzati durante il lavoro (sezione 2.2), ai risultati ottenuti (sezione 2.3) ed alla loro discussione (sezione 2.4 e sezione 2.5). Il terzo capitolo è dedicato all’introduzione (sezione 3.1) del secondo studio (“Water-based training enhance both physical capacities and body composition in healthy young adult women”), ai materiali e metodi utilizzati durante il lavoro (sezione 3.2), ai risultati ottenuti (sezione 3.3) ed alla loro discussione (sezione 3.4 e sezione 3.5). Il quarto capitolo è dedicato all’introduzione (sezione 4.1) del terzo studio (“Monitoring intensity during water based activities (head-out immersion): a comparison among different measurement techniques”), ai materiali e metodi utilizzati durante il lavoro (sezione 4.2), ai risultati ottenuti (sezione 4.3) ed alla loro discussione (sezione 4.4 e sezione 4.5). Al termine della tesi è compresa una discussione generale dei risultati ottenuti dagli studi precedentemente descritti ed una definizione del ruolo che le attività di fitness acquatico possono rivestire per il benessere ed il mantenimento della salute in linea con lo scopo generale del lavoro.
BACKGROUND A strong relationship between regular physical activity and health has been clearly established (Pate et al., 1995; US Department of Health and Human Service, 1996; Haskell et al., 2007). Particularly, some components of physical fitness such as cardiovascular endurance, muscular strength and endurance, flexibility, balance and a correct body composition seem to be strong health-related variables. The guidelines of the American College of Sport Medicine (1998; 2009) place a strong emphasis on these components of physical fitness and underline that, given the specific nature of exercise adaptation, a “well rounded” training program should consist of aerobic, resistance and flexibility exercises. The existing evidence concerning exercise prescription also underlines that the selection of an appropriate physical activity (in terms of exercise mode, intensity, frequency and duration) is essential in order to obtain actual training effects, to avoid injuries and to ensure exercise adherence. Water based activities (WA), in recent years, gained popularity and are considered as one of the possible alternatives among the traditional physical activities for well-being and health. These activities are performed by different types of subjects: young and adult healthy individuals who regularly take part in recreational training but also individuals with low levels of physical fitness (such us elderly people, subjects with orthopaedic or neurological disabilities, athletes with surgically, or otherwise, treated injuries and obese persons). Even if the physiological responses and training effects of WA have been investigated by several authors in different populations (e.g. Campbell et al., 2003; Takeshima et al., 2002; Colado et al., 2008; Colado et al., 2009 a and b; Barbosa et al., 2009), the accurate assessment of intensity during “water exercises” performed without specific equipment is not a simple task, expecially in a field setting, during water based classes. Thus, at present, there are still no sufficient tools to define the work intensity, to plan a training program adapted to different subjects and to monitor and verify the training effects of WA. AIM The aim of this doctoral Thesis is therefore to better define the role of water based activities for public health and to better understand whether these physical activities can be considered a “well rounded” training program according to the American College of Sport Medicine recommendations. The present work includes three studies. •The aim of the first study was to make a further step in the comprehension of the exercise intensity (EI) during water based activities by: i) measuring the exercise intensity of the most common water based exercises (WE) at different movement frequencies (f1 = 1.8-2.0 Hz; f2 = 2.0-2.2 Hz; f3 = 2.2-2.4 Hz) and at a standardize movement’s amplitude; ii) measuring EI during a combination (MIX) of these WE. •The aim of the second study was to determine the effectiveness of a nine weeks aquatic training program of known intensity (EI) on aerobic capacity, muscle strength, flexibility, balance and body composition, in healthy young adult women. •The aim of the third study was to compare different measurement techniques to estimate physical activity intensity during water based activity. STRUCTURE OF THE THESIS This Thesis is divided in four chapters. The first chapters includes a general introduction to the problem (section 1.1), a brief summary of the aquatic environment characteristics (section 1.2) and a section dedicated to the more important physiological adjustment to head-out immersion (section 1.3). In this first part of Thesis, the water based activities are also presented (section 1.4) and classified (section 1.5) in order to better define the characteristics of the water fitness exercises. The related scientific background is thus reviewed and discussed (section 1.6). Finally, the assessment of exercise intensity is discussed in general terms (section 1.7) as well as in regard to the physical activity performed in water (section 1.8). At the and of this chapter, the main aims of the three studies are schematically reported (section 1.9). In the second chapter, the study entitled “Exercise Intensity of head-out water based activities (water fitness)” is presented. After a brief introduction (section 2.1), the materials and methods (section 2.2) are explained in detail and the results are illustrated (sections 2.3). Finally, the results are discussed (section 2.4 and 2.5). In the third chapter, the study entitled “Water-based training enhance both physical capacities and body composition in healthy young adult women” is presented. After a brief introduction (section 3.1), the materials and methods (section 3.2) are explained in detail and the results are illustrated (sections 3.3). Finally the results are discussed (section 3.4 and 3.5). In the fourth chapter, the study entitled “Monitoring intensity during water based activities (head-out immersion): a comparison among different measurement techniques” is presented. After a brief introduction (section 4.1), the materials and methods (section 4.2) are explained in detail and the results are illustrated (sections 4.3). Finally the results are discussed (section 4.4 and 4.5). At the end of this Thesis, a general discussion of the results obtained in the three studies is reported to better define the role of water based activities for public health and to better understand whether these physical activities can be considered a “well rounded” training program (according to American College of Sport Medicine recommendations), in line with the main aim of this work.

