Measurement of thermal accommodation coefficients of steel surfaces

The thermal accommodation coefficient plays an important role in low density thermal energy transfer measurement. The object of this investigation was to measure the thermal energy transfer between a heated test surface and a water cooled reference surface (flat black lacquer) consisting of two infinite concentric cylinders separated by dry air. Two machined and sanded steel cylinders with mean surface roughnesses of 25 microinches and 7.5 microinches were used as the test surfaces . Measurements were made in the pressure range of 1.2 x 10⁻⁶ mm Hg. to 1.8 x 10⁻⁶ mm Hg. and temperature range for test cylinders of 110°- 200. 2°F. in determining the emittance. The pressure range was 1.0 x 10⁻³ mm Hg. to 1.35 x 10⁻³ mm Hg. and the temperature range 115.5° -197.6° F. in determining the thermal accommodation coefficients. The thermal accommodation coefficient for dry air on a steel surface with an average mean surface roughness of 25 microinches was 0.835 (emittance was 0.174) while for the 7.5 microinches surface condition, the thermal accommodation coefficient was 0.693 (emittance was 0.123). The experimental data indicated that for the same material, the rougher surface will have a higher value of thermal accommodation coefficient and emittance. The experimental results agree closely with those of classical theory (roughness causes more than one collision at the surface) and with some other investigators (2 & 7). The accuracy of the results as well as the experimental deviations are within the accepted engineering limits for this type of measurement --Abstract, Pages ii-iii

Association of Early Blood Pressure Decrease and Renal Function With Prognosis in Acute Heart Failure

OBJECTIVES The aim of this study was to investigate the association between systolic blood pressure (SBP) drop, worsening renal function (WRF), and prognosis in patients with acute heart failure (AHF). BACKGROUND A large drop in SBP early after hospital admission for AHF might be associated with increased risk for WRF and prognosis. However, there is a paucity of data regarding the interaction between WRF and a drop in SBP on clinical outcomes. METHODS A post hoc analysis among 6,544 patients with AHF enrolled in the RELAX-AHF-2 (Relaxin in Acute Heart Failure-2) trial was performed. Blood pressure was uniformly and repetitively measured. Peak SBP drop was defined as the difference between baseline SBP and lowest SBP documented during the first 48 hours. WRF was defined by an increase in serum creatinine of $0.3 mg/dL from baseline to day 5. RESULTS Peak SBP drop was independently associated with a higher risk for WRF (HR: 1.11 per 10 mm Hg SBP drop; P < 0.001), 5-day worsening heart failure (HR: 1.12 per 10 mm Hg SBP drop; P = 0.006), and 180-day cardiovascular death (HR: 1.09 per 10 mm Hg SBP drop; P = 0.026) after adjustment for potential confounders including baseline SBP. There was no interaction between the prognostic value of early SBP drop according to the presence or absence of WRF. CONCLUSIONS In patients hospitalized for AHF, a greater early drop in SBP was associated with a higher incidence of WRF, worsening heart failure, and an increased risk for 180-day cardiovascular death. However, the association between SBP drop and prognosis was not influenced by WRF. (Efficacy, Safety and Tolerability of Serelaxin When Added to Standard Therapy in AHF [RELAX-AHF-2]; NCT01870778) (J Am Coll Cardiol HF 2021;9:890-903) (c) 2021 by the American College of Cardiology Foundation

