76
|
|
77
|
Garippa G, Varcasia A, Scala A. Cystic echinococcosis in Italy from the 1950s to present. PARASSITOLOGIA 2004; 46:387-91. [PMID: 16044697] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Subscribe] [Scholar Register] [Indexed: 05/03/2023]
Abstract
In Italy the epidemiological pattern of cistic echinococcosis (CE) is incomplete and the information for most regions is out of date, contradictory, and almost exclusively limited to the intermediate hosts. The disease is found most frequently in particular social and economic conditions: widespread use of extensive or semi-extensive sheep farming, illegal slaughtering, and high numbers of sheepdogs and other types of dogs. The highest incidence in sheep is found in Sardinia (70.6-92.8%), Sicily (6.5-36.5%), Basilicata (5-28%), Abruzzo (22%) and Tuscany (47%). It North Italy, it is never higher than 0.5% in slaughtered sheep. No data are available on the biomolecular characterization of the strains of E. granulosus in Italy, apart from Sardinia and recently Lazio. G1 (Sheep strain), G7 (Pig strain) G2 (Tasmanian sheep strain) have been identified in Sardinia and G1 and G3 (Buffalo strain) have been recently isolated in Lazio. In Italy, CE has was also found in buffaloes (2.63-9.8%) and horses (<1%). However, further epidemiological surveys and genotyping study are necessary. The small quantity of up to date information on the diffusion of E. granulosus in dogs (Abruzzo 4%, Sardinia 6-10% and Sicily 19.3%) highlights the need for modern, fast, sensitive and low risk diagnostic methods which would provide a true picture of the pattern of the infection in this host.
Collapse
|
78
|
Scala A, Canu S, Tanda B, Basciu M, Polinas L, Sanna Coccone GN, Pilloni S, Canu S, Varcasia A, Garippa G. An epidemiological and biomolecular survey of cystic echinococcosis in cattle in Sardinia. PARASSITOLOGIA 2004; 46:443-4. [PMID: 16044715] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [MESH Headings] [Subscribe] [Scholar Register] [Indexed: 05/03/2023]
|
79
|
Scala A, Varcasia A, Garippa G. Cystic echinococcosis in Sardinia: the current role of sheep. PARASSITOLOGIA 2004; 46:397-400. [PMID: 16044699] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Subscribe] [Scholar Register] [Indexed: 05/03/2023]
Abstract
Cystic echinococcosis is one of the most widespread parasitosis in the Mediterranean region. Unfortunately this is also true for Sardinia for various reasons, among which is the close relationship between sheep and dogs in the farms. This work first epidemiologically analyses hydatidosis in sheep in Sardinia and then examines the most important causes of the persistence of these metacestodosis in sheep. The work looks at the factors which are responsible for the enormous quantity of illegal slaughtering and the widespread habit of abandoning the sheep carcasses in the grazing areas, as well as possible initiatives which may eliminate these practices. Such initiatives must include reducing the financial costs and bureaucracy involved when sheep are slaughtered in abattoirs, and also increasing the value of sheep meat. In conclusion new checks and controls are hoped for at a political level which will increase the financial support for the farmers and encourage the use of recombinant vaccines which have already been tested in Sardinia. These are extremely useful for effectively curbing cystic echinococcosis.
Collapse
|
80
|
Varcasia A, Garippa G, Scala A. The diagnosis of Echinococcus granulosus in dogs. PARASSITOLOGIA 2004; 46:409-12. [PMID: 16044702] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Subscribe] [Scholar Register] [Indexed: 05/03/2023]
Abstract
The problem of diagnosing Echinococcus granulosus in dogs has still only been partially resolved, even after the advent of biotechnology. The eggs of taeniid Cestoda are extremely similar, and thus identification by microscopic examination of the faeces is risky and non-specific. For this reason, Echinococcus granulosus was traditionally diagnosed in dogs ante mortem after an arecoline hydrobromate purge. The faeces were examined macro and microscopically to establish if the adult tapeworm or its proglottids were present. Although this method is 100% specific, it is bio-hazardous and time-consuming, requires trained personnel, and its sensitivity varies. In the 1990s copro-antigens were discovered and characterised. These are released by the adult worm in the faeces. This made it possible to use enzyme-linked immune-adsorbent assay (ELISA) for in vitam diagnosis of Echinococcus granulosus. In recent years several PCR protocols have been published on the identification of Echinococcus granulosus DNA from eggs or from adult parasites and new ways of diagnosing this cestode have been developed.
