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1.
J Anim Ecol ; 90(5): 1228-1238, 2021 05.
Article in English | MEDLINE | ID: mdl-33786863

ABSTRACT

Long-distance migrations are among the most physically demanding feats animals perform. Understanding the potential costs and benefits of such behaviour is a fundamental question in ecology and evolution. A hypothetical cost of migration should be outweighed by higher productivity and/or higher annual survival, but few studies on migratory species have been able to directly quantify patterns of survival throughout the full annual cycle and across the majority of a species' range. Here, we use telemetry data from 220 migratory Egyptian vultures Neophron percnopterus, tracked for 3,186 bird months and across approximately 70% of the species' global distribution, to test for differences in survival throughout the annual cycle. We estimated monthly survival probability relative to migration and latitude using a multi-event capture-recapture model in a Bayesian framework that accounted for age, origin, subpopulation and the uncertainty of classifying fates from tracking data. We found lower survival during migration compared to stationary periods (ß = -0.816; 95% credible interval: -1.290 to -0.318) and higher survival on non-breeding grounds at southern latitudes (<25°N; ß = 0.664; 0.076-1.319) compared to on breeding grounds. Survival was also higher for individuals originating from Western Europe (ß = 0.664; 0.110-1.330) as compared to further east in Europe and Asia, and improved with age (ß = 0.030; 0.020-0.042). Anthropogenic mortalities accounted for half of the mortalities with a known cause and occurred mainly in northern latitudes. Many juveniles drowned in the Mediterranean Sea on their first autumn migration while there were few confirmed mortalities in the Sahara Desert, indicating that migration barriers are likely species-specific. Our study advances the understanding of important fitness trade-offs associated with long-distance migration. We conclude that there is lower survival associated with migration, but that this may be offset by higher non-breeding survival at lower latitudes. We found more human-caused mortality farther north, and suggest that increasing anthropogenic mortality could disrupt the delicate migration trade-off balance. Research to investigate further potential benefits of migration (e.g. differential productivity across latitudes) could clarify how migration evolved and how migrants may persist in a rapidly changing world.


Subject(s)
Animal Migration , Birds , Africa, Northern , Animals , Bayes Theorem , Europe , Mediterranean Sea , Seasons
2.
J Chem Phys ; 155(4): 044903, 2021 Jul 28.
Article in English | MEDLINE | ID: mdl-34340383

ABSTRACT

We study theoretically the effect of size difference and that of gravity in the phase behavior of a binary mixture of patchy particles. The species, 2A and 3B, have two A and three B patches, respectively, and only bonds between patches A and B (AB bonds) are allowed. This model describes colloidal systems where the aggregation of particles (3B) is mediated and controlled by a second species, the linkers (2A) to which they bind strongly. Thermodynamic calculations are performed using Wertheim's perturbation theory with a hard sphere reference term that accounts for the difference in the size of the two species. Percolation lines are determined employing a generalized Flory-Stockmayer theory, and the effects of gravity are included through a local density approximation. The bulk phase diagrams are calculated, and all the stacking sequences generated in the presence of gravity are determined and classified in a stacking diagram. The relative size of the particles can be used to control the phase behavior of the mixture. An increase in the size of particles 3B, relative to the size of the linkers 2A, is found to promote mixing while keeping the percolating structures and, in certain cases, leads to changes in the stacking sequence under gravity.

3.
J Sports Sci ; 38(11-12): 1269-1278, 2020.
Article in English | MEDLINE | ID: mdl-32378447

ABSTRACT

Talent identification (TID) and development (TDE) are large fields in professional soccer and in science. However,  TID and TDE processes in youth academies have not been assessed in detail. As such, our aim was to survey professional clubs from around the world about their youth academy TID and TDE processes, with 29 clubs responding to the survey. TID and TDE processes changed as a function of player age. TID processes involved finding the best players locally and regionally, but for older players the search widened to nationally and internationally for the needs of the first team. Clubs used a multidisciplinary approach to TID, but more so with older players. Median number of academy players was 80, 100, and 66 players at 8-11 years, 12-16 years, and 17-21 years, respectively. Annual player turnover in the most recent season (selections/de-selections) was 29% across all age groups, with competition from other clubs cited as a limitation to TID. TDE processes involved weekly matches and 3-5 training sessions per week led by experienced, well-qualified coaches, with most clubs providing players with academic education, residency and transportation services. Our findings extend previous research assessing professional soccer youth academy TID and TDE processes by quantifying worldwide practices.


