Entropy maximization in the force network ensemble for granular solids

A long-standing issue in the area of granular media is the tail of the force distribution, in particular whether this is exponential, Gaussian, or even some other form. Here we resolve the issue for the case of the force network ensemble in two dimensions. We demonstrate that conservation of the total area of a reciprocal tiling, a direct consequence of local force balance, is crucial for predicting the local stress distribution. Maximizing entropy while conserving the tiling area and total pressure leads to a distribution of local pressures with a generically Gaussian tail that is in excellent agreement with numerics, both with and without friction and for two different contact networks.Comment: 4 pages, 3 figure

Co-morbidity and patterns of care in stimulant-treated children with ADHD in the Netherlands

This study aimed at investigating the use of psychosocial interventions and psychotropic co-medication among stimulant-treated children with attention-deficit hyperactivity disorder (ADHD) in relation to the presence of psychiatric co-morbidity. Stimulant users younger than 16 years were identified in 115 pharmacies and a questionnaire was sent to their stimulant prescribing physician. Of 773 questionnaires sent out, 556 were returned and were suitable for analysis (72%). The results are based on 510 questionnaires concerning stimulant-treated children for whom a diagnosis of ADHD was reported. Of the 510 children diagnosed with ADHD, 31% had also received one or more other psychiatric diagnoses, mainly pervasive developmental disorder or oppositional defiant disorder/conduct disorder. We found an association between the presence of co-morbidity and the use of psychosocial interventions for the child (P < 0.001) and the parents (P < 0.001). In the ADHD-only group, 26% did not receive any form of additional interventions, while psychosocial interventions varied from 8 to 18% in children with ADHD and psychiatric co-morbidity. The presence of diagnostic co-morbidity was also associated with the use of psychotropic co-medication (overall, P = 0.012) and antipsychotics (P < 0.001). Stimulant-treated youths with ADHD and psychiatric co-morbidity received more psychosocial interventions and psychotropic co-medication than children with ADHD-only. The type of psychosocial interventions and psychotropic co-medication received by the children and their parents, depended on the specific co-morbid psychiatric disorder being present

Genetic parameters of cryptorchidism and testis size in Friesian colts

In males with cryptorchidism, one or both testes do not descend into the scrotum thereby affecting among other things fertility. Testis size has been suggested to contribute to cryptorchidism. Therefore, the aim of our study was to estimate genetic parameters of cryptorchidism and testis size in Friesian colts. Data on cryptorchidism (0/1, n=1327) and testis size (cm, n=868 with size of both testes estimated) in Friesian colts of 1–7 months-of-age were gathered by a veterinarian during inspections from 2009 to 2012. Heritabilities, phenotypic and genetic correlations were estimated using ASReml4 including age of the colt (in months), location, year and month of inspection as fixed effects. Prevalence of cryptorchidism was 14.2%. Most affected colts (88.3%) were unilateral, while 11.7% were bilateral cases. Of the unilateral cases, significantly fewer colts had a left retained testis (35.5%) compared to a right retained testis (64.5%). Heritability of cryptorchidism was 0.13 (SE=0.06) and increased slightly when only cases of 4 months and older were considered. Based on literature and our findings we advise not to inspect colts at a very young age. Mean testis size significantly differed between left (3.47 cm) and right testis (3.19 cm). Heritability of left testis size (0.12±0.07) was lower compared to heritability of right testis size (0.31±0.10), where genetic correlation between left and right testis size was 0.87 (SE=0.12). The genetic correlation between left testis size and cryptorchidism was −0.94 (SE=0.15) and between right testis size and cryptorchidism was −0.64 (SE=0.23). At the age of the investigated Friesian colts, cryptorchidism genetically coincides with smaller testis size. The development of the left and right testis might differ, which could be hereditary in nature. More precise phenotyping, like recording position and size (and side) of the retained testis and age of the stallion, might contribute additionally to disentangling the genetic background of equine cryptorchidism and identifying the gene(s) affecting this disorder. For now, the continuation of the data recording as described in our study will enable the studbook to estimate breeding values and thereby select against cryptorchidism.</p

