bluuebunny/crossref_metadata_2025 huggingface dataset:
Testing the Statistical Significance of Linear Programming Estimators
Authors: Horsky Dan , Nelson Paul
Published: February 2006

Linear programming–based estimation procedures are used in a variety of arenas. Two notable areas are multiattribute utility models (LINMAP) and production frontiers (data envelopment analysis (DEA)). Both LINMAP and DEA have theoretical and managerial advantages. For example, LINMAP treats ordinal-scaled preference data as such in uncovering individual-level attribute weights, while regression treats these preferences as interval scaled. DEA produces easy-to-understand efficiency measures, which allow for improved productivity benchmarking. However, acceptance of these techniques is hindered by the lack of statistical significance tests for their parameter estimates.

In this paper, we propose and evaluate such parameter significance tests. Two types of tests are forwarded. The first examines whether a model’s fit is significantly reduced when an explanatory variable is deleted. The second is based on generating a standard deviation or distribution for the parameter estimate using nonparametric jackknife or bootstrap techniques. We demonstrate through simulations that both types of tests reliably identify both significant and insignificant parameters. The availability of these tests, especially the relatively simple and easy-to-use tests of the first type, should enhance the utilization of linear programming–based estimation.
Pricing American-Style Derivatives with European Call Options
Authors: Laprise Scott B. , Fu Michael C. , Marcus Steven I. , Lim Andrew E. B. , Zhang Huiju
Published: February 2006

We present a new approach to pricing American-style derivatives that is applicable to any Markovian setting (i.e., not limited to geometric Brownian motion) for which European call-option prices are readily available. By approximating the value function with an appropriately chosen interpolation function, the pricing of an American-style derivative with arbitrary payoff function is converted to the pricing of a portfolio of European call options, leading to analytical expressions for those cases where analytical European call prices are available (e.g., the Merton jump-diffusion process). Furthermore, in many settings, the approach yields upper and lower analytical bounds that provably converge to the true option price. We provide computational results to illustrate the convergence and accuracy of the resulting estimators.
A Contract and Balancing Mechanism for Sharing Capacity in a Communication Network
Authors: Anderson Edward , Kelly Frank , Steinberg Richard
Published: February 2006

We propose a method for determining how much to charge users of a communication network when they share bandwidth. Our approach can be employed either when a network owner wishes to sell bandwidth for a specified period of time to a number of different users, or when users cooperate to build a network to be shared among themselves. Our proposed contract and balancing mechanism can mediate between rapidly fluctuating prices and the longer time scales over which bandwidth contracts may be traded. An advantage of the process is that it avoids perverse incentives for a capacity provider to increase congestion.
Uncertainty Aversion with Second-Order Utilities and Probabilities
Authors: Nau Robert F.
Published: February 2006

Subjective expected utility theory does not distinguish between attitudes toward uncertainty (ambiguous probabilities) and attitudes toward risk (unambiguous probabilities). Both are explained in terms of nonlinear utility for money rather than properties of events per se, hence, the decision maker displays the same attitude toward all sources of risk and uncertainty. There is ample evidence that real decision makers do not always behave (or even wish to behave) in this way, and instead they often distinguish between risk and uncertainty, as in Ellsberg’s (1961) paradox. This paper presents a simple axiomatic model of nonneutral attitudes toward uncertainty and a behavioral test for uncertainty aversion that is applicable even if utility is state dependent. The decision maker may display different degrees of aversion toward gambles on different kinds of events, e.g., being systematically more averse toward gambles on events whose probabilities are more ambiguous. For such a decision maker, the elicitation of preferences among objective gambles may not yield the correct measure of risk aversion for modeling real-world decisions.
Supplier Commitment and Production Decisions Under a Forecast-Commitment Contract
Authors: Durango-Cohen Elizabeth Junqueira , Yano Candace Arai
Published: February 2006

Manufacturing firms in capital-intensive industries face inherent demand volatility for their products and the inability to change their capacity quickly. To cope with these challenges, manufacturers often enter into contracts with their customers that offer greater certainty of supply in return for more predictable orders. In this paper, we study a “forecast-commitment” contract in which the customer provides a forecast, the supplier makes a production commitment to the customer based on the forecast, and the customer’s minimum order quantity is a function of the forecast and committed quantities. We provide a complete analysis of the supplier’s decisions when there is a single customer facing uncertain demand. We first show that the supplier has two dominant commitment strategies: committing to the forecast or committing to the production quantity. We then characterize the jointly optimal commitment and production strategy for the supplier and extend the results to consider a capacity constraint. We show that the proposed contract can moderate the supplier’s motivation to underproduce, and due to the structure of the contract and the form of the supplier’s optimal strategy, also limits the customer’s incentive to overforecast. We also provide results for a capacitated two-customer example, which show that the supplier’s choice of production quantity for each customer is not necessarily nondecreasing in the total available capacity.
Dynamic Pricing Through Discounts for Optimizing Multiple-Class Demand Fulfillment
Authors: Ding Qing , Kouvelis Panos , Milner Joseph M.
Published: February 2006