Subject(s)
Aptitude , Athletic Performance/physiology , Mentoring , Soccer/physiology , Adolescent , Child , Decision Making , Education , Housing , Humans , Male , Physical Conditioning, Human , Program Development , Young Adult
4.
Soft Matter ; 13(43): 7870-7878, 2017 Nov 08.
Article in English | MEDLINE | ID: mdl-29019510

ABSTRACT

We employ a method based on Monte Carlo grand-canonical simulations to precisely calculate partition functions of non-interacting chains and rings formed by dipolar hard spheres (DHS) at low temperature. The extended low temperature region offered by such cluster calculations, compared to what had been previously achieved with standard simulations, opens up the possibility of exploring a part of the DHS phase diagram which was inaccessible before. The reported results offer the unique opportunity of verifying well-established theoretical models based on the ideal gas of cluster approximation in order to clarify their range of validity. They also provide the basis for future studies in which cluster-cluster interactions will be included.

5.
J Chem Phys ; 146(4): 041103, 2017 01 28.
Article in English | MEDLINE | ID: mdl-28147524

ABSTRACT

A re-entrant gas-liquid spinodal was proposed as a possible explanation of the apparent divergence of the compressibility and specific heat off supercooling water. Such a counter-intuitive possibility, e.g., a liquid that becomes unstable to gas-like fluctuations on cooling at positive pressure, has never been observed, neither in real substances nor in off-lattice simulations. More recently, such a re-entrant scenario has been dismissed on the premise that the re-entrant spinodal would collide with the gas-liquid coexisting curve (binodal) in the pressure-temperature plane. Here we study, numerically and analytically, two previously introduced one-component patchy particle models that both show (i) a re-entrant limit of stability of the liquid phase and (ii) a re-entrant binodal, providing a neat in silico (and in charta) realization of such unconventional thermodynamic scenario.

6.
Molecules ; 22(11)2017 Nov 15.
Article in English | MEDLINE | ID: mdl-29140265

ABSTRACT

Inflammation is a reaction of the host to infectious or sterile stimuli and has the physiological purpose of restoring tissue homeostasis. However, uncontrolled or unresolved inflammation can lead to tissue damage, giving rise to a plethora of chronic inflammatory diseases, including metabolic syndrome and autoimmunity pathologies with eventual loss of organ function. Beta-nitrostyrene and its derivatives are known to have several biological activities, including anti-edema, vasorelaxant, antiplatelet, anti-inflammatory, and anticancer. However, few studies have been carried out regarding the anti-inflammatory effects of this class of compounds. Thereby, the aim of this study was to evaluate the anti-inflammatory activity of 1-nitro-2-phenylethene (NPe) using in vitro and in vivo assays. Firstly, the potential anti-inflammatory activity of NPe was evaluated by measuring TNF-α produced by human macrophages stimulated with lipopolysaccharide (LPS). NPe at non-toxic doses opposed the inflammatory effects induced by LPS stimulation, namely production of the inflammatory cytokine TNF-α and activation of NF-κB and ERK pathways (evaluated by phosphorylation of inhibitor of kappa B-alpha [IκB-α] and extracellular signal-regulated kinase 1/2 [ERK1/2], respectively). In a well-established model of acute pleurisy, pretreatment of LPS-challenged mice with NPe reduced neutrophil accumulation in the pleural cavity. This anti-inflammatory effect was associated with reduced activation of NF-κB and ERK1/2 pathways in NPe treated mice as compared to untreated animals. Notably, NPe was as effective as dexamethasone in both, reducing neutrophil accumulation and inhibiting ERK1/2 and IκB-α phosphorylation. Taken together, the results suggest a potential anti-inflammatory activity for NPe via inhibition of ERK1/2 and NF-κB pathways on leukocytes.