The American Revolution inspired new movements with a longing to restore what they believed was a primitive and pure form of the church, uncorrupted by the accretions of the centuries. Unlike most Canadians, Americans were driven by the rhetoric of human equality, in which individual believers could dispense with creeds or deference to learned ministers. This chapter argues that one manifestation of this was the Restorationist impulse: the desire to recover beliefs and practices believed lost or obscured. While that impulse could be found in many Protestant bodies, the groups classified as ‘Restorationist’ in North America emerged from what is today labelled the Stone-Campbell movement. They were not known explicitly as Restorationists as they identified themselves as ‘Christian Churches’ or ‘Disciples of Christ’ in a bid to find names that did not separate them from other Christians. The roots of this movement lay in the Republican Methodist Church or ‘Christian Church’ founded by James O’Kelly on the principle of representative governance in church and state. As its ‘Christian’ title implied, the new movement was supposed to effect Christian unity. It was carried forward in New England by Abner Jones and Elias Smith who came from Separate Baptist congregations. Smith was a radical Jeffersonian republican who rejected predestination, the Trinity, the divinity of Christ, and original sin as human inventions and would be rejected from his own movement when he embraced universalism. The Presbyterian minister Barton W. Stone was the most important advocate of the Christian movement in Kentucky and Tennessee. Stone was a New Light Presbyterian who fell out with his church in 1803 because he championed revivals to the displeasure of Old Light Presbyterians. With other ministers he founded the Springfield Presbytery and published an Apology which rejected ‘human creeds and confessions’ only to redub their churches as Christian Churches or Churches of Christ. Stone’s movement coalesced with the movement founded by Alexander Campbell, the son of an Ulster Scot who emigrated to the United States after failing to effect reunion between Burgher and Anti-Burghers and founded an undenominational Christian Association. Alexander embraced baptism by immersion under Baptist influence, so that the father and son’s followers were initially known as Reformed (or Reforming) Baptists. The increasing suspicion with which Baptists regarded his movement pushed Alexander into alliance with Stone, although Campbell was uneasy about formal terms of alliance. For his part, Stone faced charges from Joseph Badger and Joseph Marsh that he had capitulated to Campbell. The Stone-Campbell movement was nonetheless successful, counting 192,000 members by the Civil War and over a million in the United States by 1900. Successful but bifurcated, for there were numerous Christian Churches which held out from joining the Stone-Campbell movement, which also suffered a north–south split in the Civil War era over political and liturgical questions. The most buoyant fraction of the movement were the Disciples of Christ or Christian Churches of the mid-west, which shared in the nationalistic and missionary fervour of the post-war era, even though it too in time would undergo splits.