In a multiple-customer-class model of demand fulfillment for a single item, we consider the use of dynamic price discounts to encourage backlogging of demand for customer classes denied immediate service. Customers are assumed to arrive over several stages in a period, and customer classes are distinguished by their contractual price and sensitivity to discounts. Through dynamic programming we determine the optimal discounts to offer, assuming a linear model for the sensitivity of customers to such inducements. We show that customers are served in class order, and allocation of inventory to demand is determined by considering the current number of customers backlogged, as well as the current inventory position. Through comparison to a naive supplier allocating inventory first come/first served with no discounting, we show that profits are primarily influenced by the allocation of capacity, and the use of price discounts primarily benefits the second-class customers’ overall fill rate. Heuristics for implementation of the solution in real-time settings are given.
Supracondylar humeral fractures in children
Authors: Mangwani J. , Nadarajah R. , Paterson J. M. H.
Published: February 2006

Although supracondylar fracture is a very common elbow injury in childhood, there is no consensus on the timing of surgery, approach for open reduction and positioning of fixation wires. We report our ten-year experience between 1993 and 2003 in 291 children.

Most fractures (285; 98%) were extension injuries, mainly Gartland types II (73; 25%) and III (163; 56%). Six (2%) were open fractures and a neurovascular deficit was seen in 12 (4%) patients. Of the 236 children (81%) who required an operation, 181 (77%) were taken to theatre on the day of admission. Most (177; 75%) of the operations were performed by specialist registrars. Fixation was by crossed Kirschner wires in 158 of 186 (85%) patients and open reduction was necessary in 52 (22%).

A post-operative neurological deficit was seen in nine patients (4%) and three (1%) required exploration of the ulnar nerve. Only 22 (4%) patients had a long-term deformity, nine (3%) from malreduction and three (1%) because of growth arrest, but corrective surgery for functional limitation was required in only three (1%) patients.
Multiple skeletal metastases from a giant cell tumour of the distal fibula with fatal outcome
Authors: Leichtle C. I. , Leichtle U. G. , Gärtner V. , Schimmel H. , Hartmann J. T. , Rudert M.
Published: February 2006

A giant cell tumour is a primary lesion of bone of intermediate severity. Its histogenesis is unclear. In a few cases pulmonary metastases have been described. Multiple skeletal metastases in the absence of sarcomatous change have been observed.

We present a case report of a 25-year-old woman with a recurrent giant cell tumour of the distal fibula. After a second recurrence and six years after the initial diagnosis, she rapidly developed multiple bony metastases. The outcome was fatal.
One- or two-stage bilateral total hip arthroplasty
Authors: Bhan S. , Pankaj A. , Malhotra R.
Published: February 2006

We compared the safety and outcome of one-stage bilateral total hip arthroplasty with those of a two-stage procedure during different admissions in a prospective, randomised controlled trial in an Asian population. Of 168 patients included in the study, 83 had a single- and 85 a two-stage procedure. Most of the patients (59.9%) suffered from inflammatory arthritis.

The intra-operative complications, early systemic complications, the operating time, positioning of the components, the functional score, restoration of limb length and survival rates at 96 months were similar in the two groups. The total estimated blood loss was significantly lower in patients undergoing a one-stage procedure than in patients who had a two-stage procedure, but the transfusion requirements were significantly higher in the former group (p = 0.001). The hospital stay was significantly shorter in the one-stage group, 7.25 days (sd 1.30; 5 to 20) compared with 10 days (sd 1.65; 8 to 24) in the two-stage group (p = 0.023). We believe that a one-stage procedure is safe and appropriate in our population.
The Kent hip prosthesis
Authors: Sexton S. A. , Stossel C. A. , Haddad F. S.
Published: February 2006

The Kent hip is a distally-locked femoral stem which was developed to address severe proximal bone loss, severe bony deformity and peri-prosthetic fracture.

We reviewed the results of 145 consecutive Kent hips implanted into 141 patients between 1987 and 2000. The indications for implantation were aseptic loosening (75 hips), septic loosening (two), peri-prosthetic and prosthetic fracture (37), severe bony deformity (24), and fracture through a proximal femoral metastasis (seven).

The median time to full weight-bearing after surgery was two days and the mean length of follow-up was 5.1 years (2 to 15). Further revisions were required for 13 femoral stems. With removal of the stem for any reason as an end-point, the cumulative survival at five, ten and 15 years was 93%, 89% and 77%, respectively. In patients aged ≥ 70 years, the cumulative survival at 15 years was 92%, compared with 68% in those aged < 70 years. Because of these findings, we recommend the use of interlocking stems in patients aged ≥ 70 years, particularly in those with a peri-prosthetic fracture, for whom alternative methods are limited. Outcome scores and survival data, compared with other systems, indicate that the Kent hip should be used with caution in younger patients.
Elastic stable intramedullary nail fixation for severely displaced fractures of the neck of the radius in children
Authors: Prathapkumar K. R. , Garg N. K. , Bruce C. E.
Published: February 2006

Several techniques are available for the treatment of displaced fractures of the neck of the radius in children. We report our experience in 14 children treated by indirect reduction and fixation using an elastic stable intramedullary nail. The patients were followed up for a mean of 28 months. One developed asymptomatic avascular necrosis. The rest had excellent results. One had a neuropraxia of the posterior interosseous nerve, which recovered within six weeks. We advocate elastic stable intramedullary nailing for the closed reduction and fixation of these fractures in children.
Management of severe open tibial fractures
Authors: Naique S. B. , Pearse M. , Nanchahal J.
Published: February 2006

Although it is widely accepted that grade IIIB open tibial fractures require combined specialised orthopaedic and plastic surgery, the majority of patients in the UK initially present to local hospitals without access to specialised trauma facilities. The aim of this study was to compare the outcome of patients presenting directly to a specialist centre (primary group) with that of patients initially managed at local centres (tertiary group).