Prevalence of postural hypotension in patients with treated hypertension

Wstęp Uważa się, że do występowania ortostatycznych spadków ciśnienia tętniczego (OH) predysponują nadciśnienie tętnicze, terapia hipotensyjna oraz podeszły wiek badanych. Celem niniejszej pracy było ustalenie związku między częstością OH a wiekiem, płcią, BMI, otyłością brzuszną i glikemią u pacjentów z nadciśnieniem tętniczym. Materiał i metody Badaniami objęto 250 osób (125 kobiet i 125 mężczyzn) z nadciśnieniem tętniczym w wywiadzie. Ciśnienie tętnicze mierzono w pozycji siedzącej i stojącej po 1 minucie pionizacji. Analizowano częstość spadku skurczowego ciśnienia tętniczego (SBP) o 20 i 10 mm Hg. Wyniki Spadek ciśnienia tętniczego po pionizacji nie zależał od wieku, płci, stopnia i rodzaju otyłości oraz od obecności zaburzeń gospodarki węglowodanowej. Spadek SBP o 10 mm Hg występował znamiennie częściej w grupie chorych powyżej 60 rż. oraz w grupie z BMI powyżej 30 kg/m2. Zaobserwowano tendencję do częstszego występowania spadku SBP o 10 mm Hg w grupie z otyłością brzuszną i zaburzeniami tolerancji glukozy. Nie stwierdzono innych zależności między spadkiem ciśnienia tętniczego po pionizacji a badanymi zmiennymi. Wnioski 1. Kryterium spadku SBP o 20 mm Hg wydaje się zbyt mało czułym wskaźnikiem rozpoznania OH u chorych z nadciśnieniem tętniczym. 2. Przy zastosowaniu kryterium spadku SBP o 10 mm Hg zaobserwowano znamienny wpływ wieku i BMI, ale nie otyłości brzusznej, na częstość OH. 3. Wydaje się, że OH u chorych z leczonym nadciśnieniem tętniczym nie jest już tak częstym problemem klinicznym jak podaje dotychczasowe piśmiennictwo. Można przypuszczać, iż jest to efektem stosowania leków o korzystniejszym profilu farmakokinetycznym.Background The presence of hypertension, antihypertensive therapy and elderly age are well known as common causes of orthostatic hypotension. The aim of the study was to evaluate the relationship between postural hypotension and age, gender, BMI, visceral obesity and glucose tolerance in hypertensive patients. Material and methods A total of 250 patients (125 females and 125 males) with history of hypertension were recruited for the study. The collected data included standing and supine blood pressure measurements, glucose level, BMI and waist circumference. The data were analyzed using criteria of 20 mm Hg and 10 mm Hg SBP decreases in response to standing. Results Mean blood pressure decrease did not depend on age, sex, BMI, presence of visceral obesity or glucose level. SBP pressure decrease of 10 mm Hg was more prevalent in older (> 60 yrs) and obese (BMI > 30 kg/m2) patients. There was a trend towards the correlation of 10 mm Hg SBP decrease with visceral obesity and impaired glucose levels. There were no other statistically significant correlation between PH and investigated variables. Conclusions 1. SBP decrease of 20 mm Hg is not sensitive enough to diagnose postural hypotension among patients with hypertension. 2. Prevalence of 10 mm Hg SBP decrease in response to standing is related to age and BMI, but not to visceral obesity or to blood glucose level. 3. Prevalence of orthostatic hypotension in the present study was less common than that suggested by earlier studies. This might be attributed to more favorable farmacokinetic profile of newer anti-hypertensive drugs

High blood pressure and intraocular pressure: a Mendelian randomization study

Purpose: To test for causality with regard to the association between blood pressure (BP) and intraocular pressure (IOP) and glaucoma. Methods: Single nucleotide polymorphisms (SNPs) associated with BP were identified in a genome-wide association study (GWAS) meta-analysis of 526,001 participants of European ancestry. These SNPs were used to assess the BP versus IOP relationship in a distinct sample (n = 70,832) whose corneal-compensated IOP (IOPcc) was measured. To evaluate the BP versus primary open-angle glaucoma (POAG) relationship, additional Mendelian randomization (MR) analyses were conducted using published GWAS summary statistics. Results: Observational analysis revealed a linear relationship between BP traits and IOPcc, with a +0.28 mm Hg increase in IOPcc per 10-mm Hg increase in systolic BP (95% confidence interval [CI], 0.26–0.29); for diastolic blood pressure (DBP) and pulse pressure (PP), these estimates were +0.41 mm Hg and +0.36 mm Hg, respectively. An inverse-variance weighted MR analysis did not support a causal relationship, as the estimated causal effect was +0.01 mm Hg IOPcc per 10-mm Hg increase in systolic blood pressure (SBP); +0.13 mm Hg IOPcc per 10-mm Hg increase in DBP; and +0.02 mm Hg IOPcc per 10-mm Hg increase in PP (all P > 0.05). With regard to the risk of POAG, MR analyse yielded causal effect estimate of odds ratio = 0.98 (95% CI, 0.92–1.04) per 10-mm Hg increase in SBP. Neither DBP nor PP demonstrated evidence of a causal effect on POAG. Conclusions: A range of different MR analysis methods provided evidence, in general, that the causal effect of BP on IOP (and POAG) was modest, or even zero. However, interpretation was complicated by SNPs associated with BP potentially having pleiotropic effects on IOP

Perkutana transluminalna angioplastika aortne rekoarktacije

Two cases of successful dilatation of recoarctation of the aorta due to a subclavien turndown operation are reported. In both cases Grüntzig technique was used. The first patient, aged 10 months, had the gradient rediced from 40 mm Hg to 10 mm Hg. The second, aged 1 year, had the gradient reduced from 80 mm Hg to 30 mm Hg. In the second patient right femoral pulse disapeared after procedure and surgery (thrombarteriectomy) was performed

What is the best treatment for hypertension in African Americans?