Subject(s)
Anti-Inflammatory Agents/administration & dosage , Lipopolysaccharides/immunology , Pleurisy/drug therapy , Styrenes/administration & dosage , Tumor Necrosis Factor-alpha/metabolism , Animals , Anti-Inflammatory Agents/chemistry , Anti-Inflammatory Agents/pharmacology , Cell Line , Disease Models, Animal , Gene Expression Regulation/drug effects , Humans , MAP Kinase Signaling System/drug effects , Macrophages/drug effects , Macrophages/immunology , Mice , Molecular Structure , NF-kappa B/metabolism , Phosphorylation , Pleurisy/etiology , Pleurisy/metabolism , Styrenes/chemistry , Styrenes/pharmacology , THP-1 Cells
7.
Phys Chem Chem Phys ; 17(25): 16601-8, 2015 Jul 07.
Article in English | MEDLINE | ID: mdl-26054621

ABSTRACT

With the help of a unique combination of density functional theory and computer simulations, we discover two possible scenarios, depending on concentration, for the hierarchical self-assembly of magnetic nanoparticles on cooling. We show that typically considered low temperature clusters, i.e. defect-free chains and rings, merge into more complex branched structures through only three types of defects: four-way X junctions, three-way Y junctions and two-way Z junctions. Our accurate calculations reveal the predominance of weakly magnetically responsive rings cross-linked by X defects at the lowest temperatures. We thus provide a strategy to fine-tune magnetic and thermodynamic responses of magnetic nanocolloids to be used in medical and microfluidics applications.

8.
Phys Rev Lett ; 111(16): 168302, 2013 Oct 18.
Article in English | MEDLINE | ID: mdl-24182307

ABSTRACT

We study the interplay between phase separation and self-assembly in chains, rings, and branched structures in a model of particles with dissimilar patches. We extend Wertheim's first order perturbation theory to include the effects of ring formation and to theoretically investigate the thermodynamics of the model. We find a peculiar shape for the vapor-liquid coexistence, featuring reentrant behavior in both phases and two critical points, despite the single-component nature of the system. The emergence of the lower critical point is caused by the self-assembly of rings taking place in the vapor, generating a phase with lower energy and lower entropy than the liquid. Monte Carlo simulations of the same model fully support these unconventional theoretical predictions.

9.
Phys Rev Lett ; 110(14): 148306, 2013 Apr 05.
Article in English | MEDLINE | ID: mdl-25167048

ABSTRACT

We investigate, via numerical simulations, mean field, and density functional theories, the magnetic response of a dipolar hard sphere fluid at low temperatures and densities, in the region of strong association. The proposed parameter-free theory is able to capture both the density and temperature dependence of the ring-chain equilibrium and the contribution to the susceptibility of a chain of generic length. The theory predicts a nonmonotonic temperature dependence of the initial (zero field) magnetic susceptibility, arising from the competition between magnetically inert particle rings and magnetically active chains. Monte Carlo simulation results closely agree with the theoretical findings.

10.
J Chem Phys ; 139(13): 134901, 2013 Oct 07.
Article in English | MEDLINE | ID: mdl-24116579

ABSTRACT

In this contribution, we investigate the low-temperature, low-density behaviour of dipolar hard-sphere (DHS) particles, i.e., hard spheres with dipoles embedded in their centre. We aim at describing the DHS fluid in terms of a network of chains and rings (the fundamental clusters) held together by branching points (defects) of different nature. We first introduce a systematic way of classifying inter-cluster connections according to their topology, and then employ this classification to analyse the geometric and thermodynamic properties of each class of defects, as extracted from state-of-the-art equilibrium Monte Carlo simulations. By computing the average density and energetic cost of each defect class, we find that the relevant contribution to inter-cluster interactions is indeed provided by (rare) three-way junctions and by four-way junctions arising from parallel or anti-parallel locally linear aggregates. All other (numerous) defects are either intra-cluster or associated to low cluster-cluster interaction energies, suggesting that these defects do not play a significant part in the thermodynamic description of the self-assembly processes of dipolar hard spheres.