We reviewed 73 consecutive grade IIIB open tibial shaft fractures with a mean follow-up of 14 months (8 to 48). There were 26 fractures in the primary and 47 in the tertiary group. The initial skeletal fixation required revision in 22 (47%) of the tertiary patients. Although there was no statistically-significant relationship between flap timing and flap failure, all the failures (6 of 63; 9.5%) occurred in the tertiary group. The overall mean time to union of 28 weeks was not influenced by the type of skeletal fixation. Deep infection occurred in 8.5% of patients, but there were no persistently infected fractures. The infection rate was not increased in those patients debrided more than six hours after injury.

The limb salvage rate was 93%. The mean limb functional score was 74% of that of the normal limb. At review, 67% of patients had returned to employment, with a further 10% considering a return after rehabilitation. The times to union, infection rates and Enneking limb reconstruction scores were not statistically different between the primary and tertiary groups.

The increased complications and revision surgery encountered in the tertiary group suggest that severe open tibial fractures should be referred directly to specialist centres for simultaneous combined management by orthopaedic and plastic surgeons.
Infection in knee replacements after previous injection of intra-articular steroid
Authors: Papavasiliou A. V. , Isaac D. L. , Marimuthu R. , Skyrme A. , Armitage A.
Published: February 2006

We reviewed 231 patients who had undergone total knee replacement with an AGC (Biomet) implant over a period of 2.5 years. After applying exclusion criteria and with some loss to follow-up, there were 144 patients available for study. These were divided into two groups; those who had received intra-articular steroid in the 11 months before surgery and those who had not.

There were three deep infections, all of which occurred in patients who had received a steroid injection. The incidence of superficial infection was not significantly different in the two groups. Five patients had undergone investigation for suspected deep infection because of persistent swelling or pain and all of these had received an intra-articular injection pre-operatively. We conclude that the decision to administer intra-articular steroids to a patient who may be a candidate for total knee replacement should not be taken lightly because of a risk of post-operative deep infection.
Early versus delayed treatment of extension type-3 supracondylar fractures of the humerus in children
Authors: Sibinski M. , Sharma H. , Bennet G. C.
Published: February 2006

We examined differences in the rate of open reduction, operating time, length of hospital stay and outcome between two groups of children with displaced supracondylar fractures of the humerus who underwent surgery either within 12 hours of the injury or later.

There were 77 children with type-3 supracondylar fractures. Of these, in 43 the fracture was reduced and pinned within 12 hours and in 34 more than 12 hours after injury. Both groups were similar in regard to gender, age and length of follow-up. Bivariate and logistical regression analysis showed no statistical difference between the groups. The number of peri-operative complications was low and did not affect the outcome regardless of the timing of treatment.

Our study confirmed that the treatment of uncomplicated displaced supracondylar fractures of the humerus can be early or delayed. In these circumstances operations at night can be avoided.
Correlation of clinical and ultrasonographic findings after Achilles tenotomy in idiopathic club foot
Authors: Barker S. L. , Lavy C. B. D.
Published: February 2006

Achilles tenotomy is a recognised step in the Ponseti technique for the correction of idiopathic congenital talipes equinovarus in most percutaneous cases. Its use has been limited in part by concern that the subsequent natural history of the tendon is unknown. In a study of 11 tendons in eight infants, eight tendons were shown to be clinically intact and ten had ultrasonographic evidence of continuity three weeks after tenotomy. At six weeks after tenotomy all tendons had both clinical and ultrasonographic evidence of continuity.
Heparin-induced thrombocytopenia
Authors: Kejariwal D.
Published: February 2006

Heparin is a drug widely used for thromboprophylaxis or treatment in many clinical situations. However, it can cause serious adverse effects, including thrombocytopenia, which is a potentially life-threatening condition. Unfortunately, heparin-induced thrombocytopenia is generally under-recognised and under-diagnosed. A case of heparin-induced thrombocytopenia occurring in a post-operative orthopaedic patient in association with prophylactic low-molecular-weight heparin is described.
Detection of Mucopolysaccharidosis Type II by Measurement of Iduronate-2-Sulfatase in Dried Blood Spots and Plasma Samples
Authors: Dean Caroline J , Bockmann Michelle R , Hopwood John J , Brooks Doug A , Meikle Peter J
Published: February 2006

Background: Mucopolysaccharidosis type II (MPS II) is a lysosomal storage disorder related to a deficiency in the enzyme iduronate-2-sulfatase (IDS). Clinical trials of enzyme replacement therapy are in progress, but effective treatment will require screening assays to enable early detection and diagnosis of MPS II. Our study evaluated the diagnostic accuracy of IDS protein and enzyme activity measurements in dried blood spots and plasma.

Methods: We collected dried-blood-spot and plasma samples from unaffected control individuals and from MPS II patients. We measured IDS protein concentration with a 2-step time-delayed dissociation-enhanced lanthanide fluorescence immunoassay. To measure enzyme activity, we immobilized anti-IDS antibody on microtiter plates to capture the enzyme and measured its activity with the fluorogenic substrate 4-methylumbelliferyl sulfate.