Collapse
|
81
|
Cringoli G, Rinaldi L, Veneziano V, Capelli G, Scala A. The influence of flotation solution, sample dilution and the choice of McMaster slide area (volume) on the reliability of the McMaster technique in estimating the faecal egg counts of gastrointestinal strongyles and Dicrocoelium dendriticum in sheep. Vet Parasitol 2004; 123:121-31. [PMID: 15265576 DOI: 10.1016/j.vetpar.2004.05.021] [Citation(s) in RCA: 127] [Impact Index Per Article: 6.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/12/2004] [Revised: 04/23/2004] [Accepted: 05/06/2004] [Indexed: 11/18/2022]
Abstract
The present study was aimed to evaluate the influence of flotation solution, sample dilution, and the choice of McMaster slide area (volume) on the reliability of the McMaster technique in estimating the faecal egg counts of gastrointestinal (GI) strongyles and Dicrocoelium dendriticum in a composite sample of faeces from naturally infected sheep. Fourteen flotation solutions having densities between 1.200 and 1.450, and six sample dilutions, 1:10, 1:15, 1:20, 1:30, 1:40 and 1:50 were used. Each of the six dilutions was divided into 70 aliquots in order to have five replicates of each of the 14 flotation solutions at each of the six dilutions. For each McMaster slide, the GI strongyle and D. dendriticum egg counts were performed under one grid (McM 0.15 ml), two grids (McM 0.3 ml), one chamber (McM 0.5 ml), and both chambers (McM 1.0 ml). Mean eggs per gram (EPG) of faeces of GI strongyles and D. dendriticum were calculated and statistical analyses were performed on the resulting data. The type of flotation solution used significantly influenced the EPG in the GI strongyles and in the D. dendriticum egg counts. All the sucrose-based solutions at density between 1.200 and 1.350 floated more GI strongyle eggs than the others. With respect to D. dendriticum, only six solutions were capable of floating eggs and the potassium iodomercurate solution (density 1.440) floated more eggs than the others. The reliability of the McMaster technique regarding sample dilution was high for both GI strongyle and D. dendriticum EPG at 1:10 and 1:15, and then progressively decreased with increasing dilution. The reliability of the McMaster technique regarding the choice of the McMaster slide area (volume) was high for both GI strongyle and D. dendriticum EPG at the McMaster slide area (volume) of 1.0 ml, i.e. the total area of the McMaster slide. The EPG counts resulting from choosing any of the other three McMaster slide areas (volumes), i.e. McM 0.15 ml, McM 0.3 ml, or McM 0.5 ml, produced unreliable over-estimates. The findings of the present study show that the highest reliability of the McMaster technique for estimating GI strongyle and D. dendriticum egg counts in faeces from pastured sheep is obtained when using flotation solutions based on sucrose for GI strongyles, and potassium iodomercurate for D. dendriticum, dilutions which do not exceed 1:15, and the McMaster slide area (volume) of 1.0 ml.
Collapse
|
82
|
Garanin DA, Schilling R, Scala A. Saddle index properties, singular topology, and its relation to thermodynamic singularities for a phi4 mean-field model. PHYSICAL REVIEW. E, STATISTICAL, NONLINEAR, AND SOFT MATTER PHYSICS 2004; 70:036125. [PMID: 15524605 DOI: 10.1103/physreve.70.036125] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 03/31/2004] [Indexed: 05/24/2023]
Abstract
We investigate the potential energy surface of a phi(4) model with infinite range interactions. All stationary points can be uniquely characterized by three real numbers alpha(+) , alpha(0) , alpha(-) with alpha(+) + alpha(0) + alpha(-) =1 , provided that the interaction strength mu is smaller than a critical value. The saddle index n(s) is equal to alpha(0) and its distribution function has a maximum at n(max)(s) =1/3 . The density p (e) of stationary points with energy per particle e , as well as the Euler characteristic chi (e) , are singular at a critical energy e(c) (mu) , if the external field H is zero. However, e(c) (mu) not equal upsilon(c) (mu) , where upsilon(c) (mu) is the mean potential energy per particle at the thermodynamic phase transition point T(c) . This proves that previous claims that the topological and thermodynamic transition points coincide is not valid, in general. Both types of singularities disappear for H not equal 0 . The average saddle index n (s) as function of e decreases monotonically with e and vanishes at the ground state energy, only. In contrast, the saddle index n(s) as function of the average energy e ( n(s) ) is given by n(s) ( e ) =1+4 e (for H=0 ) that vanishes at e =-1/4> upsilon(0) , the ground state energy.
