On the use of spatially discrete data to compute energy and mass balance

In many practical applications the state of field soils is monitored by recording the evolution of temperature and soil moisture at discrete depths. We theoretically investigate the systematic errors that arise when mass and energy balances are computed directly from these measurements. We show that, even with no measurement or model errors, large residuals might result when finite difference approximations are used to compute fluxes and storage term. To calculate the limits set by the use of spatially discrete measurements on the accuracy of balance closure, we derive an analytical solution to estimate the residual on the basis of the two key parameters: the penetration depth and the distance between the measurements. When the thickness of the control layer for which the balance is computed is comparable to the penetration depth of the forcing (which depends on the thermal diffusivity and on the forcing period) large residuals arise. The residual is also very sensitive to the distance between the measurements, which requires accurately controlling the position of the sensors in field experiments. We also demonstrate that, for the same experimental setup, mass residuals are sensitively larger than the energy residuals due to the nonlinearity of the moisture transport equation. Our analysis suggests that a careful assessment of the systematic mass error introduced by the use of spatially discrete data is required before using fluxes and residuals computed directly from field measurements.

Premature epiphyseal closure in an adolescent treated by retinoids for acne: an unusual cause of anterior knee pain.

Retinoids are effective and widely prescribed in the treatment of severe acne. However their use can be associated with numerous side effects. Some rare cases of premature epiphyseal closure were reported. We present the case of a sixteen-year-old soccer player referred for progressive anterior pain in both knees, evoking a patellar problem. Careful pharmacological questioning revealed use of isotretinoin for several months. MRI findings showed an irregularity of the growth plate and an important metaphyso-epiphyseal oedema, more noticeable in the left knee. Retinoid-induced premature epiphyseal closure was diagnosed. The treatment was stopped, with a resolution of pain within two months. After recovery a persisting small sequelar thumbprint-like growth plate lesion was observed on the control MRI. Retinoids induce an invasion of the growth plate by osteoclasts and a decrease in proteoglycans synthesis. It seems that the knee is the most affected joint. This complication being rare, a radiological follow-up of the young patients treated by retinoids is not proposed.

Dietary fat, lipogenesis and energy balance.

Today, there are still uncertainties about the role of exogenous fat on body fat regulation. Early models of energy utilization (for example, Kleiber's, early 20th century) failed to take into account the nature of substrate oxidized in the control of food intake, whereas more recent models (e.g., Flatt's model, end of 20th century) did. Excess body fat storage is ultimately a problem of chronic positive energy balance mediated by a poor control of energy intake or/and a blunted total energy expenditure. Excess fat storage can stem from exogenous fat and to a more limited extent by nonfat substrates precursors transformed into body fat, mostly from carbohydrates, a process known as de novo lipogenesis. When considered over periods of weeks, months or years, total fat balance is closely related to energy balance. Over periods of days, the net change in fat balance is quantitatively limited as compared to the size of endogenous fat storage. The issues discussed in this article primarily include the stimulation of de novo lipogenesis after acute or prolonged CHO overfeeding and whether de novo lipogenesis is a risk factor for obesity development.

Loss of Cutaneous TSLP-Dependent Immune Responses Skews the Balance of Inflammation from Tumor Protective to Tumor Promoting.

Inflammation can promote or inhibit cancer progression. In this study we have addressed the role of the proinflammatory cytokine thymic stromal lymphopoietin (TSLP) during skin carcinogenesis. Using conditional loss- and gain-of-function mouse models for Notch and Wnt signaling, respectively, we demonstrate that TSLP-mediated inflammation protects against cutaneous carcinogenesis by acting directly on CD4 and CD8 T cells. Genetic ablation of TSLP receptor (TSLPR) perturbs T-cell-mediated protection and results in the accumulation of CD11b(+)Gr1(+) myeloid cells. These promote tumor growth by secreting Wnt ligands and augmenting β-catenin signaling in the neighboring epithelium. Epithelial specific ablation of β-catenin prevents both carcinogenesis and the accumulation of CD11b(+)Gr1(+) myeloid cells, suggesting tumor cells initiate a feed-forward loop that induces protumorigenic inflammation.

PFO closure vs. medical therapy in cryptogenic stroke or transient ischemic attack: A systematic review and meta-analysis.