Results: Dried-blood-spot samples from MPS II patients showed an almost total absence of IDS activity (0–0.075 μmol · h−1 · L−1) compared with control blood spots (0.5–4.7 μmol · h−1 · L−1) and control plasma (0.17–8.1 μmol · h−1 · L−1). A dried-blood-spot sample from only 1 of 12 MPS II patients had detectable concentrations of IDS protein (24.8 μg/L), but no IDS protein was detected in plasma from MPS II patients. Ranges for IDS protein in control samples were 25.8–153 μg/L for blood spots and 22.8–349.4 μg/L for plasma.

Conclusion: Measurement of the IDS protein concentration and enzyme activity (as measured by a simple fluorogenic assay with an immune capture technique) enables identification of the majority of MPS II patient samples from both dried blood spots and plasma samples.
Anesthesia Alarms in Context: An Observational Study
Authors: Seagull F. Jacob , Sanderson Penelope M.
Published: February 2006

This paper surveys current work on the design of alarms for anesthesia environments and notes some of the problems arising from the need to interpret alarms in context. Anesthetists' responses to audible alarms in the operating room were observed across four types of surgical procedure (laparoscopic, arthroscopic, cardiac, and intracranial) and across three phases of a procedure (induction, maintenance, and emergence). Alarms were classified as (a) requiring a corrective response, (b) being the intended result of a decision, (c) being ignored as a nuisance alarm, or (d) functioning as a reminder. Results revealed strong effects of the type of procedure and phase of procedure on the number and rate of audible alarms. Some alarms were relatively confined to specific phases; others were seen across phases, and responses differed according to phase. These results were interpreted in light of their significance for the development of effective alarm systems. Actual or potential applications of this research include the design of alarm systems that are more informative and more sensitive to operative context than are current systems.
Does Stress Training Generalize to Novel Settings?
Authors: Driskell James E. , Johnston Joan Hall , Salas Eduardo
Published: February 2006

Many high-stress task environments are complex and dynamic, and it is often difficult during training to anticipate the exact conditions that may be encountered in these settings. We conducted an empirical study to examine whether the positive effects of stress training that addressed one specific type of stressor and task would remain when trainees performed under a novel stressor or performed a novel task. Participants performed a laboratory task under stress conditions. Measures of task performance and self-reported stress were obtained at three performance trials: (a) prior to stress training, (b) after a stress training intervention targeted to that specific task environment, and (c) under novel stressor/task conditions. Results indicated that the beneficial effects of stress training were retained when participants performed under a novel stressor and performed a novel task. We discuss the implications of this study with regard to their application in the design of stress training and the transfer of learning to complex, dynamic task environments.
Peripheral Visual Feedback: A Powerful Means of Supporting Effective Attention Allocation in Event-Driven, Data-Rich Environments
Authors: Nikolic Mark I. , Sarter Nadine B.
Published: February 2006

Breakdowns in human-automation coordination in data-rich, event-driven domains such as aviation can be explained in part by a mismatch between the high degree of autonomy yet low observability of modern technology. To some extent, the latter is the result of an increasing reliance in feedback design on foveal vision - an approach that fails to support pilots in tracking system-induced changes and events in parallel with performing concurrent flight-related tasks. One possible solution to the problem is the distribution of tasks and information across sensory modalities and processing channels. A simulator study is presented that compared the effectiveness of current foveal feedback and two implementations of peripheral visual feedback for keeping pilots informed about un commanded changes in the status of an automated cockpit system. Both peripheral visual displays resulted in higher detection rates and faster response times, without interfering with the performance of concurrent visual tasks any more than does currently available automation feedback. Potential applications include improved display designs that support effective attention allocation in a variety of complex dynamic environments, such as aviation, process control, and medicine.
The Use of 2D and 3D Displays for Shape-Understanding versus Relative-Position Tasks
Authors: St. John Mark , Cowen Michael B. , Smallman Harvey S. , Oonk Heather M.
Published: February 2006

Research on when and how to use three-dimensional (3D) perspective views on flat screens for operational tasks such as air traffic control is complex. We propose a functional distinction between tasks: those that require shape understanding versus those that require precise judgments of relative position. The distortions inherent in 3D displays hamper judging relative positions, whereas the integration of dimensions in 3D displays facilitates shape understanding. We confirmed these hypotheses with two initial experiments involving simple block shapes. The shape-understanding tasks were identification or mental rotation. The relative-position tasks were locating shadows and determining directions and distances between objects. We then extended the results to four experiments involving complex natural terrain. We compare our distinction with the integral/separable task distinction of Haskel and Wickens (1993). Applications for this research include displays for air traffic control, geoplots for military command and control, and potentially, any display of 3D information.
Air-stable Co-, Fe-, and Fe/Co-Nanoparticles and Ferrofluids
Authors: Behrens Silke , Bönnemann Helmut , Matoussevitch Nina , Dinjus Eckhard , Modrow Hartwig , Palina Natalie , Frerichs Martin , Kempter Volker , Maus-Friedrichs Wolfgang , Heinemann André , Kammel Martin , Wiedenmann Albrecht
Published: February 2006