Collapse
|
83
|
Carta A, Scala A. [Recent findings on the genetics of gastro-intestinal nematode resistance in ruminants]. PARASSITOLOGIA 2004; 46:251-5. [PMID: 15305728] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Subscribe] [Scholar Register] [Indexed: 04/30/2023]
Abstract
The control of helminthiases in ruminants raised in open pasture has been mainly undertaken by using prophylactic measures in the environment, but these are often inadequate due to incorrect application. With the appearance of anthelmintics, the strategy for controlling these parasitoses, passed to pharmacological treatments which became effective in reducing their impact. However, the frequent and incorrect utilisation of these molecules resulted in resistance to anthelmintics and the presence of chemical residues in animal products for human consumption. Anthelmintic resistance is widespread throughout the world, heterogeneous and probably underestimated. This has encouraged the introduction of homeopathic agents and products derived from plants whose effectiveness has not been scientifically assessed. It is well known that it is possible to detect differences in resistance to the most important parasites between breeds. In Europe, it has been reported that some ovine autochthonous breeds, Scottish Blackface and Lacaune, showed higher resistance. The implementation of breeding strategies aimed at obtaining animals with naturally low susceptibility to nematode infestations could therefore play an increasingly important role. Standard animal breeding techniques have been largely successful in improving the performance of domestic animals in the last century. Standard quantitative selection requires field data on: i) individual phenotype performance; ii) expected covariance among animals due to blood relationship between them. The whole process of predicting the breeding value of animals in order to select subsequently the genetically superior parents of the next generation is entirely based on sophisticated computations (BLUP-animal model). In sheep, the main objective is always selecting for milk yield and sometimes, in addition, milk composition. However, due to the evolution of the EU agricultural policy and consumer demand in terms of healthy and organic food, more attention is now being given to traits related to health (resistance to EST, mastitis or parasitic diseases). Some studies conducted in New Zealand and Australia showed that nematode resistance is genetically controlled with high heritabilities and quite low genetic correlations with production traits. In this sense, some studies showed that it is possible to decrease the number of parasites in the framework of a traditional breeding programme. However, in most situations, this trait is not extensively recorded due to the high cost of individual recording. Therefore, it would be useful to implement breeding strategies based on the knowledge of the genes involved in this trait expression. Traditionally, two approaches are available to locate a gene: i) genome scan; ii) candidate gene approach. The candidate gene approach attempts to link general resistance to some particular genes. To date, genetic resistance against parasites is considered to be linked with the MHC and IgE genes. Furthermore, several gene detection studies based on the genome scan approach for this trait are currently being carried out on both crossed experimental populations (fat x lean Blackface lines and Sarda x Lacaune) and pure breeds (Churra). The preliminary results seem promising as to the use of marker assisted or genotype assisted selection for this trait, which is difficult and expensive to measure on a population scale.