Parents report on stimulant-treated children in the Netherlands:Initiation of treatment and follow-up care

Objectives: The aim of this study was to describe current practices around initiation and follow-up care of stimulant treatment among stimulant-treated children in a nationwide survey among parents. Methods: A total of 115 pharmacies detected current stimulant users <16 years old in their pharmacy information system and sent parents a questionnaire regarding their child's stimulant treatment. Results: Parents returned 924 of 1,307 questionnaires (71%). The median age of the stimulant users was 10 years and 85% were boys. In all, 91% were diagnosed with attention-deficit/hyperactivity disorder (ADHD). In 77% of the cases, the child or parents received other therapies besides stimulants-21% received psychotropic co-medication, with melatonin (11%) and antipsychotics (7%) being mentioned most frequently. Stimulant use was primarily initiated by child psychiatrists (51%) and pediatricians (32%), but most children received repeat prescriptions from general practitioners (61%). Of these 924 children, 19% did not receive any follow-up care, and transfer of prescribing responsibility increased the risk of not receiving follow-up care. The 732 children (79%) who were monitored visited a physician approximately twice a year. During follow-up visits, pediatricians performed physical check ups significantly more often. Conclusion: Stimulant treatment in The Netherlands is initiated mainly by specialists such as child psychiatrists and pediatricians. In the current study, follow-up care for stimulant-treated children in The Netherlands appeared to be poor, suggesting an urgent need for improvement

Long-acting methylphenidate-OROS in youths with attention-deficit hyperactivity disorder suboptimally controlled with immediate-release methylphenidate:a study of cost effectiveness in The Netherlands

Background: Attention-deficit hyperactivity disorder (ADHD) is the most common mental health disorder in youths. Stimulants are the drugs of first choice in the treatment of ADHD. It has been suggested that full costs associated with the treatment of ADHD may be reduced by once-daily administration regimens of stimulants. Objectives: To estimate the cost effectiveness of treatment with long-acting methylphenidate osmotic release oral system (OROS) [Concerta (R)] for youths with ADHD for whom treatment with immediate-release (IR) methylphenidate is suboptimal. Study design: We developed a Markov model to obtain an incremental cost-effectiveness ratio (ICER). The analysis covered 10 years, with a Markov cycle of I day. Costs (in 2005 euros [sic) included medication, consultations and treatment interventions, and additional costs for attending special education. Quality-adjusted life-years (QALYs) were used as the effectiveness measure. Outcome probabilities were taken from the medical literature and an expert panel of five child psychiatrists and paediatricians. Univariate sensitivity analyses were performed to assess the robustness of the base-case estimate. Multivariate sensitivity analysis was used to estimate a worst- and best-case ICER. Results: The ICER of methylphenidate-OROS treatment in youths with ADHD for whom treatment with IR methylphenidate is suboptimal was (sic)2004 per QALY. Total costs after 10 years were (sic)15 739 for the IR methylphenidate pathway and (sic)16 015 for the methylphenidate-OROS pathway. In the univariate sensitivity analysis, the ICER was sensitive to changes in resource use and the probability of stopping stimulant treatment in favour of IR methylphenidate. An ICER of 0 was reached with a 6.2% price reduction of methylphenidate-OROS. Conclusion: Methylphenidate-OROS is a cost-effective treatment for youths with ADHD for whom treatment with IR methylphenidate is suboptimal. Higher medication costs of methylphenidate-OROS were compensated for by savings on resource use, yielding similar 10-year costs compared with treatment with IR methylphenidate. Our analysis is sensitive to both clinical parameters and (differences in) resource utilization and costs between the groups modelled, warranting further research within clinical trials and observational databases, and into the full scope of costs