820 research outputs found
Monitoring serum insulin-like growth factor-I (IGF-I), IGF binding protein-3 (IGFBP-3), IGF-I/IGFBP-3 molar ratio and leptin during growth hormone treatment for disordered growth
OBJECTIVE: Serum IGF-I levels are monitored during
GH replacement treatment in adults with GH defi-
ciency (GHD) to guide GH dose adjustment and to
minimize occurrence of GH-related side-effects. This
is not routine practice in children treated with GH. The
aim of this study was to evaluate changes in (1) serum
IGF-I, IGFBP-3 and IGF-I/IGFBP-3 molar ratio, and (2)
serum leptin, an indirect marker of GH response,
during the first year of GH treatment in children with
disordered growth.
DESIGN: An observational prospective longitudinal
study with serial measurements at five time points
during the first year of GH treatment was carried out.
Each patient served as his/her own control.
PATIENTS The study included 31 patients, grouped
as (1) GHD (n=20) and (2) non-GHD (Turner syndrome
n=7; Noonan syndrome n=4), who had not previously
received GH treatment.
MEASUREMENTS: Serum IGF-I, IGFBP-3 and leptin
levels were measured before treatment and after
6 weeks, 3 months, 6 months and 12 months of GH
treatment, with a mean dose of 0.5 IU/kg/wk in GHD
and 0.7 IU/kg/wk in non-GHD groups. IGF-I, IGFBP-3
and the calculated IGF-I/IGFBP-3 molar ratio were
expressed as SD scores using reference values from
the local population.
RESULTS: In the GHD group, IGF-I SDS before treatment was lower compared with the non-GHD (-5.4 ± 2.5 vs. -1.8 ± 1.0; P < 0.001). IGF-I (-1.8 SDS ± 2.2) and IGFBP-3 (-1.1 SDS ± 0.6) levels and their molar ratios were highest at 6 weeks and remained relatively constant thereafter. In the non-GHD group, IGF-I levels increased throughout the year and were maximum at 12 months (0.3 SDS ± 1.4) while IGFBP-3 (1.1 SDS ± 0.9) and IGF-I/IGFBP-3 molar ratio peaked at 6 months. In both groups, IGF-I SDS and IGF-I/IGFBP-3 during treatment correlated with the dose of GH expressed as IU/m2/week (r-values 0.77 to 0.89; P = 0.005) but not as IU/kg/week. Serum leptin levels decreased significantly during GH treatment in the GHD (median before treatment 4.0 g/l; median after 12 months treatment 2.4 g/l; P = 0.02) but not the non-GHD (median before treatment 3.0 g/l; median after 12 months treatment 2.6 g/l). In the GHD group, serum leptin before treatment correlated with 12 month change in height SDS (r = 0.70, P = 0.02).