BACKGROUND/OBJECTIVES: This study aims to assess whether patent foramen ovale (PFO) closure is superior to medical therapy in preventing recurrence of cryptogenic ischemic stroke or transient ischemic attack (TIA). METHODS: We searched PubMed for randomized trials which compared PFO closure with medical therapy in cryptogenic stroke/TIA using the items: "stroke or cerebrovascular accident or TIA" and "patent foramen ovale or paradoxical embolism" and "trial or study". RESULTS: Among 650 potentially eligible articles, 3 were included including 2303 patients. There was no statistically significant difference between PFO-closure and medical therapy in ischemic stroke recurrence (1.91% vs. 2.94% respectively, OR: 0.64, 95%CI: 0.37-1.10), TIA (2.08% vs. 2.42% respectively, OR: 0.87, 95%CI: 0.50-1.51) and death (0.60% vs. 0.86% respectively, OR: 0.71, 95%CI: 0.28-1.82). In subgroup analysis, there was significant reduction of ischemic strokes in the AMPLATZER PFO Occluder arm vs. medical therapy (1.4% vs. 3.04% respectively, OR: 0.46, 95%CI: 0.21-0.98, relative-risk-reduction: 53.2%, absolute-risk-reduction: 1.6%, number-needed-to-treat: 61.8) but not in the STARFlex device (2.7% vs. 2.8% with medical therapy, OR: 0.93, 95%CI: 0.45-2.11). Compared to medical therapy, the number of patients with new-onset atrial fibrillation (AF) was similar in the AMPLATZER PFO Occluder arm (0.72% vs. 1.28% respectively, OR: 1.81, 95%CI: 0.60-5.42) but higher in the STARFlex device (0.64% vs. 5.14% respectively, OR: 8.30, 95%CI: 2.47-27.84). CONCLUSIONS: This meta-analysis does not support PFO closure for secondary prevention with unselected devices in cryptogenic stroke/TIA. In subgroup analysis, selected closure devices may be superior to medical therapy without increasing the risk of new-onset AF, however. This observation should be confirmed in further trials using inclusion criteria for patients with high likelihood of PFO-related stroke recurrence.

Macronutrients and energy balance in obesity.

Energy balance is the difference between metabolizable energy intake and total energy expenditure. Energy intake is difficult to measure accurately; changes in body weight, for example, are not a good measure of the adequacy of energy intake, because fluctuations in body weight are common even if the overall trend is toward weight loss. It is now customary to assess energy requirements indirectly from total energy expenditure. Total energy expenditure consists of basal metabolism, postprandial thermogenesis, and physical activity. Energy expenditure is related to both body weight and body composition. A reduction in total energy expenditure accompanies weight loss, because basal metabolic rate decreases with the loss of lean tissue mass. Similarly, with weight gain, there is an increase in basal metabolic rate, because lean tissue mass grows to support the increase in fat tissue mass. Excess energy intake over energy expenditure causes weight gain and an accompanying increase in total energy expenditure. Following a period of adaptation, total energy expenditure will match energy intake and body weight will stabilize at a higher level. This same relationship holds for weight loss. Respiratory quotient (measured in steady state) is an indication of the proportion of energy expenditure derived from fat and carbohydrate oxidation. Over long periods of time, fat balance is equivalent to energy balance, as an excess of fat intake over fat oxidation causes fat storage.

Wound infection after excision and primary midline closure for pilonidal disease: risk factor analysis to improve patient selection.

BACKGROUND: Excision and primary midline closure for pilonidal disease (PD) is a simple procedure; however, it is frequently complicated by infection and prolonged healing. The aim of this study was to analyze risk factors for surgical site infection (SSI) in this context. METHODS: All consecutive patients undergoing excision and primary closure for PD from January 2002 through October 2008 were retrospectively assessed. The end points were SSI, as defined by the Center for Disease Control, and time to healing. Univariable and multivariable risk factor analyses were performed. RESULTS: One hundred thirty-one patients were included [97 men (74%), median age = 24 (range 15-66) years]. SSI occurred in 41 (31%) patients. Median time to healing was 20 days (range 12-76) in patients without SSI and 62 days (range 20-176) in patients with SSI (P < 0.0001). In univariable and multivariable analyses, smoking [OR = 2.6 (95% CI 1.02, 6.8), P = 0.046] and lack of antibiotic prophylaxis [OR = 5.6 (95% CI 2.5, 14.3), P = 0.001] were significant predictors for SSI. Adjusted for SSI, age over 25 was a significant predictor of prolonged healing. CONCLUSION: This study suggests that the rate of SSI after excision and primary closure of PD is higher in smokers and could be reduced by antibiotic prophylaxis. SSI significantly prolongs healing time, particularly in patients over 25 years.

Prise en charge de l'ulcère de jambe d'origine veineuse [Management of venous leg ulcers].

Leg ulcers are a major health and economic problem especially in elderly. More than 70% are associated with venous disease. Compressive therapy is the most effective treatment but bandages are often poorly tolerated and well trained nurses are required to apply them effectively. In recent years, the VAC system (vacuum assisted closure) has profoundly changed the wound healing approach. The objective is now to regenerate the tissues and not to replace them with skin grafts which give uncertain results. The other important challenge is to prevent recurrences. New pharmacologic treatments acting on microcirculation and hemostasis would probably appear in the near future opening new therapeutic perspectives.

A 10-year experience in paediatric spontaneous cerebral hemorrhage: which children with headache need more than a clinical examination?