Collapse
|
84
|
Scala A, Checchi L, Montevecchi M, Marini I, Giamberardino MA. Update on burning mouth syndrome: overview and patient management. CRITICAL REVIEWS IN ORAL BIOLOGY AND MEDICINE : AN OFFICIAL PUBLICATION OF THE AMERICAN ASSOCIATION OF ORAL BIOLOGISTS 2003; 14:275-91. [PMID: 12907696 DOI: 10.1177/154411130301400405] [Citation(s) in RCA: 321] [Impact Index Per Article: 15.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/17/2022]
Abstract
Burning Mouth Syndrome (BMS) is a chronic pain syndrome that mainly affects middle-aged/old women with hormonal changes or psychological disorders. This condition is probably of multifactorial origin, often idiopathic, and its etiopathogenesis remains largely enigmatic. The present paper discusses several aspects of BMS, updates current knowledge, and provides guidelines for patient management. There is no consensus on the diagnosis and classification of BMS. The etiopathogenesis seems to be complex and in a large number of patients probably involves interactions among local, systemic, and/or psychogenic factors. In the remaining cases, new interesting associations have recently emerged between BMS and either peripheral nerve damage or dopaminergic system disorders, emphasizing the neuropathic background in BMS. Based on these recent data, we have introduced the concepts of "primary" (idiopathic) and "secondary" (resulting from identified precipitating factors) BMS, since this allows for a more systematic approach to patient management. The latter starts with a differential diagnosis based on the exclusion of both other orofacial chronic pain conditions and painful oral diseases exhibiting muco-sal lesions. However, the occurrence of overlapping/overwhelming oral mucosal pathologies, such as infections, may cause difficulties in the diagnosis ("complicated BMS"). BMS treatment is still unsatisfactory, and there is no definitive cure. As a result, a multidisciplinary approach is required to bring the condition under better control. Importantly, BMS patients should be offered regular follow-up during the symptomatic periods and psychological support for alleviating the psychogenic component of the pain. More research is necessary to confirm the association between BMS and systemic disorders, as well as to investigate possible pathogenic mechanisms involving potential nerve damage. If this goal is to be achieved, a uniform definition of BMS and strict criteria for its classification are mandatory.
Collapse
|
85
|
Di Bonito P, Di Fraia L, Di Gennaro L, Russo P, Scala A, Iovine C, Vaccaro O, Capaldo B. Impact of known and unknown diabetes on in-hospital mortality from ischemic stroke. Nutr Metab Cardiovasc Dis 2003; 13:148-153. [PMID: 12955796 DOI: 10.1016/s0939-4753(03)80174-6] [Citation(s) in RCA: 11] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/15/2022]
Abstract
BACKGROUND AND AIMS The effect of known diabetes on in-hospital mortality from ischemic stroke is still debated whereas the role of unknown diabetes is virtually unexplored. This study evaluates the impact of known and unknown diabetes on in-hospital mortality from ischemic stroke. METHODS AND RESULTS We have retrospectively evaluated the records of 286 consecutive cases of ischemic stroke hospitalized from January 1998 to December 2000 at the Department of Internal Medicine of the General Hospital located in the western area of Naples. Fasting plasma glucose level < 7 mmol/L identified non diabetic subjects. Known diabetes mellitus was diagnosed by history of diabetes and/or hypoglycemic therapy, unknown diabetes was defined as a random plasma glucose level > or = 11 mmol/L and/or in-hospital fasting glucose > or = 7 mmol/L on two or more occasions. Severity of stroke was defined using the Canadian Neurological Score (CNS). According to these criteria, 144 subjects were non diabetics, 99 had known diabetes and 43 had unknown diabetes. Subjects with known diabetes showed a higher prevalence of female sex, hypertension and increased triglyceride levels as compared with non diabetic subjects (p < 0.01). Subjects with unknown diabetes were older (p < 0.01) and showed a more severe CNS (3.4 +/- 2.7) than non diabetic and diabetic subjects (5.8 +/- 2.6 and 5.8 +/- 2.6, respectively; p < 0.01). In-hospital mortality was significantly higher in the unknown diabetic group (44%) as compared with known diabetic (15%) and non diabetic groups (12%) (p < 0.001). This finding was independent of neurological deficit, age, atrial fibrillation and history of previous stroke. CONCLUSIONS Our study shows that unknown diabetes, more than known diabetes, is a strong risk factor for in-hospital mortality in subjects with acute ischemic stroke.