CONCLUSIONS: The pattern of IGF-I, IGFBP-3 and
their molar ratio during the first year of GH treatment
differed between the GHD and non-GHD groups. Calculation
of GH dose by surface area may be preferable
to calculating by body weight. As a GH dose-dependent
increase in serum IGF-I and IGF-I/IGFBP-3 may
be associated with adverse effects, serum IGF-I and
IGFBP-3 should be monitored routinely during longterm
GH treatment. Serum leptin was the only variable
that correlated with first year growth response in
GHD
A study of one class of NLP problems arising in parametric Semi-Infinite Programming
The paper deals with a nonlinear programming (NLP) problem that depends on a finite number of integers (parameters). This problem has a special form, and arises as an auxiliary problem in study of solutions' properties of parametric semi-infinite programming (SIP) problems with finitely representable compact index sets. Therefore, it is important to provide a deep study of this NLP problem and its properties w.r.t. the values of the parameters. We are especially interested in the case when optimal solutions of the NLP problem satisfy certain properties due to some specific requirements arising in parametric SIP. We establish the values of the parameters for which optimal solutions of the corresponding NLP problem fulfil the needed properties, and suggest an algorithm that determines the right values of the parameters. An example is proposed to illustrate the application of the algorithm
Optimal low-thrust trajectories to asteroids through an algorithm based on differential dynamic programming
In this paper an optimisation algorithm based on Differential Dynamic Programming is applied to the design of rendezvous and fly-by trajectories to near Earth objects. Differential dynamic programming is a successive approximation technique that computes a feedback control law in correspondence of a fixed number of decision times. In this way the high dimensional problem characteristic of low-thrust optimisation is reduced into a series of small dimensional problems. The proposed method exploits the stage-wise approach to incorporate an adaptive refinement of the discretisation mesh within the optimisation process. A particular interpolation technique was used to preserve the feedback nature of the control law, thus improving robustness against some approximation errors introduced during the adaptation process. The algorithm implements global variations of the control law, which ensure a further increase in robustness. The results presented show how the proposed approach is capable of fully exploiting the multi-body dynamics of the problem; in fact, in one of the study cases, a fly-by of the Earth is scheduled, which was not included in the first guess solution
Histology of portal vascular changes associated with idiopathic non-cirrhotic portal hypertension: nomenclature and definition.
Idiopathic non-cirrhotic portal hypertension (INCPH) is a rare vascular liver disease that has attracted new interest in recent years. It is characterised by clinical signs of portal hypertension in the absence of cirrhosis or severe fibrosis and any known cause of portal hypertension. As much uncertainty exists about INCPH pathophysiology, and no definite diagnostic tests are available, liver biopsy is an essential tool for achieving a definite diagnosis. Unfortunately, the histological diagnosis of INCPH is not always straightforward, as the characteristic lesions are unevenly distributed, vary greatly in their severity, are often very subtle, and are not all necessarily present in a single case. Furthermore, specifically for the characteristic portal vessel changes observed in INCPH, the terminology and definition are ambiguous, which adds complexity to the already complex clinicopathological scenario. An international study group of liver pathologists and hepatologists pursued a consensus on nomenclature for the portal vascular lesions of INCPH. Such standardisation may assist pathologists in the recognition of such lesions, and will possibly facilitate further advancement in this field
A weakly stable algorithm for general Toeplitz systems
We show that a fast algorithm for the QR factorization of a Toeplitz or
Hankel matrix A is weakly stable in the sense that R^T.R is close to A^T.A.
Thus, when the algorithm is used to solve the semi-normal equations R^T.Rx =
A^Tb, we obtain a weakly stable method for the solution of a nonsingular
Toeplitz or Hankel linear system Ax = b. The algorithm also applies to the
solution of the full-rank Toeplitz or Hankel least squares problem.Comment: 17 pages. An old Technical Report with postscript added. For further
details, see http://wwwmaths.anu.edu.au/~brent/pub/pub143.htm
Optimal Flying Wings: A Numerical Optimization Study
Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/97067/1/AIAA2012-1758.pd
A Scalable Parallel Approach for High-Fidelity Aerostructural Analysis and Optimization
Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/97076/1/AIAA2012-1922.pd
Oracle-based optimization applied to climate model calibration
In this paper, we show how oracle-based optimization can be effectively used for the calibration of an intermediate complexity climate model. In a fully developed example, we estimate the 12 principal parameters of the C-GOLDSTEIN climate model by using an oracle- based optimization tool, Proximal-ACCPM. The oracle is a procedure that finds, for each query point, a value for the goodness-of-fit function and an evaluation of its gradient. The difficulty in the model calibration problem stems from the need to undertake costly calculations for each simulation and also from the fact that the error function used to assess the goodness-of-fit is not convex. The method converges to a Fbest fit_ estimate over 10 times faster than a comparable test using the ensemble Kalman filter. The approach is simple to implement and potentially useful in calibrating computationally demanding models based on temporal integration (simulation), for which functional derivative information is not readily available
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