INTRODUCTION: When a child is seen in a clinic with a headache, stroke is certainly not the first on the list of differential diagnoses. In western countries, stroke is typically associated with adults and the elderly. Although rare, haemorrhagic strokes are not exceptional in the paediatric population, as their incidence is around 1/100 000/year. Prompt diagnosis is essential, since delayed treatment may lead to disastrous prognosis in these children. MATERIALS AND METHODS: This is a retrospective review of paediatric cases with spontaneous cerebral haemorrhage that presented in two university hospitals in the last ten years. The experience of these primary and tertiary referral centres comprises 22 consecutive cases that are analysed according to aetiology, presenting symptoms, treatment and outcome. RESULTS: 77% of the children diagnosed with haemorrhagic stroke presented with headaches. 41% of them had a sudden onset, while 9% developed headaches over a period of hours to weeks. While 9% presented only with headaches, the majority had either subtle (diplopia, balance problems) or obvious (focal deficits, unilateral weakness and decreased level of consciousness) concomitant neurological signs. 55% had an arteriovenous malformation (AVM), 18% had an aneurysm and 14% had a cavernous malformation. In 14% the aetiology could not be determined. The majority of haemorrhages (82%) were supratentorial, while 18% bled into the posterior fossa. All children underwent an emergency cerebral CT scan followed by specific investigations. The treatment was dependent on the aetiology as well as the mass effect of the haematoma. In 23% an emergent evacuation of the haematoma was performed. Two children (9%) died, and 75% had a favourable clinical outcome. CONCLUSION: Headaches in children are a common problem, and a small minority may reveal an intracranial haemorrhage with poor prognosis if not treated promptly. Although characterisation of headaches is more difficult in a paediatric population, sudden, unusual or intense headaches should lead to imaging work-up. Any neurological finding, even one as subtle as hemianopsia or dysmetria, should alarm the physician and should be followed by emergency imaging investigation. If the cerebral CT reveals a haemorrhage, the child should be referred immediately to a neurosurgical referral centre without further investigation. The outcome is grim for children presenting in coma with fixed, dilated pupils. The long-term result overall for children after spontaneous intracranial haemorrhage is not dismal and depends critically on specialised management.

Analysis of a finite volume element method for the Stokes problem

In this paper we propose a stabilized conforming finite volume element method for the Stokes equations. On stating the convergence of the method, optimal a priori error estimates in different norms are obtained by establishing the adequate connection between the finite volume and stabilized finite element formulations. A superconvergence result is also derived by using a postprocessing projection method. In particular, the stabilization of the continuous lowest equal order pair finite volume element discretization is achieved by enriching the velocity space with local functions that do not necessarily vanish on the element boundaries. Finally, some numerical experiments that confirm the predicted behavior of the method are provided.

Influence of the primary cleft palate closure on the future need for orthognathic surgery in unilateral cleft lip and palate patients.

The aim of the study was to determine the influence of the dissection of the palate during primary surgery and the type of orthognathic surgery needed in cases of unilateral total cleft. The review concerns 58 children born with a complete unilateral cleft lip and palate and treated between 1994 and 2008 at the appropriate age for orthognathic surgery. This is a retrospective mixed-longitudinal study. Patients with syndromes or associated anomalies were excluded. All children were treated by the same orthodontist and by the same surgical team. Children are divided into 2 groups: the first group includes children who had conventional primary cleft palate repair during their first year of life, with extensive mucoperiosteal undermining. The second group includes children operated on according to the Malek surgical protocol. The soft palate is closed at the age of 3 months, and the hard palate at 6 months with minimal mucoperiosteal undermining. Lateral cephalograms at ages 9 and 16 years and surgical records were compared. The need for orthognathic surgery was more frequent in the first than in the second group (60% vs 47.8%). Concerning the type of orthognathic surgery performed, 2- or 3-piece Le Fort I or bimaxillary osteotomies were also less required in the first group. Palate surgery following the Malek procedure results in an improved and simplified craniofacial outcome. With a minimal undermining of palatal mucosa, we managed to reduce the amount of patients who required an orthognathic procedure. When this procedure was indicated, the surgical intervention was also greatly simplified.

Les bases moléculaires de l'obésité : vers de nouvelles thérapeutiques ?

Obesity is an increasingly serious health problem, and is highly associated with insulin-resistance and dyslipidemia. The mechanisms involved in the development of this disorder are still poorly understood, although significant progress has been recently made in the elucidation of their molecular basis. The major causes leading to obesity are defects in the regulation of fat metabolism. Several mutations identified in different animal models have unveiled the roles of a number of genes in the regulation of energy balance. These dicoveries, together with the fact that some of these mutations have been found in humans, have lead to the conclusion that obesity is due to nutritional or environmental factors, but also involves genetic factors. A number of important peripheric factors participate in the regulation processes, such as the adipocyte-specific hormone leptin, and the nuclear homone receptors PPARs. A general scheme can now be drawn which includes some key factors and their respective interactions.

Subaortic ventricular septal defect closure: is the principle of harmony for a longer function no longer valid?

Comment on : Results of two different approaches to closure of subaortic ventricular septal defects in children. [Eur J Cardiothorac Surg. 2014]