Collapse
|
86
|
Angelani L, Di Leonardo R, Ruocco G, Scala A, Sciortino F. Reply to “Comment on ‘Quasisaddles as relevant points of the potential energy surface in the dynamics of supercooled liquids’ ” [J. Chem. Phys. 118, 5263 (2002)]. J Chem Phys 2003. [DOI: 10.1063/1.1553755] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/15/2022] Open
|
87
|
Sánchez-Andrade R, Paz-Silva A, Suárez JL, Arias M, López C, Morrondo P, Scala A. Serum antibodies to Dicrocoelium dendriticum in sheep from Sardinia (Italy). Prev Vet Med 2003; 57:1-5. [PMID: 12547170 DOI: 10.1016/s0167-5877(02)00215-5] [Citation(s) in RCA: 16] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/23/2022]
Abstract
An indirect enzyme-linked immunosorbent assay (ELISA) with Dicrocoelium dendriticum excretory/secretory antigens was used to evaluate the presence of serum antibodies against the trematode in 738 sheep randomly chosen in Sardinia (Italy). Coprological sedimentation was used to discover egg-output. Seropositivity was detected in 86.2% tested sheep, whereas faecal prevalence was 6.7%; all that were faecal-positive also were ELISA-positive.
Collapse
|
88
|
Poglayen G, Giannetto S, Scala A, Garippa G, Capelli G, Scaravelli D, Brianti E, Reeve NJ. Helminths found in hedgehogs (Erinaceus europaeus) in three areas of Italy. Vet Rec 2003; 152:22-4. [PMID: 12542271 DOI: 10.1136/vr.152.1.22] [Citation(s) in RCA: 15] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/04/2022]
|
89
|
Sciortino F, La Nave E, Scala A, Stanley HE, Starr FW. Water and its energy landscape. THE EUROPEAN PHYSICAL JOURNAL. E, SOFT MATTER 2002; 9:233-237. [PMID: 15010913 DOI: 10.1140/epje/i2002-10080-6] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/24/2023]
Abstract
We present an overview of the recent studies on the properties of the potential energy surface for a simple model of water. We emphasize the relations between PES properties and dynamics in supercooled states for the model and discuss possible future application of the PES studies.
Collapse
|
90
|
Scala A, Paz-Silva A, Suárez JL, López C, Díaz P, Díez-Baños P, Sánchez-Andrade Fernández R. Chronobiology of Oestrus ovis (Diptera: Oestridae) in Sardinia, Italy: guidelines to chemoprophylaxis. JOURNAL OF MEDICAL ENTOMOLOGY 2002; 39:652-657. [PMID: 12144298 DOI: 10.1603/0022-2585-39.4.652] [Citation(s) in RCA: 15] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/23/2023]
Abstract
Oestrus ovis (Linné 1761) larvae are obligatory parasites of the nasal and sinus cavities of sheep and goats. Infestation is prevalent in hot and dry regions, such as Mediterranean countries. The current work was developed to establish the chronobiology of O. ovis in Sardinia, to determine the most suitable time for chemoprophylaxis. A survey was carried out during 1998, and sheep heads were collected monthly from local flocks. A total of 443 heads was examined, and the prevalence of oestrosis was 73.8%. We collected 2,691 larvae (mean = 6.07 +/- 9.52), and the intensity was greatest in November. The humoral immune response against the nasal bot fly was analyzed by means of an indirect-ELISA using second-instar O. ovis excretory and secretory antigens. A seasonal variation in the antibody levels was observed, increasing from April and peaked in June and in September. A significant correlation was observed between first instar intensity and the mean relative humidity (r2 = 0.120; P < 0.05), and between second-instar intensity and the mean temperature (r2 = 0.241; P < 0.05). Three periods in the chronobiology of O. ovis were defined: diapause (October-February), the active phase ofthe endogenous cycle (March-September) and the exit phase (May-September). Our results showed that treatment in October-November was suitable, because first instars were in diapause, preventing the development of first into second instars, and second into third instars.