Subject(s)
Cold Temperature , Particulate Matter , Monte Carlo Method
11.
J Chem Phys ; 138(16): 164904, 2013 Apr 28.
Article in English | MEDLINE | ID: mdl-23635168

ABSTRACT

We investigate the phase behaviour of 2D mixtures of bi-functional and three-functional patchy particles and 3D mixtures of bi-functional and tetra-functional patchy particles by means of Monte Carlo simulations and Wertheim theory. We start by computing the critical points of the pure systems and then we investigate how the critical parameters change upon lowering the temperature. We extend the successive umbrella sampling method to mixtures to make it possible to extract information about the phase behaviour of the system at a fixed temperature for the whole range of densities and compositions of interest.


Subject(s)
Molecular Dynamics Simulation , Monte Carlo Method , Particle Size , Temperature
12.
Biodivers Data J ; 11: e100521, 2023.
Article in English | MEDLINE | ID: mdl-38327365

ABSTRACT

The current work presents the preliminary results of the Cinereous Vulture (Aegypiusmonachus) releases in the Balkan Mountains in 2018-2022, aiming at the species re-introduction in Bulgaria, where it was listed as locally extinct since 1985. The first imports and releases of Cinereous Vultures in Bulgaria started in 2018. Until mid-2022, 72 individuals were released in the Eastern Balkan Mountains (Kotlenska Planina SPA and Sinite Kamani Nature Park) and Vrachanski Balkan Nature Park. Of them, 63 immatures imported from Spain were released from aviaries and nine juveniles captive-bred in European zoos were released by hacking (fledging from an artificial nest). We compared the success in survival and establishment between the different release sites and methods used to adjust the ongoing technics and tactics and to support knowledge improvement for future similar projects. From the nine Cinereous Vultures released by hacking, the results were as follows: 1.00 fledging success, but only 0.22 survival in the first six months - combined period of acclimation, first migration and the first winter. All survivors from that period reached maturity into the wild, but all emigrated from the release site and settled elsewhere. Of the 63 individuals released by aviaries, 32 individuals were released in the Eastern Balkan Mountains (18 individuals are still alive - 0.56 survival; 14 individuals settled in the area, which accounts for 0.44 of all released birds and 0.78 of the survivors). Thirty-one individuals were released in Vrachanski Balkan Nature Park (23 individuals are still alive - 0.74 survival; 22 individuals settled in the area - 0.71 of all released birds and 0.96 of the survivors). Based only on aviary method comparison, the settling of the individuals in the release area was alike in the two sites. However, the Vrachanski Balkan Nature Park performed better in survival - both in acclimation and establishment periods. While comparing the release methods - hacking and release from the aviary - the following results were observed: the survival rate during acclimation was 0.86. Due to more considerable losses during the first migration and dispersal in the individuals released by hacking, the survival rate of 0.22 was significantly lower compared to 0.73 for the birds released from the aviary. Additionally, in both methods, a similar pattern in the first winter and spring migration dispersal was observed. Although the survival was equal in the released-by-hacking or aviary birds after the first year onwards, it is essential to note that the emigration of the hacked birds from the release site was 1.00. In comparison, the birds released from aviaries largely remained and settled in the release area (> 0.77 of the survivors). The cost of release and related acclimation, settling, dispersal and the first winter was the greatest: 0.12-0.17 per period, or cumulatively, it was about 0.27. Survival increased and stabilised to > 0.90 after the first year in the wild and reached nearly 1.00 after two years in the wild onwards. Two distinct nuclei of the Cinereous Vulture were established along the Balkan Mountains - the Eastern Balkan Mountains with 18-23 individuals and four formed pairs using a territory of about 642.74 km2 - 95% home range and 85.72 km2 - 50% core area with center being the town of Kotel; and Vrachanski Balkan Nature Park with present 23-29 individuals, of which 2-3 pairs formed so far, using a territory of about 1,143.66 km2 - 95% home range and 22.89 km2 - 50% core area with center being the village of Zgorigrad. The species readily accepted breeding in artificial nest platforms built by professional arborists on different tree species - oak, beech, sycamore and pine. The only naturally built nests were on the ground (n = 2) (unsuccessful) and in Scots Pine (n = 1) (successful). In 2021 and 2022, in each of the two sites, the first successful reproductions were recorded, which marked the return of the Cinereous Vulture as breeding species - 28 years after the last occasional record of a single breeding pair in the country and 36 years after it was officially listed as locally extinct in Bulgaria.