Social Virtual Reality (VR) applications enable real-time interpersonal conversation and allow users to perform activities together. They have the potential of changing the ways learners practise speaking a foreign language. Following a previous study (Jauregi Ondarra, Gruber, & Canto, 2020), we designed the present study to explore how presence, immersion, and interactivity affect overall social experience. Students from Germany and the Netherlands engaged in High-immersion VR (HiVR) virtual exchange sessions, using Spanish as a lingua franca at A2 level. International dyads carried out four interaction tasks in AltspaceVR, using head-mounted devices. To examine students’ HiVR virtual exchange experiences, different sources of data were gathered: questionnaires, reflection diaries, recordings, and focus group interviews. The preliminary results, based on the surveys and reflection journals, show that students liked to use a social VR app to communicate in the target language with peers from other countries, as they felt completely immersed and co-present in the social interactive VR space. This might enhance engagement and lower anxiety levels.

Virtual reality involves the creation of multisensory experience of an environment (its space and events) through artificial, electronic means; but that environment incorporates a sufficient number of features of the non-artificial world that it is experienced as “reality.” The cognitive issues of virtual reality are those that are involved in knowing and understanding about the virtual environment (cognitive: to perceive and to know). The knowledge we are concerned with in this chapter is both short term (Where am I in the environment? What do I see? Where do I go and how do I get there?), and long term (What can and do I learn about the environment as I see and explore it?). Given the recent interest in virtual reality as a concept (Rheingold, 1991; Wexelblat, 1993; Durlach and Mavor, 1994), it is important to consider that virtual reality is not, in fact, a unified thing, but can be broken down into a set of five features, any one of which can be present or absent to create a greater sense of reality. These features consist of the following five points. 1. Three-dimensional (perspective and/or stereoscopic) viewing vs. two-dimensional planar viewing. (Sedgwick, 1986; Wickens et al., 1989). Thus, the geography student who views a 3D representation of the environment has a more realistic view than one who views a 2D contour map. 2. Dynamic vs. static display. A video or movie is more real than a series of static images of the same material. 3. Closed-loop (interactive or learner-centered) vs. open-loop interaction. A more realistic closed-loop mode is one in which the learner has control over what aspect of the learning “world” is viewed or visited. That is, the learner is an active navigator as well as an observer. 4. Inside-out (ego-referenced) vs. outside-in (world-referenced) frame-of-reference. The more realistic inside-out frame-of-reference is one in which the image of the world on the display is viewed from the perspective of the point of ego-reference of the user (that point which is being manipulated by the control). This is often characterized as the property of “immersion.” Thus, the explorer of a virtual undersea environment will view that world from a perspective akin to that of a camera placed on the explorer’s head;

Computer game technology is poised to make a significant impact on the way our youngsters will learn. Our youngsters are ‘Digital Natives’, immersed in digital technologies, especially computer games. They expect to utilize these technologies in learning contexts. This expectation, and our response as educators, may change classroom practice and inform curriculum developments. This chapter approaches these issues ‘head on’. Starting from a review of the current educational issues, an evaluation of educational theory and instructional design principles, a new theoretical approach to the construction of “Educational Immersive Environments” (EIEs) is proposed. Elements of this approach are applied to development of an EIE to support Literacy Education in UK Primary Schools. An evaluation of a trial within a UK Primary School is discussed. Conclusions from both the theoretical development and the evaluation suggest how future teacher-practitioners may embrace both the technology and our approach to develop their own learning resources.

When I was seven years old, I once got lost in the forest. I had been following my father, who walked faster than me, on our way through the trees behind our house to meet someone in the tribal village. At a certain point, I realised that I couldn’t hear my father’s footsteps in front of me – sounds that I had been tracing while looking around in curiosity. I had been taken by the sunlight as it played on the leaves and butterflies as they passed by in solemn unison with the green leaves and dark tree branches. Then, I found myself alone. The murmurs of wind blowing through leaves and the friction between movement and stasis had already drowned out my father’s footsteps – my lone sonic navigational tool in the forest. Their absence accentuated other sounds. The intimate whispering wind carrying news of fallen leaves, its intensity and proximity suddenly sounded ominous and dreadful. Surrounded by this maze of sound, I lost my sense of orientation and security. I wanted to escape this estranging sonic immersion to find familiar voices that would ground me. By retracing my footsteps, I gradually found a way out of the vibrating forest. My guiding force had been a heightened relationship with the forest’s sound world and my isolation. Ambient sounds and the reflection of my own anxious voice among the dense trees had allowed me to navigate through the labyrinthine green and escape....

