Shock loss measurements in non-ideal supersonic flows of organic vapors.

This paper presents the first ever direct measurements of total pressure losses across shocks in supersonic flows of organic vapors in non-ideal conditions, so in the thermodynamic region close to the liquid-vapor saturation curve and the critical point where the ideal gas law is not applicable. Experiments were carried out with fluid siloxane MM (hexamethyldisiloxane, C 6 H 18 OSi 2 ), commonly employed in medium-/high-temperature organic Rankine cycles (ORCs), in the Test Rig for Organic VApors (TROVA), a blowdown wind tunnel at the Laboratory of Compressible fluid dynamics for Renewable Energy Applications (CREA lab) of Politecnico di Milano. A total pressure probe was inserted in superheated MM vapor flow at Mach number ∼ 1.5 with total conditions in the range 215 - 230 ∘ C and 2 - 12 bar at varying levels of non-ideality, with a compressibility factor evaluated at total conditions between Z T = 0.68 - 0.98 . These operating conditions are representative of the first-stage stator of ORC turbines. Measured shock losses were compared with those calculated from pre-shock quantities by solving conservation equations across a normal shock, with differences always below 2 % attesting a satisfactory reliability of the implemented experimental procedure. An in-depth analysis was then carried out, highlighting the direct effects of non-ideality on shock intensity. Even at the mildly non-ideal conditions with Z T ≳ 0.70 considered here, non-ideality was responsible for a significantly stronger shock compared to the ideal gas limit at same pre-shock Mach number, with differences as large as 6 % .

Thyroid function and morphology in subjects with microdeletion of chromosome 22q11 (del(22)(q11)).

INTRODUCTION: Monoallelic microdeletion of chromosome 22q11 (22q11DS) is considered to be the commonest human microdeletion syndrome. Abnormalities of thyroid function are sporadically reported in this syndrome, but very few studies have specifically assessed this issue, and thyroid morphology has not been systematically studied. DESIGN: To evaluate the prevalence of abnormalities of thyroid function and morphology in a cohort of paediatric and adult patients with 22q11DS. METHODS: Thirty patients with 22q11DS (median age 9.7, range 1.5-43.9 years) were studied. In all subjects, serum free-T(3), free-T(4), TSH, thyroperoxidase, thyroglobulin, and TSHr auto-antibodies, as well as thyroid ultrasonographic data, were evaluated and compared with age- and sex-matched healthy control groups, for paediatric and adult patients. RESULTS: Fourteen (46.6%) patients showed thyroid hypoplasia involving the entire gland. In all the patients, the volume of the left lobe of the thyroid was significantly reduced (P < 0.01). Among the subjects with thyroid hypoplasia, 10 out of 14 (71%) showed a concomitant heart malformation, a condition that was present in five (31%) of the subjects with a normal thyroid volume (P < 0.05). Seven (23.3%) cases of subclinical hypothyroidism and one (3.3%) case of overt hypothyroidism were identified. Three (10%) patients were positive for thyroid auto-antibodies. Of the patients with overt and subclinical hypothyroidism, five out of eight (62.5%) patients showed thyroid hypoplasia. CONCLUSIONS: This study confirms the presence of alterations of thyroid function in 22q11DS, and also suggests a frequent occurrence of abnormalities in thyroid morphology in these subjects. Patients with 22q11DS should be monitored for thyroid function, and thyroid ultrasound screening should be considered, especially in those patients with changes in thyroid function or congenital heart malformations. The possible relationship between developmental abnormalities in the heart and the thyroid gland should be confirmed.

Clinical efficacy and tolerability of linezolid in pediatric patients: a systematic review.