Air-stable Co, Fe, and Fe/Co nanoparticles are accessible by thermolysis of the metal carbonyl precursors in the presence of aluminium alkyls and subsequent “smooth oxidation”. The structure of the particles was investigated by transmission electron microscopy (TEM, HRTEM), X-ray absorption spectroscopy (XAS), X-ray and ultraviolet photoelectron spectroscopy (XPS, UPS), metastable impact electron spectroscopy (MIES), and small-angle neutron scattering (SANS). The peptization of the nanoparticles with suitable surfactants (oleic and lauric acid, sodium dioctylsulfosuccinate (AOT), LP-4 (a fatty acid condensation polymer), and KorantinSH (N-oleyl sarcosine)) yields magnetic fluids dispersed in carrier liquids such as toluene, kerosene, vacuum and mineral oils which are remarkably stable in air under ambient conditions. The resulting magnetic fluids show good magnetic properties. Several methods for the preparation of water-based MF are presented, e.g., formation of surfactant bilayers, using phase transfer agents, or surface modification with L-cysteine ethyl ester. Water-based metallic magnetic fluids have a high potential for a number of technical and biomedical applications. Technical applications of the Co-based ferrofluids in the field of positioning systems and magnetohydrostatic bearings were investigated. The results emphasize the scope of nanoparticulate ferrofluids having a metallic core.
Precipitated Iron Oxide Particles by Cyclic Growth
Authors: Müller Robert , Steinmetz H. , Zeisberger M. , Schmidt Ch. , Dutz S. , Hergt R. , Gawalek W.
Published: February 2006

Magnetic fluids show heating effects in ac-magnetic fields which may be useful for application in magnetic hyperthermia proposed as a tumour therapy. Enhancement of the specific loss power (SLP) of magnetic ac-losses would allow a reduction of the tissue load with magnetic material (iron oxide). The several types of loss processes depend strongly on the mean particle size [1] and the size distribution width [2]. To influence and improve the mean size as well as size distribution new approaches in preparation are promising where nucleation and growth of the particles can be influenced independently or where a further growing is possible on small given particles without further nucleation.

First experiments on iron oxide powders by a cyclic method based on “conventional” precipitation from Fe-salt solution have shown the feasibility of cyclic growth in an aqueous system. An increasing mean particle size (in the range from about 10 to 30 nm) with increasing number of cycles (up to four) is confirmed by XRD. Magnetic parameters of the saturation hysteresis loop and magnetic hysteresis losses calculated from minor loops are shown. The coercivity increases with the particle size, whereas the hysteresis losses at small applied fields (11 kA/m) reveal lower values again if the particles are magnetically too hard.
Thermal Ratchet Effect in a Rotating Ferrofluid
Authors: Becker Volker , Engel Andreas
Published: February 2006

Rotational Brownian motion of a colloidal magnetic particle in a ferrofluid under the influence of an external magnetic field may give rise to a noise induced rotation of the particle due to the rectification of thermal fluctuations. Via viscous coupling the associated angular momentum is transferred to the carrier liquid and can be measured as a macroscopic torque. In the present contribution we study the case of a rotating ferrofluid and elucidate the interplay between the ratchet effect and the non-zero vorticity of the flow.
Some Immobilization Modes of Biologically Active Substances to Fine Magnetic Particles
Authors: Závišová V. , Koneracká M. , Tomašovičová N. , Kopčanský P. , Timko M.
Published: February 2006

This paper describes the preparation, characterization and compare of three different modes for coupling biologically active substances to magnetic particles: (i) covalently bound proteins and enzymes to freshly prepared magnetite in the presence of carbodiimide (CDI), (ii) the encapsulation of magnetic nanoparticles and drugs in lipid mixture dipalmitoylphosphatidylcholine (DPPC) and (iii) the encapsulation of magnetic nanoparticles and drugs in biodegradable poly D,L-lactide polymer (PLA).
On Magnetic Field Control Experiments of Ferrofluid Convection Motion
Authors: Bozhko A.A. , Putin G.F. , Beresneva E.N. , Bulychev P.V.
Published: February 2006

The experiments have been performed on the stability of buoyancy-driven flows of a ferrofluid for the cases of an inclined and vertical orientation of thin cylindrical encloser. Visualization of flow patterns is provided by a temperature-sensitive liquid crystal sheet which serves as the lower surface of a transparent heat exchanger. The local temperature sensor is used for measurement of heat transport across the fluid layer. The results indicate that with the help of an external homogeneous transversal magnetic field it is possible to control the stability of thermogravitational shear flow under vertical orientation of the layer, i.e. induce the thermomagnetic mode of instability with vertical orientation of longitudinal convection rolls. As numerous experimental investigations show the origin of concentration density gradients due to gravity sedimentation of magnetic particles and their aggregates results in traveling wave regimes of Rayleigh and thermomagnetic convection flows.
Diagnostic value of various biochemical parameters for the diagnosis of pheochromocytoma in patients with adrenal mass
Authors: Unger Nicole , Pitt Christian , Schmidt Ingo Lopez , Walz Martin K , Schmid Kurt W , Philipp Thomas , Mann Klaus , Petersenn Stephan
Published: February 2006

Objective: Pheochromocytomas are neoplasms generally characterized by the autonomous production of catecholamines. This study compared various biochemical parameters for the diagnosis of adrenal pheochromocytoma in patients with adrenal mass.

Design: One hundred and fifty subjects were studied, including 24 histologically proven pheochromocytomas, 17 aldosterone-secreting and 21 cortisol-secreting adrenal adenomas and 30 nonfunctioning adrenal masses, 16 patients with essential hypertension and 42 healthy normotensive volunteers. Spontaneous blood samples and 24-h urine samples were collected prospectively.