When my wife Joan and I were newly married, we lived in a north Jersey suburb not far from the New York state line. Every weekday morning we drove down the Palisades Interstate Parkway to the George Washington Bridge and crossed the Hudson River to Manhattan, where I taught and Joan was a graduate student. The parkway runs along the Palisades, a magnificent, igneous bluff that flanks the west bank of the Hudson and faces, on the far shore, Yonkers, the Riverdale section of the Bronx, and Manhattan. Wooded parkland extends on both sides of the road for its entire length until just before the approach to the bridge, where many lanes of superhighway converge on the toll booths. We loved the woods along the parkway—they calmed us before our immersion in the chaotic city, and soothed us when we left it at the end of the day. That was before we went on our honeymoon, a three-week hike on the Appalachian Trail (interspersed with some hitchhiking on country roads), from Springer Mountain, Georgia, to the border of the Great Smokies in North Carolina. The forest we walked through was a mixture of tall pines and an incredible variety of native hardwoods—an experience of natural diversity that was overwhelming. Nearly every tree we saw was new to us, yet we could feel the pattern and cohesiveness of the forest as a whole. Rhododendrons formed a closed canopy over our heads, fragmenting the June sunshine into a softly shifting mosaic of dap-pled patches. We stepped on a carpet of rhododendron petals. The trip was over all too quickly. The plane carrying us back de-scended through a dense inversion layer of black smog before touching down on the runway at Newark. Home. We were depressed and silent. The ride from Newark Airport to our house took us on the Palisades Parkway. For the first time, we became aware that the woods along the park way were dominated by thin, ungainly Ailanthus, with their coarse(and, we knew, rank-smelling) foliage, and by other weedy species such as the lanky Paulownia. Suddenly, these exotic species seemed very much out of place.

The wet chemical processing opens the way to deposit thin film with the versatility and ease for a variety of materials. Liquid film deposition involves the application of a liquid precursor on a substrate which is then converted to the required coating material in a subsequent post-treatment step. Different non-vacuum solution based deposition techniques have been developed to grow thin films with high efficiency and functionality. Spin coating is one of an effective technique for thin film fabrication due to low cost, uniformity, less hazardous, and capability of easy scaling up. The typical process involves depositing a small amount of a fluid onto the center of a substrate and then spinning the substrate at high speed. Dip coating is another simple, cost effective route with feasibility to scale-up for commercial production. The dip coating process can be divided into three important technical stages, immersion, withdrawal and evaporation. The coating may be subjected to further heat treatment in order to burn out residual compounds and induce crystallization of the functional oxides. Spray coating is a promising technique to grow thin film in research and industry to prepare thin and thick films. It is an easy approach to fabricate thin film with uniform distribution at small scale from a few nanometers to micrometers in thickness. Inkjet printing is the emerging promising technique to develop large-scale, and flexible thin films. The inkjet printing process allow easy customization to grow variety of complex structures.

The Child and Adolescent Statute, at 30, still breathes hope. Law 8.069 / 1990 still lacks due recognition from the institutions that make up the whole of society; citizens who are part of marginalized communities; in addition to the bodies that make up the rights guarantee networks. In this context, it is up to the funding agencies to implement knowledge socialization activities in the communities where they operate, with the support of basic education institutions up to the Universities. The text presented below intends to resume some ideas disseminated at the VII Paraná State Seminar held in November 2020, which denotes the concern about guaranteeing rights for children and adolescents in times of democratic losses in reference to human rights. In a process of pandemic and economic stress, where education and health, in Brazil, suffers a technical, political and scientific neglect, all types of violence (physical or symbolic) are maximized, in which children and adolescents are inserted, a reality that regardless of social class. In addition to bringing the main ideas of the seminar to the debate, the analysis will be guided by authors who can contribute to the desired depth. The results of this immersion intend to impress the relevance in the care and protection of children and adolescents from the cities to the traditional communities, identifying and systematizing the main actions pointed out in the seminar, object of our bibliographic and eventual investigation. Faced with the socio-cultural and socio-educational tangle that we face today, the human values ​​of solidarity, collaboration and respect for life with equity begin to have a greater meaning. Authors such as Gohn (2011), Caliman (2010) support the reflections on socio-cultural and socio-educational contexts. The analysis of social policies specifically referring to ECA will be based on Perez and Passoni (2010); Farinelli and Pierinni (2016). The methodological process is based on the qualitative conception of research aiming at the reliability of the debates in the exposition tables, Minayo (2002). The Federal Constitution (1988) and Paganini (2011) support the study on the guarantee of fundamental rights in which the five axes of ECA are cemented.

