Statistics of lattice animals (polyominoes) and polygons

We have developed an improved algorithm that allows us to enumerate the number of site animals (polyominoes) on the square lattice up to size 46. Analysis of the resulting series yields an improved estimate, $\tau = 4.062570(8)$, for the growth constant of lattice animals and confirms to a very high degree of certainty that the generating function has a logarithmic divergence. We prove the bound $\tau > 3.90318.$ We also calculate the radius of gyration of both lattice animals and polygons enumerated by area. The analysis of the radius of gyration series yields the estimate $\nu = 0.64115(5)$, for both animals and polygons enumerated by area. The mean perimeter of polygons of area $n$ is also calculated. A number of new amplitude estimates are given.Comment: 10 pages, 2 eps figure

Linear response functions for a vibrational configuration interaction state

Linear response functions are implemented for a vibrational configuration interaction state allowing accurate analytical calculations of pure vibrational contributions to dynamical polarizabilities. Sample calculations are presented for the pure vibrational contributions to the polarizabilities of water and formaldehyde. We discuss the convergence of the results with respect to various details of the vibrational wave function description as well as the potential and property surfaces. We also analyze the frequency dependence of the linear response function and the effect of accounting phenomenologically for the finite lifetime of the excited vibrational states. Finally, we compare the analytical response approach to a sum-over-states approac

Biopsy-based optimization and calibration of a signal-intensity-ratio-based MRI method (1.5 Tesla) in a dextran-iron loaded mini-pig model, enabling estimation of very high liver iron concentrations

OBJECTIVE: Magnetic resonance imaging (MRI)-based techniques for non-invasive assessing liver iron concentration (LIC) in patients with iron overload have a limited upper measuring range around 35 mg/g dry weight, caused by signal loss from accelerated T1-, T2-, T2* shortening with increasing LIC. Expansion of this range is necessary to allow evaluation of patients with very high LIC. AIM: To assess measuring range of a gradient-echo R2* method and a T1-weighted spin-echo (SE), signal intensity ratio (SIR)-based method (TE = 25 ms, TR = 560 ms), and to extend the upper measuring range of the SIR method by optimizing echo time (TE) and repetition time (TR) in iron-loaded minipigs. METHODS: Thirteen mini pigs were followed up during dextran-iron loading with repeated percutaneous liver biopsies for chemical LIC measurement and MRIs for parallel non-invasive estimation of LIC (81 examinations) using different TEs and TRs. RESULTS: SIR and R2* method had similar upper measuring range around 34 mg/g and similar method agreement. Using TE = 12 ms and TR = 1200 ms extended the upper measuring range to 115 mg/g and yielded good method of agreement. DISCUSSION: The wider measuring range is likely caused by lesser sensitivity of the SE sequence to iron, due to shorter TE, leading to later signal loss at high LIC, allowing evaluation of most severe hepatic iron overload. Validation in iron-loaded patients is necessary

Hot electron driven enhancement of spin-lattice coupling in 4f ferromagnets observed by femtosecond x-ray magnetic circular dichroism

Femtosecond x-ray magnetic circular dichroism was used to study the time-dependent magnetic moment of 4 fs electrons in the ferromagnets Gd and Tb, which are known for their different spin-lattice coupling. We observe a two-step demagnetization with an ultrafast demagnetization time of 750 fs identical for both systems and slower times which differ sizeably with 40 ps for Gd and 8 ps for Tb. We conclude that spin-lattice coupling in the electronically excited state is enhanced up to orders of magnitude compared to equilibrium.Comment: added reference 24, clarified the meaning of photo-induced, emphasized that XMCD probes the magnetic moment localized at 4f electron

Use and impact of point-of-care ultrasonography in general practice:a prospective observational study

Objectives To describe how general practitioners (GPs) use point-of-care ultrasonography (POCUS) and how it influences the diagnostic process and treatment of patients.Design Prospective observational study using an online questionnaire before and after POCUS.Setting Office-based general practice.Participants Twenty GPs consecutively recruited all patients examined with POCUS in 1 month.Primary and secondary outcome measures We estimated the use of POCUS through the indication for use, the frequency of use, the time consumption, the extent of modification of the examination and the findings.The influence on the diagnostic process was estimated through change in the tentative diagnoses, change in confidence, the ability to produce ultrasound images and the relationship between confidence and organs scanned or tentative diagnoses.The influence of POCUS on patient treatment was estimated through change in plan for the patient, change in patient’s treatment and the relationship between such changes and certain findings.Results The GPs included 574 patients in the study. POCUS was used in patient consultations with a median frequency of 8.6% (IQR: 4.9–12.6). Many different organs were scanned covering more than 100 different tentative diagnoses. The median time taken to perform POCUS was 5 min (IQR: 3–8). Across applications and GPs, POCUS entailed a change in diagnoses in 49.4% of patients; increased confidence in a diagnosis in 89.2% of patients; a change in the management plan for 50.9% of patients including an absolute reduction in intended referrals to secondary care from 49.2% to 25.6%; and a change in treatment for 26.5% of patients.Conclusions The clinical utilisation of POCUS was highly variable among the GPs included in this study in terms of the indication for performing POCUS, examined scanning modalities and frequency of use. Overall, using POCUS altered the GPs’ diagnostic process and clinical decision-making in nearly three out of four consultations.Trial registration number NCT03375333

