Nonlinear Hydrodynamics of a Hard Sphere Fluid Near the Glass Transition

We conduct a numerical study of the dynamic behavior of a dense hard sphere fluid by deriving and integrating a set of Langevin equations. The statics of the system is described by a free energy functional of the Ramakrishnan-Yussouff form. We find that the system exhibits glassy behavior as evidenced through stretched exponential decay and two-stage relaxation of the density correlation function. The characteristic times grow with increasing density according to the Vogel-Fulcher law. The wavenumber dependence of the kinetics is extensively explored. The connection of our results with experiment, mode coupling theory, and molecular dynamics results is discussed.Comment: 34 Pages, Plain TeX, 12 PostScript Figures (not included, available on request

Ultrasonography of quadriceps femoris muscle and subcutaneous fat tissue and body composition by BIVA in chronic dialysis patients

Protein Energy Wasting (PEW) in hemodialysis (HD) patients is a multifactorial condition due to specific pathology-related pathogenetic mechanisms, leading to loss of skeletal muscle mass in HD patients. Computed Tomography and Magnetic Resonance Imaging still represent the gold standard techniques for body composition assessment. However, their widespread application in clinical practice is difficult and body composition evaluation in HD patients is mainly based on conventional anthropometric nutritional indexes and bioelectrical impedance vector analysis (BIVA). Little data is currently available on ultrasound (US)-based measurements of muscle mass and fat tissue in this clinical setting. The purpose of our study is to ascertain: (1) if there are differences between quadriceps rectus femoris muscle (QRFM) thickness and abdominal/thigh subcutaneous fat tissue (SFT) measured by US between HD patients and healthy subjects; (2) if there is any correlation between QRFM and abdominal/thigh SFT thickness by US, and BIVA/conventional nutritional indexes in HD patients. We enrolled 65 consecutive HD patients and 33 healthy subjects. Demographic and laboratory were collected. The malnutrition inflammation score (MIS) was calculated. Using B-mode US system, the QRFM and SFT thicknesses were measured at the level of three landmarks in both thighs (superior anterior iliac spine, upper pole of the patella, the midpoint of the tract included between the previous points). SFT was also measured at the level of the periumbilical point. The mono frequency (50 KHz) BIVA was conducted using bioelectrical measurements (Rz, resistance; Xc, reactance; adjusted for height, Rz/H and Xc/H; PA, phase angle). 58.5% were men and the mean age was 69 (SD 13.7) years. QRFM and thigh SFT thicknesses were reduced in HD patients as compared to healthy subjects (p < 0.01). Similarly, also BIVA parameters, expression of lean body mass, were lower (p < 0.001), except for Rz and Rz/H in HD patients. The average QRFM thickness of both thighs at top, mid, lower landmarks were positively correlated with PA and body cell mass (BCM) by BIVA, while negatively correlated with Rz/H (p < 0.05). Abdominal SFT was positively correlated with PA, BCM and basal metabolic rate (BMR) (p < 0.05). Our study shows that ultrasound QRFM and thigh SFT thicknesses were reduced in HD patients and that muscle ultrasound measurements were significantly correlated with BIVA parameters

Unsupervised Spike Sorting for Large-Scale, High-Density Multielectrode Arrays

We present a method for automated spike sorting for recordings with high-density, large-scale multielectrode arrays. Exploiting the dense sampling of single neurons by multiple electrodes, an efficient, low-dimensional representation of detected spikes consisting of estimated spatial spike locations and dominant spike shape features is exploited for fast and reliable clustering into single units. Millions of events can be sorted in minutes, and the method is parallelized and scales better than quadratically with the number of detected spikes. Performance is demonstrated using recordings with a 4,096-channel array and validated using anatomical imaging, optogenetic stimulation, and model-based quality control. A comparison with semi-automated, shape-based spike sorting exposes significant limitations of conventional methods. Our approach demonstrates that it is feasible to reliably isolate the activity of up to thousands of neurons and that dense, multi-channel probes substantially aid reliable spike sorting

Platelet activation is associated with myocardial infarction in patients with pneumonia

BACKGROUND: Troponins may be elevated in patients with pneumonia, but associations with myocardial infarction (MI) and with platelet activation are still undefined.OBJECTIVES: The aim of this study was to investigate the relationship between troponin elevation and in vivo markers of platelet activation in the early phase of hospitalization of patients affected by community-acquired pneumonia.METHODS: A total of 278 consecutive patients hospitalized for community-acquired pneumonia, who were followed up until discharge, were included. At admission, platelet activation markers such as plasma soluble P-selectin, soluble CD40 ligand, and serum thromboxane B2 (TxB2) were measured. Serum high-sensitivity cardiac troponin T levels and electrocardiograms were obtained every 12 and 24 h, respectively.RESULTS: Among 144 patients with elevated high-sensitivity cardiac troponin T, 31 had signs of MI and 113 did not. Baseline plasma levels of soluble P-selectin and soluble CD40 ligand and serum TxB2 were significantly higher in patients who developed signs of MI. Logistic regression analysis showed plasma soluble CD40 ligand (p < 0.001) and soluble P-selectin (p < 0.001), serum TxB2 (p = 0.030), mean platelet volume (p = 0.037), Pneumonia Severity Index score (p = 0.030), and ejection fraction (p = 0.001) to be independent predictors of MI. There were no significant differences in MI rate between the 123 patients (45%) taking aspirin (100 mg/day) and those who were not aspirin treated (12% vs. 10%; p = 0.649). Aspirin-treated patients with MIs had higher serum TxB2 compared with those without MIs (p = 0.005).CONCLUSIONS: MI is an early complication of pneumonia and is associated with in vivo platelet activation and serum TxB2 overproduction; aspirin 100 mg/day seems insufficient to inhibit thromboxane biosynthesis. (MACCE in Hospitalized Patients With Community-acquired Pneumonia; NCT01773863)