Methods: Plasma and urinary epinephrine and norepinephrine levels were measured by high performance liquid chromatography, whereas plasma and urinary metanephrine and normetanephrine levels were determined by radioimmunoassay (RIA). Putative ratio thresholds were calculated by receiver operating characteristic (ROC) analysis to balance between sensitivity and specificity.

Results: Plasma normetanephrine was found to be the best single parameter with the highest sensitivity (91.7%) and specificity (95.6%) using a threshold of 126 pg/ml. In combination, plasma normetanephrine and metanephrine had a higher sensitivity of 95.8% with lower specificity (79.4%). All other combinations of plasma and/or urinary parameters demonstrated a lower accuracy.

Conclusion: Plasma metanephrines measured by RIA are reliable screening parameters for the diagnosis of pheochromocytoma.
Is systematic screening for thyroid disorders indicated in subfertile men?
Authors: Poppe K , Glinoer D , Tournaye H , Maniewski U , Haentjens P , Velkeniers B
Published: February 2006

Context: Data on the prevalence of thyroid disorders in male subfertility remain scarce.

Objective: To investigate the prevalence of thyroid dysfunction and thyroid autoimmunity in men with normal and abnormal semen characteristics.

Setting: Tertiary referral center for reproductive medicine of the University Hospital AZ-VUB, Brussels, Belgium.

Patients and design: Two hundred and ninety-two men were stratified according to the presence of normal (group 1;n= 39) or abnormal (group 2;n= 253) semen characteristics. Thyroid function was assessed by serum thyrotropin (TSH) and free thyroxine (FT4), and thyroid peroxidase antibodies (TPO-Ab) for thyroid autoimmunity (TAI or TPO-Ab > 34 kU/l); both were correlated with semen characteristics.

Main outcome measures: Semen characteristics were determined by World Health Organisation criteria (rapid + slow motility ≥ 50% and concentration ≥ 20 × 106) and Kruger criteria (morphology ≥ 14% normal cells).

Results: In group 1, the mean (±s.d.) age was 33 ± 4 years; serum TSH was 1.6 (0.3–29.6) mU/l (median (range)) and FT4 was 12.2 (8.8–15.6) ng/l. In group 2, the mean age was 33 ± 5 years, serum TSH was 1.3 (0.3–5.2) mU/l and FT4 was 12.5 (8.4–17.5) ng/l; (compared with group 1P= 0.008 for TSH andP= 0.037 for FT4). In both groups, one patient had increased TSH (2.6% and 0.4%;P= not significant (ns)). In group 1, one patient had TAI and in group 2 twelve patients had TAI (2.6% compared with 4.7%;P= ns). FT4 was an independent determinant for semen characteristics.

Conclusions: The prevalence of thyroid dysfunction and autoimmunity is comparable between men with normal and abnormal semen characteristics. On the basis of these data, we do not advise systematic screening for thyroid disorders in subfertile men consulting a tertiary referral center for reproductive medicine.
Effect of rosiglitazone on plasma adiponectin levels and arterial stiffness in subjects with prediabetes or non-diabetic metabolic syndrome
Authors: Kim Sin Gon , Ryu Ohk Hyun , Kim Hee Young , Lee Kye Won , Seo Ji A , Kim Nan Hee , Choi Kyung Mook , Lee Juneyoung , Baik Sei Hyun , Choi Dong Seop
Published: February 2006

Objective: Thiazolidinediones have favorable influences on surrogate markers of atherosclerosis such as adiponectin, and arterial stiffness in diabetic patients. However, it is not well known whether these beneficial effects occur in subjects without diabetes, such as prediabetes or the non-diabetic metabolic syndrome (MetS). The present study was therefore designed to evaluate the effectiveness of the insulin-sensitizing agent rosiglitazone on circulating adipocytokine levels and brachial-ankle pulse wave velocity (baPWV) in non-diabetics.

Design and methods: Ninety-nine subjects with prediabetes or non-diabetic MetS were randomly assigned to either rosiglitazone or an untreated control group (50 and 49 subjects respectively). The rosiglitazone group was treated daily for 12 weeks with 4 mg rosiglitazone. All subjects received a 75 g oral glucose test (OGTT) before and after treatment. In addition, baPWV, together with the levels of adiponectin, resistin, and high sensitivity C-reactive protein (hsCRP) were determined.

Results: Rosiglitazone treatment significantly increased circulating adiponectin levels (P < 0.001) relative to the control group (P = 0.21). Plasma resistin levels were unchanged in both the rosiglitazone-treated and -untreated groups, but baPWV and hsCRP were significantly decreased (P < 0.001 and P = 0.003 respectively) in the rosiglitazone group only. Multiple linear regression analysis showed that changes in plasma adiponectin and baPWV were significantly affected by rosiglitazone treatment.

Conclusions: These data suggest that rosiglitazone may have an anti-atherogenic effect in subjects with prediabetes or non-diabetic MetS.
Relationships between serum leptin and bone markers during stable weight, weight reduction and weight regain in male and female judoists
Authors: Prouteau S , Benhamou L , Courteix D
Published: February 2006

Objective: Despite a preliminary understanding of leptin–skeletal interactions, data in humans are inconsistent and the exact roles of leptin on bone metabolism have not yet been defined. The aim of this study was to examine the possible role of leptin in the regulation of bone metabolism in healthy, physically trained adults.