In recent years, a number of prototypical demonstrators have shown that augmented reality has the potential to improve manual work processes as much as desktop computers and office tools have improved administrative work (Azuma et al., 2001; Ong & Nee, 2004). Yet, it seems that the “classical concept” of augmented reality is not enough (see also http://www.ismar05.org/IAR). Stakeholders in industry and medicine are reluctant to adopt it wholeheartedly due to current limitations of head-mounted display technology and due to the overall dangers involved in overwhelming a user’s view of the real world with virtual information. It is more likely that moderate amounts of augmented reality will be integrated into a more general interaction environment with many displays and devices, involving tangible, immersive, wearable, and hybrid concepts of ubiquitous and wearable computing. We call this emerging paradigm ubiquitous augmented reality (UAR) (MacWilliams, 2005; Sandor, 2005; Sandor & Klinker, 2005). It is not yet clear which UAR-based humancomputer interaction techniques will be most suitable for users to simultaneously work within an environment that combines real and virtual elements. Their success is influenced by a large number of design parameters. The overall design space is vast and difficult to understand. In Munich, we have worked on a number of applications for manufacturing, medicine, architecture, exterior construction, sports, and entertainment (a complete list of projects can be found at http://ar.in.tum.de/Chair/ProjectsOverview). Although many of these projects were designed in the short-term context of one semester student courses or theses, they provided insight into different aspects of design options, illustrating trade-offs for a number of design parameters. In this chapter, we propose a systematic approach toward identifying, exploring, and selecting design parameters at the example of three of our projects, PAARTI (Echtler et al., 2003), FataMorgana (Klinker et al., 2002), and a monitoring tool (Kulas, Sandor, & Klinker, 2004). Using a systematic approach of enumerating and exploring a defined space of design options is useful, yet not always feasible. In many cases, the dimensionality of the design space is not known a-priori but rather has to be determined as part of the design process. To cover the variety of aspects involved in finding an acceptable solution for a given application scenario, experts with diverse backgrounds (computer science, sensing and display technologies, human factors, psychology, and the application domain) have to collaborate. Due to the highly immersive nature of UAR-based user interfaces, it is difficult for these experts to evaluate the impact of various design options without trying them. Authoring tools and an interactively configurable framework are needed to help experts quickly set up approximate demonstrators of novel concepts, similar to “back-of-the-envelope” calculations and sketches. We have explored how to provide such first-step support to teams of user interface designers (Sandor, 2005). In this chapter, we report on lessons learned on generating authoring tools and a framework for immersive user interfaces for UAR scenarios. By reading this chapter, readers should understand the rationale and the concepts for defining a scheme of different classes of design considerations that need to be taken into account when designing UAR-based interfaces. Readers should see how, for classes with finite numbers of design considerations, systematic approaches can be used to analyze such design options. For less well-defined application scenarios, the chapter presents authoring tools and a framework for exploring interaction concepts. Finally, a report on lessons learned from implementing such tools and from discussing them within expert teams of user interface designers is intended to provide an indication of progress made thus far and next steps to be taken.

The Spatial Audio Data Immersive Experience (SADIE) project aims to identify new foundational relationships pertaining to hu-man spatial aural perception, and to validate existing relation-ships. Our infrastructure consists of an intuitive interaction in-terface, an immersive exocentric sonification environment, and a layer-based amplitude-panning algorithm. Here we highlight the system’s unique capabilities and provide findings from an initial externally funded study that focuses on the assessment of human aural spatial perception capacity. When compared to the existing body of literature focusing on egocentric spatial perception, our data show that an immersive exocentric environment enhances spatial perception, and that the physical implementation using high density loudspeaker arrays enables significantly improved spatial perception accuracy relative to the egocentric and virtual binaural approaches. The preliminary observations suggest that human spatial aural perception capacity in real-world-like immersive exocentric environments that allow for head and body movement is significantly greater than in egocentric scenarios where head and body movement is restricted. Therefore, in the design of immersive auditory displays, the use of immersive exocentric environments is advised. Further, our data identify a significant gap between physical and virtual human spatial aural perception accuracy, which suggests that further development of virtual aural immersion may be necessary before such an approach may be seen as a viable alternative.