Coupled plasma filtration and adsorption (CPFA) for extracorporeal detoxification during acute or acute on chronic liver failure

INTRODUCTION: CPFA is currently used in the treatment of severe sepsis with the intention of removing the proinflammatory mediators from the systemic circulation. Some evidence exist about the bilirubin adsorbing ability of the neutral styrenic resin which is part of the extracorporeal circuit of CPFA. The aim of this study is to assess efficacy and safety of CPFA in extracorporeal detoxification of liver toxins in patients affected by acute or acute-on-chronic liver failure. METHODS: 9 patients (age 23 - 61 years) with acute (n = 3) or acute-on-chronic (n = 6) liver failure were enrolled. A total of 22 CPFA treatments were carried out. Each CPFA treatment lasted 6 hours. Unfractionated heparin was used as anticoagulation of the extracorporeal circuit in 7 patients; citrate anticoagulation with the concomitant infusion of calcium chloride in 2 of them. The number of treatment for each patient was established on his/her clinical status. The reduction ratios per session of bilirubin and bile acids were considered. Hemoglobin, platelets, white blood cells, coagulation tests, urea, creatinine, and electrolytes were also checked on starting CPFA and at the end of CPFA, as biocompatibility measures. RESULTS: All sessions were well tolerated by the patients. Alcohol was the most common etiology of the liver injury (n = 6), 1 patient was affected by acute cholangitis and Fisher-Evans syndrome, 1 had a viral etiology, and 1 patient had a postoperative jaundice. Median reduction rate per session for total bilirubin was 28% (range 2.2 – 40); for direct bilirubin was 31.4 (range 8.5 – 48.6); for indirect bilirubin was 29.1% (range 6.6 – 65); for bile acids was 30.6% (16.7 – 59.6); for lactic acid was 30% (range -57.2%-55.6%). In six out of nine patients was observed a recovery of liver function. At one year of follow-up 2 patients died during the hospitalization; 6 patients are followed like outpatients and 1 of them is no more in the waiting list for the transplant; the last one is in course of treatment. CONCLUSIONS: Although CPFA is a non-standardized technique for the liver depuration, its use in patients with acute or acute-on-chronic liver failure has shown favorable effects on safety and efficacy in terms of detoxification. Thus it is considerable a “bridge technique” toward the liver transplant and the recovery of basal liver function

Acute Myeloma Kidney: free light chains removal associated with chemotherapy for patients and kidney survival

INTRODUCTION. Renal failure remains a principal cause of morbidity and mortality for patient with multiple myeloma. Among renal manifestation casts nephropathy (Myeloma Kidney) represents the most common. The aim of this study is to assess the efficacy and safety of the extracorporeal removal of free light chains by means of hemodialysis with double filter application in patients with Acute Myeloma Kidney associated with different schemas of chemotherapy. METHODS. Fourteen patients (M/F = 11/ 3) were considered in the study. Acute Myeloma Kidney affected all these patients. Ten patients underwent renal biopsy and 9 cases of myeloma cast nephropathy were diagnosed. The median age of the patients was 72 years (range ). Every patient underwent the chemotherapy together with the extracorporeal treatment for the removal of free light chains by using double filter. Hemodialytic treatments were scheduled three times a week and the hemodialysis dose was not related to the degree of the renal failure but to the removal of free light chains. The dialysis filter used were characterized by high adsorbitive properties: PMMA filter (polymethylmetacrylate; Filtryzer BK-F 2.1 m2 surface area) cut-off 20,000 daltons; PEPA filter (polyester polymer alloy FDX 210-GW, 2.1 m2 surface area) cut-off 35,000 daltons. Each dialysis session lasted 4 hours. Low molecular weight heparin was used as anticoagulation. During each session two dialyzers were used and the substitution of the filter was carried out at the second hour of the hemodialysis session. For each session the reduction rate of free light chains was calculated. Urine output, hemoglobin, platelets, white blood cell, renal function and electrolytes were assessed. RESULTS. Average number of dialytic session was 10. Median Reduction Rate for free light chains was 25 % (range 2.4% - 69%). There was no statistical significant difference in FLC reduction rate between PEPA double filter and PMMA double filter (median reduction rate 53% vs. 38%). Six patient involved in the study died because of the complications of multiple myeloma (infections, bone fractures, chronic kidney disease). They all required chronic hemodialysis. Eight patients survived: among these 6 restored their renal function and 2 required chronic hemodialysis treatment. DISCUSSION. Early removal of free light chains in patient with renal involvement associated with specific chemotherapy is a predictive factor of recovery of renal function and that the recovery of renal function is associated to a best outcome of the patient. The use of an extracorporeal treatment based on substitution of filter at the second hour of the dialytic session was assessed. The two types of filters (PMMA and PEPA) didn’t show statistical differences