BACKGROUND: Linezolid is marketed for the treatment of severe, vancomycin-resistant infections with gram-positive bacteria in adults. Most information regarding the pharmacokinetic profile, efficacy, and tolerability of linezolid is derived from adult studies. OBJECTIVE: The aim of this review was to summarize evidence regarding the use of linezolid in infants and children, focusing on the drug's clinical efficacy data and tolerability profile. METHODS: A literature search was conducted of the Cochrane Library, EMBASE, and MEDLINE databases, from their inception through July 20, 2009, using the following terms: linezolid, newborn, infant, child, pediatrics, adolescent, human, clinical trial, and case report. Articles were excluded if they were redundant or not pertinent. (Articles that did not focus on the use of linezolid in children were considered not pertinent.) Bibliographies of all relevant articles were also evaluated. RESULTS: Forty-seven publications regarding the use of linezolid in children were included in the review: 5 pharmacokinetic studies, 32 case reports, 6 randomized clinical trials (RCTs), 2 uncontrolled trials, 1 subanalysis of 2 published RCTs, and 1 subanalysis of published data about linezolid's tolerability. Pharmacokinetic data on linezolid use in children were derived from studies that enrolled 447 children. Plasma pharmacokinetics of linezolid in pediatric patients were found to be age dependent. Results from 6 vancomycinor cefadroxil-controlled RCTs (including 1480 children) evaluating linezolid treatment in children reported variable clinical cure rates, ranging from 75.0% to 93.2% in children with skin and skin-structure infections and from 77.5% to 90.0% in children with bacteremia or pneumonia. No significant difference in clinical cure rates between the linezolid group and the comparator group was observed in any study. The most frequently reported adverse events were diarrhea (from 3.1% to 16.8%), nausea and/or vomiting (from 2.9% to 11.9%), and thrombocytopenia (from 1.9% to 4.7%). To date, 3 cases of neuropathy have been described in children. CONCLUSIONS: The reviewed pediatric studies in skin and skin-structure infections, bacteremia, or pneumonia found that linezolid was associated with high clinical cure rates (75.0%-93.2%) that did not differ significantly from those of vancomycin or cefadroxil. RCTs enrolling children with other types of infection (eg, osteomyelitis, endocarditis), as well as long-term studies, are needed to draw definitive conclusions about linezolid's efficacy and tolerability in pediatric patients. Careful monitoring for adverse events and possible linezolid resistance continues to be essential.

Bone density and metabolism in subjects with microdeletion of chromosome 22q11 (del22q11).

INTRODUCTION: Although hypoparathyroidism with hypocalcaemia is one of the most frequent clinical features of monoallelic microdeletion of chromosome 22q11 (22q11DS), bone mass and metabolism have not yet been assessed in these patients. DESIGN: This study aimed to evaluate bone mass and metabolism in a cohort of patients, both children and adults, with 22q11DS. METHODS: In twenty-eight patients with 22q11DS (median age 12.5, range 6.1-42.8 years), serum levels of ionised and total calcium, phosphate, parathyroid hormone (PTH), 25-hydroxyvitamin D, 1,25-dihydroxyvitamin D, osteocalcin and bone-specific alkaline phosphatase (BSAP), and urinary deoxypyridinoline concentrations were evaluated. In these patients, bone mineral density (BMD) was evaluated by dual-energy X-ray absorptiometry (DXA) examination, and volumetric BMD (bone mineral apparent density (BMAD)) was calculated. The data obtained from paediatric and adult patients were compared with two age-, sex- and body size-matched healthy subject control groups. RESULTS: Patients with 22q11DS showed a reduced BMAD Z-score compared with controls (P<0.001). These patients also had significantly lower ionised (P<0.001) and total calcium (P<0.05) levels as well as lower PTH levels (P<0.05), compared with the controls. In particular, children and young patients with 22q11DS had significantly lower serum osteocalcin levels (P<0.001), BSAP levels (P<0.001) and urinary deoxypyridinoline concentrations (P<0.001) than controls. These results were not confirmed in adults. Finally, patients with hypoparathyroidism and/or hypocalcaemia at the time of the study showed significantly lower ionised (P<0.001) and total calcium levels (P<0.001), PTH levels (P<0.05), BSAP levels (P<0.001), osteocalcin levels (P<0.001) and urinary deoxypyridinoline concentrations (P<0.001), compared with patients without hypoparathyroidism and/or hypocalcaemia. Nonetheless, the BMAD Z-score did not show substantial differences between these two groups. CONCLUSIONS: Subjects with 22q11DS have a significant reduction in bone mass that appears to be more severe in adults who have already attained peak bone mass than in children who are still growing. Therefore, we suggest a close monitoring of bone mass and metabolism in 22q11DS patients.