In African Americans with hypertension, therapy is best initiated with the low-sodium Dietary Approaches to Stop Hypertension (DASH) diet and a thiazide-type diuretic (strength of recommendation [SOR]: A, based on randomized controlled trials). If the blood pressure goal is not achieved with thiazide monotherapy, a calcium channel blocker, angiotensin-converting enzyme (ACE) inhibitor, angiotensin II receptor blocker (ARB), or a beta-blocker can be added. An initial combination treatment is recommended for patients with systolic blood pressure >15 mm Hg or diastolic blood pressure >10 mm Hg above target (SOR: C, expert opinion)

Mechanisms of hypertension during and after orthotopic liver transplantation in children

The aim of this study was to assess the hormonal alterations that may mediate the systemic hypertension that develops in patients during the perioperative period of orthotopic liver transplantation. We studied nine pediatric patients without previous hypertension or renal disease during six time points, starting before transplantation and ending at 48 hours after surgery. Hypertension developed in all patients in association with central venous pressures <10 mm Hg. Free water clearance was negative in all nine patients. Vasopressin levels increased intraoperatively but fell as hypertension developed. Atrial natriuretic factor levels increased as systemic blood pressure rose. A high level of plasma renin activity was observed in four patients with renal insufficiency. In six patients, postoperative 24-hour urinary norepinephrine excretion was within the normal age-adjusted range. These findings suggest that the combination of cyclosporine, corticosteroids, and, in some patients, an elevated plasma renin activity prevents the kidney from responding to the acute volume and salt overload with an appropriate diuresis and natriuresis, thus leading to systemic hypertension. The treatment of hypertension after liver transplantation may include salt restriction, diuretics, and, in those patients with a low creatinine excretion index, anglotensin coverting enzyme inhibitors. © 1989 The C. V. Mosby Company

Aqueous Angiography with Fluorescein and Indocyanine Green in Bovine Eyes.

PurposeWe characterize aqueous angiography as a real-time aqueous humor outflow imaging (AHO) modality in cow eyes with two tracers of different molecular characteristics.MethodsCow enucleated eyes (n = 31) were obtained and perfused with balanced salt solution via a Lewicky AC maintainer through a 1-mm side-port. Fluorescein (2.5%) or indocyanine green (ICG; 0.4%) were introduced intracamerally at 10 mm Hg individually or sequentially. With an angiographer, infrared and fluorescent images were acquired. Concurrent anterior segment optical coherence tomography (OCT) was performed, and fixable fluorescent dextrans were introduced into the eye for histologic analysis of angiographically positive and negative areas.ResultsAqueous angiography in cow eyes with fluorescein and ICG yielded high-quality images with segmental patterns. Over time, ICG maintained a better intraluminal presence. Angiographically positive, but not negative, areas demonstrated intrascleral lumens with anterior segment OCT. Aqueous angiography with fluorescent dextrans led to their trapping in AHO pathways. Sequential aqueous angiography with ICG followed by fluorescein in cow eyes demonstrated similar patterns.ConclusionsAqueous angiography in model cow eyes demonstrated segmental angiographic outflow patterns with either fluorescein or ICG as a tracer.Translational relevanceFurther characterization of segmental AHO with aqueous angiography may allow for intelligent placement of trabecular bypass minimally invasive glaucoma surgeries for improved surgical results

J-shaped relation between change in diastolic blood pressure and progression of aortic atherosclerosis

The J-shaped relation between diastolic blood pressure and mortality from coronary heart disease continues to provoke controversy. We examined the association between diastolic blood pressure and progression of aortic atherosclerosis in a population-based cohort of 855 women, aged 45-64 years at baseline. The women were examined radiographically for calcified deposits in the abdominal aorta, which have been shown to reflect intimal atherosclerosis. After 9 years of follow-up, slight progression of atherosclerosis was noted in 19% of women and substantial progression in 16%. The age-adjusted relative risk of substantial atherosclerotic progression in women with a decrease in diastolic pressure of 10 mm Hg or more was 2·5 (95% CI 1·3-5·6), compared with the reference group of women who had a smaller decrease or no change. The excess risk in this group was confined to women whose increase in pulse pressure was above the median (3·9 [1·5-9·9] vs 1·1 [0 3-4·2] in women with an increase in pulse pressure below the median). The relative risks for women with rises in diastolic pressure of 1-9 mm Hg and 10 mm Hg or more were 2·2 (1 1-4 3) and 3·5 (1 6-8 0), respectively. These findings suggest that a decline in diastolic blood pressure indicates vessel wall stiffening associated with atherosclerotic progression. They support the hypothesis that in low-risk subjects progression of atherosclerosis may be accompanied by a decrease in diastolic blood pressure rather than the opposing idea that low diastolic blood pressure precipitates the occurrence of atherosclerotic events