13.
J Cardiovasc Dev Dis ; 10(3)2023 Feb 27.
Article in English | MEDLINE | ID: mdl-36975867

ABSTRACT

BACKGROUND: Although several studies suggest that heparins prevent arrhythmias caused by acute myocardial infarction (AMI), the molecular mechanisms involved remain unclear. To investigate the involvement of pharmacological modulation of adenosine (ADO) signaling in cardiac cells by a low-molecular weight heparin (enoxaparin; ENOX) used in AMI therapy, the effects of ENOX on the incidences of ventricular arrhythmias (VA), atrioventricular block (AVB), and lethality (LET) induced by cardiac ischemia and reperfusion (CIR) were evaluated, with or without ADO signaling blockers. METHODS: To induce CIR, adult male Wistar rats were anesthetized and subjected to CIR. Electrocardiogram (ECG) analysis was used to evaluate CIR-induced VA, AVB, and LET incidence, after treatment with ENOX. ENOX effects were evaluated in the absence or presence of an ADO A1-receptor antagonist (DPCPX) and/or an inhibitor of ABC transporter-mediated cAMP efflux (probenecid, PROB). RESULTS: VA incidence was similar between ENOX-treated (66%) and control rats (83%), but AVB (from 83% to 33%) and LET (from 75% to 25%) incidences were significantly lower in rats treated with ENOX. These cardioprotective effects were blocked by either PROB or DPCPX. CONCLUSION: These results indicate that ENOX was effective in preventing severe and lethal arrhythmias induced by CIR due to pharmacological modulation of ADO signaling in cardiac cells, suggesting that this cardioprotective strategy could be promising in AMI therapy.

14.
Pharmaceuticals (Basel) ; 16(10)2023 Oct 16.
Article in English | MEDLINE | ID: mdl-37895945

ABSTRACT

Acute myocardial infarction (AMI) is the main cause of morbidity and mortality worldwide and is characterized by severe and fatal arrhythmias induced by cardiac ischemia/reperfusion (CIR). However, the molecular mechanisms involved in these arrhythmias are still little understood. To investigate the cardioprotective role of the cardiac Ca2+/cAMP/adenosine signaling pathway in AMI, L-type Ca2+ channels (LTCC) were blocked with either nifedipine (NIF) or verapamil (VER), with or without A1-adenosine (ADO), receptors (A1R), antagonist (DPCPX), or cAMP efflux blocker probenecid (PROB), and the incidence of ventricular arrhythmias (VA), atrioventricular block (AVB), and lethality (LET) induced by CIR in rats was evaluated. VA, AVB and LET incidences were evaluated by ECG analysis and compared between control (CIR group) and intravenously treated 5 min before CIR with NIF 1, 10, and 30 mg/kg and VER 1 mg/kg in the presence or absence of PROB 100 mg/kg or DPCPX 100 µg/kg. The serum levels of cardiac injury biomarkers total creatine kinase (CK) and CK-MB were quantified. Both NIF and VER treatment were able to attenuate cardiac arrhythmias caused by CIR; however, these antiarrhythmic effects were abolished by pretreatment with PROB and DPCPX. The total serum CK and CK-MB were similar in all groups. These results indicate that the pharmacological modulation of Ca2+/cAMP/ADO in cardiac cells by means of attenuation of Ca2+ influx via LTCC and the activation of A1R by endogenous ADO could be a promising therapeutic strategy to reduce the incidence of severe and fatal arrhythmias caused by AMI in humans.