An experimental investigation of a scheme for cooling electronics packaged in a 3D stack arrangement will be presented in this paper. The scheme utilizes immersion cooling of the stacked electronics in an enclosure filled with a dielectric fluid. Convection and conduction within the dielectric fluid drive heat from the 3D stack to the walls of the enclosure from where a ‘synthetic jet /fan air-cooled heat sink’ ultimately dissipates heat to the ambient. Four layers of thick film heaters embedded in FR-4 sheets, each attached to thin copper plates (innovatively stacked in a pyramidal arrangement for conducting heat laterally to the dielectric fluid and simultaneously promoting natural convection in the fluid), were used to simulate a 3D stack of electronics. For a comparative study, several runs were carried out, where the enclosure was filled with dielectric fluid (FC-770), FC-770 in combination with copper wool (with a goal of enhancing heat transfer in FC-770), and water. For a 40 W total power input to the stack, it was observed that the thermal resistance for heat dissipation to ambient from the four heaters varied from 1.67 K/W to 1.96 K/W with FC-770, 1.47 K/W to 1.87 K/W with FC-770 combined with copper wool, and 1.06 K/W to 1.50 K/W with water. The proposed cooling solution is passive and scalable, and is demonstrated to be practicable and effective in cooling 3D stacked electronics.

A through-chip porous Ru-Pt catalyst layer was fabricated on a Si wafer and a novel miniature DMFC (Direct Methanol Fuel Cell) was realized. Recently, we found that porous noble metal layer can be synthesized on Si substrate by immersion plating on a porous Si. In order to realize a DMFC with our novel structure, a porous Ru layer was synthesized on the Si substrate using the immersion plating on the porous Si, then Pt was deposited by galvanic replacement reaction on the porous Ru. The porous Ru-Pt structure showed catalytic activity on methanol oxidization. A through-chip porous Ru-Pt layer was fabricated on a Si wafer by plasma etching and monolithic electrodes with catalyst layers and fuel channels were realized. A preliminary DMFC prototype successfully demonstrated power generation of 2mW/cm2.

In this article, we present the numerical simulation of a real cylinder head quenching cooling process using a newly developed approach for immersion quenching described in Part I of this research. Computational grids, consisting of 1.6 million cells in the coolant (liquid) domain and 1.5 million cells in the solid region, are utilized to perform the ACCI coupled quenching simulation implemented in the commercial code AVL-FIRE framework. Multitude of flow features such as vapor pocket generation, bubble clustering and their disposition are captured very effectively during the computation. Comprehensive descriptions of the flow field information and the temperature pattern in the solid at different time instants are provided. A comparison of the registered temperature readings at different monitoring locations with the numerical results generates an overall very good agreement. Our results indicate the presence of intense non-uniformity in the temperature distribution within the solid region which is of grave importance in evaluating the stress and fatigue patterns generated in the quenched object. The capability of the quenching model in simulating a real-time immersion quenching application process and the efficiency in reducing the overall model size by the application of the ACCI procedure is well demonstrated.