Collapse
|
91
|
Angelani L, Di Leonardo R, Ruocco G, Scala A, Sciortino F. Quasisaddles as relevant points of the potential energy surface in the dynamics of supercooled liquids. J Chem Phys 2002. [DOI: 10.1063/1.1475764] [Citation(s) in RCA: 48] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/14/2022] Open
|
92
|
|
93
|
Allevi P, Anastasia M, Ciuffreda P, Fiecchi A, Scala A. Simple transformation of carminic acid into kermesic acid. J Org Chem 2002. [DOI: 10.1021/jo00233a033] [Citation(s) in RCA: 14] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
|
94
|
Scala A, Solinas G, Citterio CV, Kramer LH, Genchi C. Sheep oestrosis (Oestrus ovis Linné 1761, Diptera: Oestridae) in Sardinia, Italy. Vet Parasitol 2001; 102:133-41. [PMID: 11705659 DOI: 10.1016/s0304-4017(01)00515-5] [Citation(s) in RCA: 38] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Abstract
Oestrosis, the nasal myiasis of sheep and goats, is caused by the larvae of Oestrus ovis L. 1758 (Diptera, Oestridae) that develop from the first to the third stage larva in the nasal cavities and frontal sinuses of affected animals. The authors report the results of an epidemiological study of oestrosis of sheep in Sardinia, Italy. Heads of 6-month to 10-year-old Sardinian sheep (n=566) from 124 free-ranging flocks were examined for the presence and location O. ovis larvae from December 1996 to November 1997. Larvae were collected, counted, and larval stages were identified. O. ovis larvae were found in 100% of examined flocks and in 91% (514/566) of examined sheep. The monthly prevalence ranged from 69% in May to 100% in July. First stage larvae were found in 82% (463) of all heads examined, second stage larvae in 65% (367) and third stage larvae in 10% (56). The majority of sheep harboured first stage larvae, with prevalences of over 80% throughout most of the study period. The prevalence of O. ovis found in this study of Sardinian sheep is the highest reported in the Mediterranean area. The high percentage of first stage larvae found throughout the entire study period may be due to a brief period of decreased rate of larval maturation, in particular in December 1996 (96%) and January-October 1997 (94%). Third stage larvae were consistently present, often however, with extremely low prevalences compared to total larval burden.
Collapse
|
95
|
La Nave E, Scala A, Starr FW, Stanley HE, Sciortino F. Dynamics of supercooled water in configuration space. PHYSICAL REVIEW. E, STATISTICAL, NONLINEAR, AND SOFT MATTER PHYSICS 2001; 64:036102. [PMID: 11580389 DOI: 10.1103/physreve.64.036102] [Citation(s) in RCA: 18] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 02/01/2001] [Indexed: 05/23/2023]
Abstract
We study the potential energy surface (PES) sampled by a liquid modeled via the widely studied extended simple point charge (SPC/E) model for water. We characterize the curvature of the PES by calculating the instantaneous normal mode (INM) spectrum for a wide range of densities and temperatures. We discuss the information contained in the INM density of states, which requires additional processing to be unambiguously associated with the long-time dynamics. For the SPC/E model, we find that the slowing down of the dynamics in the supercooled region-where the ideal mode coupling theory has been used to describe the dynamics-is controlled by the reduction in the number of directions in configuration space that allow a structural change. We find that the fraction f(dw) of the double-well directions in configuration space determines the value of the diffusion constant D, thereby relating a property of the PES to a macroscopic dynamic quantity; specifically, it appears that square root D is approximately linear in f(dw). Our findings are consistent with the hypothesis that, at the mode coupling crossover temperature, dynamical processes based on the free exploration of configuration space vanish, and processes requiring activation dominate. Hence, the reduction of the number of directions allowing free exploration of configuration space is the mechanism of diffusion implicitly implemented in the ideal mode coupling theory. Additionally, we find a direct relationship between the number of basins sampled by the system and the number of free directions. In this picture, diffusion appears to be related to geometrical properties of the PES, and to be entropic in origin.
Collapse
|
96
|
Colombo D, Compostella F, Ronchetti F, Scala A, Tokuda H, Nishino H. Diesters of glycosylglycerols active in cancer chemoprevention. Eur J Med Chem 2001; 36:691-5. [PMID: 11600238 DOI: 10.1016/s0223-5234(01)01261-2] [Citation(s) in RCA: 18] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/19/2022]
Abstract
Enzymatic transesterification, mediated by Pseudomonas cepacia lipase (lipase PS), led to the pure 1,6'-diacylderivatives of 2-O-beta-D-glucosyl-sn-glycerol and 2-O-beta-D-galactosyl-sn-glycerol, the acyl chains being derived from short-medium length fatty acids. A study of the in vitro inhibitory effects of these diacylderivatives on Epstein-Barr virus early antigen activation induced by the tumour promoter 12-O-tetradecanoylphorbol-13-acetate revealed that maximum activity was reached for the hexanoyl chain and that the introduction of a second acyl chain did not significantly modify the inhibitory potential referring to the corresponding 1- or 6'-monoesters.