15.
J Chem Phys ; 137(4): 044901, 2012 Jul 28.
Article in English | MEDLINE | ID: mdl-22852649

ABSTRACT

We numerically study a simple fluid composed of particles having a hard-core repulsion complemented by two patchy attractive sites on the particle poles. An appropriate choice of the patch angular width allows for the formation of ring structures which, at low temperatures and low densities, compete with the growth of linear aggregates. The simplicity of the model makes it possible to compare simulation results and theoretical predictions based on the Wertheim perturbation theory, specialized to the case in which ring formation is allowed. Such a comparison offers a unique framework for establishing the quality of the analytic predictions. We find that the Wertheim theory describes remarkably well the simulation results.

16.
J Chem Phys ; 137(8): 084704, 2012 Aug 28.
Article in English | MEDLINE | ID: mdl-22938256

ABSTRACT

We investigate the behavior of a patchy particle model close to a hard-wall via Monte Carlo simulation and density functional theory (DFT). Two DFT approaches, based on the homogeneous and inhomogeneous versions of Wertheim's first order perturbation theory for the association free energy are used. We evaluate, by simulation and theory, the equilibrium bulk phase diagram of the fluid and analyze the surface properties for two isochores, one of which is close to the liquid side of the gas-liquid coexistence curve. We find that the density profile near the wall crosses over from a typical high-temperature adsorption profile to a low-temperature desorption one, for the isochore close to coexistence. We relate this behavior to the properties of the bulk network liquid and find that the theoretical descriptions are reasonably accurate in this regime. At very low temperatures, however, an almost fully bonded network is formed, and the simulations reveal a second adsorption regime which is not captured by DFT. We trace this failure to the neglect of orientational correlations of the particles, which are found to exhibit surface induced orientational order in this regime.


Subject(s)
Colloids/chemistry , Monte Carlo Method , Quantum Theory , Particle Size , Surface Properties
17.
Int Braz J Urol ; 38(6): 750-9; discussion 759, 2012.
Article in English | MEDLINE | ID: mdl-23302413

ABSTRACT

PURPOSE: The study evaluates the clinical and pathological findings of 16 patients with locally advanced penile carcinoma (PC) submitted to emasculation, and discusses questions related to the usefulness of bilateral orchiectomy. MATERIALS AND METHODS: Between 1999 and 2010, 172 patients with PC were treated. Sixteen (9 %) underwent emasculation. Data were retrieved from the institution's database including age, ethnicity, date of surgery, residential setting, level of schooling, time to diagnosis, type of reconstruction, complications, tumor stage and grade, vascular and perineural invasion along with invasion of corpus cavernosum, corpus spongiosum, testicles, scrotum and urethra. RESULTS: A total of 16 patients (average: 63.1 years) with locally advanced PC were included. All were illiterate or semiliterate rural dwellers and 87% were white. The time to diagnosis was 8-12 months. The mean follow-up time was 31.9 months (1-119). By the time of the last follow-up, only seven patients (43.75%) were alive. Tumors were pT4 (n = 6), pT3 (n = 8), pT2 (n = 2), Grade I (n = 5) and Grade II (n = 11). The histopathological examination revealed invasion of the urethra (n = 13), scrotum (n = 5) and testicles (n = 1). The surgical margin was positive in one patient. Six patients (37.5%) had vascular invasion and 11 (68.7%) had perineural invasion. Currently, only one of the former is alive. CONCLUSIONS: The finding of focal microscopic testicular infiltration in only one of 32 testicles, even in the presence of clinically apparent scrotal invasion, suggests that emasculation without bilateral orchiectomy is a safe treatment option for patients with locally advanced PC.