This paper describes development and application of Phased Array Ultrasonic Testing (UT) and Remotely Operated Vehicles (ROV) for In-Vessel Internals Inspection. Stress Corrosion Crack (SCC) on reactor internals is one of the most important issues since 1990s, and demand to inspect the reactor internals is increasing. Instrument manufactures and inspection venders have developed and applied 1) Phased Array UT technologies and technique as one of our Non-Destructive Examination (NDE) technologies, 2) several kinds of ROVs and special tools for probe delivery and positioning. They are available and effective in In-Vessel Inspection (IVI) and maintenance, which shall be conducted in the narrow room under water. Furthermore, the UT technique for Alloy 182 weld that used to be difficult to detect and size flaws was developed and deployed in the BWR IVI. UT experiences in reactor vessels are increasing in recent years. An immersion technique by Phased Array UT is a key to perform the In-vessel UT on a complex geometric surface to be inspected, and to achieve very wide accessible range by ROVs or simple special tools efficiently. Advantages of the water immersion method and a ROV development result are shown in this paper. Particularly, TOSHIBA developed a flat type ROV for Shroud (Shroud ROV), which can be held against the surface of the shroud by thrusting propellers and scan mechanically through narrow gap within 2 inches {50mm}. The ROV’s positioning accuracy and applications for Shroud UT are shown. As the field experience, this introduces the UT results for CRD Stub tube Alloy 182 weld that is located on the vessel bottom head in Hamaoka UNIT 1 of Chubu Electric Power Company in Japan. An axial SCC flaw was detected by underwater visual testing, after the CRD stub tube leakage was detected. Then UT examination for the flaw was accomplished on the Alloy 182 weld in the vessel. We evaluated that the flaw penetrated into the weld metal of the CRD stub tube-pat weld and didn’t propagate into the low alloy of Reactor Pressure Vessel base metal. After UT sizing, the CRD stub tube was removed and replaced. The examination result was proven to have a good agreement with the actual crack depth. As a result, the efficiency of our Phased Array Technique was confirmed. As the other immersion method application, UT coverage example and accessible range for Shroud inspection are shown.

Traditional thermal management techniques such as air-cooled plate- and pin-fin heat sinks are today being pushed to their limits by the increasing power densities of computing hardware (power supplies, controllers, processors, and integrated circuits). In comparison, direct immersion cooling within an alternative cooling medium such as commercial dielectric fluids offers the ability to handle high power densities while also accommodating tighter printed circuit board spacing. Together, these attributes are critical to facilitating higher computing densities. However, this type of high density setup also requires that any heat sink present be low profile so as to not obstruct adjacent printed circuit boards. Such a stringent limit on heat sink height can make achieving cooling targets challenging with existing designs. In this work, the performance of several low profile (height less than 6 mm) heat sinks of varying design are evaluated within a carefully controlled direct immersion cooling environment. Commercial copper heat sinks fabricated through conventional manufacturing (CM) approaches serve as baselines for these performance tests. These same heat sink designs are also replicated via additive manufacturing (AM) utilizing a conductive, carbon-filled printable polylactic acid (PLA) composite material. The performance of these AM heat sinks are then compared to the CM heat sinks, with special emphasis on differences in thermal conductivity between the constituent materials. Finally, novel bio-inspired heat sink designs are developed which would be difficult or impossible to achieve using CM approaches. The most promising of these designs were then created using AM and their performance evaluated for comparison. The overall goal of this is to ascertain whether the design and fabrication flexibility offered by AM can facilitate low profile heat sink designs that can meet or exceed the performance of conventional heat sinks even with perceived deficiencies in material properties for AM parts. Experiments were carried out within Novec 7100 dielectric fluid for single-phase natural convection scenarios as well as two-phase subcooled boiling conditions at atmospheric pressure. A custom test rig was constructed consisting of mirror-polished stainless steel plates and polycarbonate viewing ports to allow visual access. A rotating sample stage allows for data to be obtained at varying heat sink orientation angles from 0° to 90°. For two-phase experiments, multi-angle video capture allows for analysis of the two-phase dynamics occurring at the heat sink samples to be visualized and temporally linked to the associated temperature and heat flux data.