Collapse
|
97
|
Scala A, Sadr-Lahijany MR, Giovambattista N, Buldyrev SV, Stanley HE. Waterlike anomalies for core-softened models of fluids: two-dimensional systems. PHYSICAL REVIEW. E, STATISTICAL, NONLINEAR, AND SOFT MATTER PHYSICS 2001; 63:041202. [PMID: 11308830 DOI: 10.1103/physreve.63.041202] [Citation(s) in RCA: 40] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 10/13/2000] [Indexed: 05/23/2023]
Abstract
We use molecular-dynamics simulations in two dimensions to investigate the possibility that a core-softened potential can reproduce static and dynamic anomalies found experimentally in liquid water: (i) the increase in specific volume upon cooling, (ii) the increase in isothermal compressibility upon cooling, and (iii) the increase in the diffusion coefficient with pressure. We relate these anomalies to the shape of the potential. We obtain the phase diagram of the system and identify two solid phases: a square crystal (high-density phase) and a triangular crystal (low-density phase). We also discuss the relation between the anomalies observed and the polymorphism of the solid. Finally, we compare the phase diagram of our model system with experimental data, noting especially the line of temperatures of maximum density, the line of pressures of maximum diffusion constant, and the line of temperatures of minimum isothermal compressibility.
Collapse
|
98
|
Starr FW, Sastry S, La Nave E, Scala A, Stanley HE, Sciortino F. Thermodynamic and structural aspects of the potential energy surface of simulated water. PHYSICAL REVIEW E 2001; 63:041201. [PMID: 11308829 DOI: 10.1103/physreve.63.041201] [Citation(s) in RCA: 77] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 07/28/2000] [Indexed: 11/07/2022]
Abstract
Relations between the thermodynamics and dynamics of supercooled liquids approaching a glass transition is a topic of considerable interest. The potential energy surface of model liquids has been increasingly studied, since it provides a connection between the configurational component of the partition function on the one hand, and the system dynamics on the other. This connection is most obvious at low temperatures, where the motion of the system can be partitioned into vibrations within a basin of attraction and infrequent interbasin transitions. In this work, we present a description of the potential energy surface properties of supercooled liquid water. The dynamics of this model have been studied in great detail in recent years. We locate the minima sampled by the liquid by "quenches" from equilibrium configurations generated via molecular dynamics simulations, and then calculate the temperature and density dependence of the basin energy, degeneracy, and shape. The temperature dependence of the energy of the minima is qualitatively similar to simple liquids, but has anomalous density dependence. The unusual density dependence is also reflected in the configurational entropy, the thermodynamic measure of degeneracy. Finally, we study the structure of simulated water at the minima, which provides insight on the progressive tetrahedral ordering of the liquid on cooling.
Collapse
|
99
|
Scala A, Dokholyan NV, Buldyrev SV, Stanley HE. Thermodynamically important contacts in folding of model proteins. PHYSICAL REVIEW E 2001; 63:032901. [PMID: 11308693 DOI: 10.1103/physreve.63.032901] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 10/13/2000] [Indexed: 11/07/2022]
Abstract
We introduce a quantity, the entropic susceptibility, that measures the thermodynamic importance-for the folding transition-of the contacts between amino acids in model proteins. Using this quantity, we find that only one equilibrium run of a computer simulation of a model protein is sufficient to select a subset of contacts that give rise to the peak in the specific heat observed at the folding transition. To illustrate the method, we identify thermodynamically important contacts in a model 46-mer. We show that only about 50% of all contacts present in the protein native state are responsible for the sharp peak in the specific heat at the folding transition temperature, while the remaining 50% of contacts do not affect the specific heat.
Collapse
|
100
|
Lanni G, Napolitano MM, Scala A, De Rosa P. "Tube-guided" implant of bioprosthetic shunt for hemodialysis. Am J Surg 2001; 181:50-1. [PMID: 11248176 DOI: 10.1016/s0002-9610(00)00527-4] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/18/2022]
Abstract
Implant of a bovine-derived vascular bioprosthesis as arterio-venous shunt for hemodialysis may raise some problems regarding tunnel fashioning. Therefore, we have proposed a simple "tube-guided" technique to make implant safer and to avoid complications.
Collapse
|