Methods and Design: Body composition and bone mass (dual-energy X-ray absorptiometry), anthropometry, serum leptin, insulin, cortisol, osteocalcin, C-terminal telopeptide of type I collagen (CTx) and total plasma proteins were measured in judoists at normal body weight, after weight reduction and after weight regain. Physical training, weight cycling history, menstrual status and nutritional intake using a 7-day food record were assessed.

Results: Precompetitive weight loss averaged 4 ± 0.3% of bodyweight and resulted in a significant decrease in leptin levels of 64% (P < 0.001) and of 31% for insulin (P < 0.0001). CTx and cortisol concentrations rose by 33% (P < 0.0001) and 81% (P < 0.05) respectively. Osteocalcin and total plasma protein remained unaffected by weight loss. A 4 ± 0.5% weight regain induced a 276% increase in leptin levels (P < 0.001) and an 18% increase in insulin (P < 0.001). CTx and cortisol decreased by 23% (P < 0.0001) and 27% (P < 0.05) respectively. Changes in leptin were significantly correlated with changes in bone resorption marker in response to both weight loss (r = 0.56, P < 0.01) and regain (r = 0.44, P < 0.05).

Conclusions: These findings suggest that leptin is involved in the regulation of bone metabolism in healthy adults and might play a potential role in the prevention of osteoporosis.
Low-density lipoprotein apolipoprotein B100 turnover in hypopituitary patients with GH deficiency: a stable isotope study
Authors: Christ Emanuel R , Cummings Michael H , Stolinski Michael , Jackson Nicola , Lumb Peter J , Wierzbicki Anthony S , Sönksen Peter H , Russell-Jones David L , Umpleby A Margot
Published: February 2006

Background: Epidemiological studies suggest that hypopituitary patients have an increased risk for cardiovascular mortality. The dyslipidaemia associated with this condition is often characterised by an increase in total cholesterol (TC) and low-density lipoprotein (LDL) cholesterol (LDL-C) and may contribute to these findings. The underlying mechanisms are not fully elucidated.

Materials and Methods: LDL apolipoprotein B (apoB) production rate and metabolic clearance rate were measured in seven patients with hypopituitarism (including GH deficiency) under stable conventional replacement therapy (three males and four females; age 40–16.1 years; body mass index 29.0–6.1 kg/m2(means ±s.d.)) and seven age-, gender- and body mass index-matched control subjects with an infusion of 1-13C-leucine. Fasting lipid profile and lipid composition of LDL were also measured.

Results: Fasting TC, triglycerides (TG), high-density lipoprotein-C, LDL-C and free fatty acid concentrations were not different between hypopituitary patients and control subjects. LDL-TG (P< 0.006) and LDL-TG/LDL apoB ratio (P< 0.02) were significantly increased in hypopituitary patients. LDL apoB pool size was not statistically different between patients and control subjects. In the hypopituitary patients, LDL apoB metabolic clearance rate (P< 0.05) and LDL apoB production rate (P< 0.02) were lower than in the control subjects.

Conclusions: The present results suggest that LDL apoB turnover and LDL composition is altered in hypopituitary patients. Whether these findings explain the increased risk for cardiovascular disease in hypopituitary patients remains to be established.
The effect of increased lipid intake on hormonal responses during aerobic exercise in endurance-trained men
Authors: Christ Emanuel R , Zehnder Monica , Boesch Chris , Trepp Roman , Mullis Primus E , Diem Peter , Décombaz Jacques
Published: February 2006

In view of the growing health problem associated with obesity, clarification of the regulation of energy homeostasis is important. Peripheral signals, such as ghrelin and leptin, have been shown to influence energy homeostasis. Nutrients and physical exercise, in turn, influence hormone levels. Data on the hormonal response to physical exercise (standardized negative energy balance) after high-fat (HF) or low-fat (LF) diet with identical carbohydrate intake are currently not available. The aim of the study was to investigate whether a short-term dietary intervention with HF and LF affects ghrelin and leptin levels and their modulators, GH, insulin and cortisol, before and during aerobic exercise. Eleven healthy, endurance-trained male athletes (Wmax 365 ± 29 W) were investigated twice in a randomized crossover design following two types of diet: 1. LF – 0.5 g fat/kg body weight (BW) per day for 2.5 days; 2. HF – 0.5 g fat/kg BW per day for 1 day followed by 3.5 g fat/kg BW per day for 1.5 days. After a standardized carbohydrate snack in the morning, metabolites and hormones (GH, ghrelin, leptin, insulin and cortisol) were measured before and at regular intervals throughout a 3-h aerobic exercise test on a cycloergometer at 50% of Wmax. Diet did not significantly affect GH and cortisol concentrations during exercise but resulted in a significant increase in ghrelin and decrease in leptin concentrations after LF compared with HF diet (area under the curve (AUC) ghrelin LF vs HF: P < 0.03; AUC leptin LF vs HF: P < 0.02, Wilcoxon rank test). These data suggest that acute negative energy balance induced by exercise elicits a hormonal response with opposite changes of ghrelin and leptin. In addition, the hormonal response is modulated by the preceding intake of fat.
Kinetics and secretion of placental growth hormone around parturition
Authors: Fuglsang Jens , Sandager Puk , Møller Niels , Fisker Sanne , Ørskov Hans , Ovesen Per
Published: February 2006

Objective: During pregnancy, placental growth hormone (PGH) is secreted into the maternal circulation, replacing pituitary GH. It is controversial whether PGH levels decline during vaginal birth. After placental expulsion, PGH is eliminated from the maternal blood. GH binding protein (GHBP) and body mass index (BMI) influence GH kinetics, but their impact on PGH kinetics is unknown. The present study was undertaken to define the kinetics of PGH during vaginal delivery and Caesarian section and to relate these kinetics to GHBP and BMI.