In this article, we describe a newly developed modeling procedure to simulate the immersion quench cooling process using the commercial code AVL-FIRE. The boiling phase change process, triggered by the dipping hot solid part into a subcooled liquid bath and the ensuing two-phase flow is handled using an Eulerian two-fluid method. Mass transfer effects are modeled based on different boiling modes such as film or nucleate boiling regime prevalent in the system. Separate computational domains constructed for the quenched solid part and the liquid (quenchant) domain are numerically coupled at the interface of the solid-liquid boundaries using the AVL-Code-Coupling-Interface (ACCI) feature. The advanced ACCI procedure allows the information pertaining to the phase change rates in the liquid domain to appear as cooling rates on the quenched solid boundaries. As a consequence, the code handles the multiphase flow dynamics in the liquid domain in conjunction with the temperature evolution in the solid region in a tightly coupled fashion. The methodology, implemented in the commercial code AVL-FIRE, is exercised in simulating the quenching of solid parts. In part I of the present research, phase change models are validated by simulating a work piece quenching process for which measurement data are available for various water temperature ranging from 20C to 80C. The computations provide a detailed description of the vapor and temperature fields in the liquid and solid domain at various time instants. In particular, the modifications arising in the liquid-vapor flow field in the near vicinity of the solid interface as a function of the boiling mode is well accommodated. The temperature history predicted by our model at different monitoring points, under different subcooling conditions, correlate very well with the experimental data wherever available. In part II, the model is further applied to real engine cylinder head quenching process and assessment is made for the cooling curves for various measuring points. Overall, the predictive capability of the new quenching model is well demonstrated.

The ability to eliminate freezing damage using “vitrification” (or the formation of glass) has long been an area of intense interest in cryobiology. Typically vitrification is achieved when biological systems are cooled at rates ranging from ∼8,000 °C/min to ∼10,000 °C/min [1–5]. Using traditional cooling methods (immersion in liquid nitrogen), such high cooling rates are currently not achievable, in large tissue sections (∼cm’s). In the present study we investigate a novel method to achieve high cooling rates in large tissue sections by pulsed laser heating in conjunction with cryogenic temperatures, i.e. high cooling rates are achieved by the localized difference in temperature between the laser heated tissue (∼1000’s of °C) and the surrounding liquid nitrogen (∼−160 °C). Additionally, the use of pulsed lasers allows localized heating of the tissue coupled with small time scales of energy deposition (0.1 to 1 pico seconds) such that the heating/thermal damage in tissues is minimized. To amplify this idea further, we developed a numerical model to predict the temperature transients in tissues exposed to laser heating and cryogenic temperatures. Analysis of our numerical simulations suggest that a perturbation of ∼3500 °C in a 5mm thick tissue leads to cooling rates in excess of ∼8000 °C/min throughout the tissue slice. These results indicate the possibility of vitrifying large tissue sections of cryobiological relevance using a combination of laser heating and liquid nitrogen cooling.

Abstract Networking and computing dependency has been increasing in the modern world, thus, boosting the growth of data centers in leading business domains like banking, education, transportation, social media etc. Data center is a facility that incorporates an organization’s IT operations and equipment, as well as where it stores, processes and manages the data. To fulfill the increasing demands of data storage and data processing, a corresponding increase in server performance is needed. This causes a subsequent increment in power consumption and heat generation in the servers due to high performance processing units. Currently, air cooling is the most widely used thermal management technique in data centers, but it has started to reach its limitations in cooling high packaging densities. Therefore, industries are looking for single-phase immersion cooling using various dielectric fluids to reduce the operational and cooling costs by enhancing the thermal management of servers. This research work aims at increasing the rack density by reducing the form factor of a 3rd Generation Open Compute Server using single-phase immersion cooling. A computational study is conducted in the operational range of temperatures and the thermal efficiency is optimized. A parametric study is conducted by changing the inlet velocities and inlet temperatures of cooling liquid for different heights of the open compute 3rd generation server. A comparative study is then carried out for white mineral oil and synthetic fluid (EC100).

An increasing density of data stored on an optical disk requires better writing and reading control, more sophisticated data processing, and smaller laser beam stylus. An optical head can produce a smaller beam stylus by using a shorter wavelength laser diode and/or by increasing the numerical aperture (NA) of an objective lens. While the usage of a shorter wavelength is clearly curtailed by availability of short wavelength diodes, the upper limit on the NA may not be determined by constraints associated with the lens design and manufacturing. Particularly, when the recording surface of an optical disk is protected with a substrate, the upper NA limit may be dependent on disk tolerances and on the capability of a drive servo control. When the solid immersion lens (SL) technique is used, the upper NA limit depends more on the optical system design ingenuity and on the magnitude of the refractive index n of a SL lens. In the SL case the disk without substrate suffers with far less flaws. Our interest here will be in optical heads working with substrate furnished disks displaced more than one millimeter from a biaspheric objective lens.