Improving a real-time object detector with compact temporal information

Neural networks designed for real-time object detectionhave recently improved significantly, but in practice, look-ing at only a single RGB image at the time may not be ideal.For example, when detecting objects in videos, a foregrounddetection algorithm can be used to obtain compact temporaldata, which can be fed into a neural network alongside RGBimages. We propose an approach for doing this, based onan existing object detector, that re-uses pretrained weightsfor the processing of RGB images. The neural network wastested on the VIRAT dataset with annotations for object de-tection, a problem this approach is well suited for. The ac-curacy was found to improve significantly (up to 66%), witha roughly 40% increase in computational time

Dynamical Ordering of Driven Stripe Phases in Quenched Disorder

We examine the dynamics and stripe formation in a system with competing short and long range interactions in the presence of both an applied dc drive and quenched disorder. Without disorder, the system forms stripes organized in a labyrinth state. We find that, when the disorder strength exceeds a critical value, an applied dc drive can induce a dynamical stripe ordering transition to a state that is more ordered than the originating undriven, unpinned pattern. We show that signatures in the structure factor and transport properties correspond to this dynamical reordering transition, and we present the dynamic phase diagram as a function of strengths of disorder and dc drive.Comment: 4 pages, 4 postscript figure

Altered PI3-kinase/Akt signalling in skeletal muscle of young men with low birth weight.

BACKGROUND: Low birth weight (LBW) is associated with increased future risk of insulin resistance and type 2 diabetes mellitus. The underlying molecular mechanisms remain poorly understood. We have previously shown that young LBW men have reduced skeletal muscle expression of PI3K p85alpha regulatory subunit and p110beta catalytic subunit, PKCzeta and GLUT4 in the fasting state. The aim of this study was to determine whether insulin activation of the PI3K/Akt and MAPK signalling pathways is altered in skeletal muscle of young adult men with LBW. METHODS: Vastus lateralis muscle biopsies were obtained from 20 healthy 19-yr old men with BW< or = 10th percentile for gestational age (LBW) and 20 normal birth weight controls (NBW), matched for physical fitness and whole-body glucose disposal, prior to (fasting state) and following a 4-hr hyperinsulinemic euglycemic clamp (insulin stimulated state). Expression and phosphorylation of selected proteins was determined by Western blotting. PRINCIPAL FINDINGS: Insulin stimulated expression of aPKCzeta (p<0.001) and Akt1 (p<0.001) was decreased in muscle of LBW men when compared to insulin stimulated controls. LBW was associated with increased insulin stimulated levels of IRS1 (p<0.05), PI3K p85alpha (p<0.001) and p110beta (p<0.05) subunits, while there was no significant change in these proteins in insulin stimulated control muscle. In addition LBW had reduced insulin stimulated phospho-Akt (Ser 473) (p<0.01), indicative of reduced Akt signalling. Insulin stimulated expression/phosphorylation of all the MAPK proteins studied [p38 MAPK, phospho-p38 MAPK (Thr180/Tyr182), phospho-ERK (Thr 202/Tyr204), JNK1, JNK2 and phospho-JNK (Thr 183/Tyr185)] was not different between groups. CONCLUSIONS: We conclude that altered insulin activation of the PI3K/Akt but not the MAPK pathway precedes and may contribute to development of whole-body insulin resistance and type 2 diabetes in men with LBW

Genetic variation in the serotonin transporter gene (5-HTTLPR, rs25531) influences the analgesic response to the short acting opioid Remifentanil in humans

<p>Abstract</p> <p>Background</p> <p>There is evidence from animal studies that serotonin (5-HT) can influence the antinociceptive effects of opioids at the spinal cord level. Therefore, there could be an influence of genetic polymorphisms in the serotonin system on individual variability in response to opioid treatment of pain. The serotonin transporter (5-HTT) is a key regulator of serotonin metabolism and availability and its gene harbors several known polymorphisms that are known to affect 5-HTT expression (e.g. 5-HTTLPR, rs25531). The aim of this study was to investigate if the triallelic 5-HTTLPR influences pain sensitivity or the analgesic effect of opioids in humans. 43 healthy volunteers (12 men, 31 women, mean age 26 years) underwent heat pain stimulations before and after intravenous injection of Remifentanil; a rapid and potent opioid drug acting on μ-type receptors. Subjects rated their perceived pain on a visual analogue scale (VAS). All participants were genotyped for the 5-HTTLPR and the rs25531 polymorphism. We recruited by advertising, with no history of drug abuse, chronic pain or psychiatric disorders.</p> <p>Results</p> <p>At baseline, there was no difference in pain ratings for the different triallelic 5-HTTLPR genotype groups. However, the opiod drug had a differential analgesic effect depending on the triallelic 5-HTTLPR genotype. Remifentanil had a significantly better analgesic effect in individuals with a genotype coding for low 5-HTT expression (S_A/S_Aand S_A/L_G) as compared to those with high expression(L_A/L_A), p < 0.02. The analgesic effect for the three different genotype groups was linear to degree of 5-HTT expression.</p> <p>Conclusion</p> <p>This is the first report showing an influence of the triallelic 5-HTTLPR on pain sensitivity or the analgesic effect of opioids in humans. Previously the 5-HTTLPR s-allele has been associated with higher risk of developing chronic pain conditions but in this study we show that the genotype coding for low 5-HTT expression is associated with a better analgesic effect of an opioid. The s-allele has been associated with downregulation of 5-HT1 receptors and we suggest that individuals with a desensitization of 5-HT1 receptors have an increased analgesic response to opioids during acute pain stimuli, but may still be at increased risk of developing chronic pain conditions.</p