Design: A short term, prospective cohort study.

Methods: Twelve women had repeated blood samples drawn during vaginal delivery. From 26 women undergoing planned Caesarian delivery (CS) repeated blood samples were withdrawn before, during and after the CS, allowing PGH half-life determination.

Results: During vaginal delivery, median PGH values did not change before expulsion of the placenta, although individual fluctuations were seen. Clearance of PGH from the maternal circulation was best described by a two-compartment model. The initial half-life of serum PGH was (mean ± s.d.) 5.8 ± 2.4 min, and the late half-life was (median) 87.0 min (range: 25.1–679.6 min). The late half-life was correlated to the pre-gestational BMI (r = 0.39, P = 0.047), but not to the serum GHBP concentration.

Conclusions: Serum PGH did not decrease significantly during vaginal delivery. Elimination of PGH fitted a two-compartment model, with an estimated initial half-life of 5.8 min. The late phase serum half-life of PGH was related to BMI, suggesting a role for maternal fat mass in PGH metabolism.
Adrenal incidentaloma – follow-up results from a Swedish prospective study
Authors: Bülow Birgitta , Jansson Svante , Juhlin Claes , Steen Lars , Thorén Marja , Wahrenberg Hans , Valdemarsson Stig , Wängberg Bo , Ahréen Bo , _ _
Published: February 2006

Objectives: To examine the risk of developing adrenal carcinomas and clinically overt hypersecreting tumours during short-term follow-up in patients with adrenal incidentalomas.

Design: 229 (98 males and 131 females) patients with adrenal incidentalomas were investigated in a prospective follow-up study (median time 25 months; range 3–108 months). The patients were registered between January 1996 and July 2001 and followed until December 2004. Twenty-seven Swedish hospitals contributed with follow-up results.

Methods: Diagnostic procedures were undertaken according to a protocol including reinvestigation with computed tomography scans after 3–6 months, 15–18 months and 27–30 months, as well as hormonal evaluation at baseline and after 27–30 months of follow-up. Operation was recommended when the incidentaloma size increased or if there was a suspicion of a hypersecreting tumour.

Results: The median age at diagnosis of the 229 patients included in the follow-up study was 64 years (range 28–84 years) and the median size of the adrenal incidentalomas when discovered was 2.5 cm (range 1–8 cm). During the follow-up period, an increase in incidentaloma size of ≥0.5 cm was reported in 17 (7.4%) and of ≥1.0 cm was reported in 12 (5.2%) of the 229 patients. A decrease in size was seen in 12 patients (5.2%). A hypersecreting tumour was found in 2% of the hormonally investigated patients: Cushing’s syndrome (n = 2) and phaeochromocytoma (n = 1). Eleven patients underwent adrenalectomy, but no cases of primary adrenal malignancy were observed.

Conclusions: Patients with adrenal incidentaloma had a low risk of developing malignancy or hormonal hypersecretion during a short-term follow-up period.
Influence of two different GH dosage regimens on final height, bone geometry and bone strength in GH-deficient children
Authors: Radetti Giorgio , D’Addato Gianluca , Gatti Davide , Bozzola Mauro , Adami Silvano
Published: February 2006

Objective: The aim was to investigate the effects of two different GH dosage regimens on growth, bone geometry and bone strength.

Subjects and methods: Final height; parentally adjusted final height; the metacarpal index (MI) SDS, the inner and outer diameters; and the total cross-sectional area (CSA), cortical CSA, medullary CSA and bone strength (Bending Breaking Resistance Index (BBRI)) were evaluated at the metacarpal site in two cohorts of GH-deficient children, treated with two different doses of GH. Group 1 (38 patients) was treated with 0.16 mg/kg body weight per week of GH and group 2 (37 patients) with 0.3 mg/kg per week.

Results: At the end of treatment, with group 1 vs group 2, height SDS was −0.84 ± 1.07 vs −0.46 ± 0.76, and parentally adjusted height SDS was 0.14 ± 1.08 vs 0.27 ± 0.82. Parentally adjusted relative height gain was 1.14 ± 0.89 vs 2.14 ± 0.72 SDS (P < 0.0001). MI SDS was 0.58 ± 1.31 vs −0.42 ± 1.54 (P < 0.005). MI SDS gain was 0.07 ± 1.41 vs −0.35 ± 1.85. There was no difference between groups in the outer and inner diameter, in the total and cortical CSAs, whereas medullary CSA was higher in group 2 (P < 0.05). BBRI was 10.02 ± 5.37 vs 11.52 ± 5.49 cm3, and BBRI gain was 3.33 ± 5.06 vs 6.88 ± 6.65 (P = 0.01). P values were assessed using student’s t-test.

Conclusion: Higher GH doses result in a greater height gain and improved bone strength.