Subject(s)
Carcinoma, Squamous Cell/surgery , Orchiectomy/methods , Penile Neoplasms/surgery , Testis/surgery , Adult , Aged , Carcinoma, Squamous Cell/pathology , Follow-Up Studies , Humans , Kaplan-Meier Estimate , Male , Middle Aged , Organ Sparing Treatments/methods , Penile Neoplasms/pathology , Prognosis , Time Factors , Treatment Outcome
18.
Clin Adv Periodontics ; 12(1): 32-38, 2022 03.
Article in English | MEDLINE | ID: mdl-33914411

ABSTRACT

INTRODUCTION: This paper presents a case report of immediate implant placement (IIP) with a provisionalization technique to restore function and esthetics with follow-up after 4 years. CASE PRESENTATION: Minimally traumatic extraction was performed with IIP, soft-tissue grafting, and immediate provisional crown. Six months after optimal healing, the patient was submitted to an esthetic restorative work through veneers in lithium disilicate. Fourteen-month and 4-year follow-up visits revealed stability of the peri-implant soft-tissues with peri-implant health status, with the evaluation of the pink and white esthetic score, yielding to mean scores, respectively, in 14 months of 11.62 ± 2.07 (pink esthetic score [PES]) and 18.25 ± 1.46 (PES/white esthetic score [WES]) and in 4 years of 11.0 ± 1.32 (PES) and 17.62 ± 0.65 (PES/WES). Intraoral digital radiographs showed minimal crestal bone level changes throughout the follow-up period. Thus, IIP is a sensitive technique procedure, and a 3D implant position is crucial for success. CONCLUSION: Immediate implant with grafting to fill the gap and soft tissue augmentation led to less horizontal changes and stable mucosal margin, and immediate provisionalization helped to maintain soft tissue architecture, and proper case selection is key for clinical success.


Subject(s)
Dental Implants, Single-Tooth , Dental Implants , Esthetics, Dental , Follow-Up Studies , Humans , Maxilla , Treatment Outcome
19.
Article in English | MEDLINE | ID: mdl-35329329

ABSTRACT

Amino acid complexes of zirconia represent an entirely new class of materials that were synthesized and studied for the first time for the decontamination of fluoride ion containing aqueous solutions. Glutamic and aspartic acid complexes of zirconia assembled with thin carbon (stacked graphene oxide) platelets deriving from graphite oxide (GO) were synthesized by a two-step method to prepare adsorbents. The characterization of the complexes was carried out using infrared spectroscopy to determine the functional groups and the types of interaction between the composites and fluoride ions. To reveal the mechanisms and extent of adsorption, two types of batch adsorption measurements were performed: (i) varying equilibrium fluoride ion concentrations to construct adsorption isotherms at pH = 7 in the absence of added electrolytes and (ii) using fixed initial fluoride ion concentrations (10 mg/L) with a variation of either the pH or the concentration of a series of salts that potentially interfere with adsorption. The experimental adsorption isotherms were fitted by three different theoretical isotherm equations, and they are described most appropriately by the two-site Langmuir model for both adsorbents. The adsorption capacities of Zr-glutamic acid-graphite oxide and Zr-aspartic acid-graphite oxide are 105.3 and 101.0 mg/g, respectively. We found that two distinct binding modes are combined in the Zr-amino acid complexes: at low solution concentrations, F- ions are preferentially adsorbed by coordinating to the surface Zr species up to a capacity of ca. 10 mg/g. At higher concentrations, however, large amounts of fluoride ions may undergo anion exchange processes and physisorption may occur on the positively charged ammonium moieties of the interfacially bound amino acid molecules. The high adsorption capacity and affinity of the studied dicarboxylate-type amino acids demonstrate that amino acid complexes of zirconia are highly variable materials for the safe and efficient capture of strong Lewis base-type ions such as fluoride.


Subject(s)
Graphite , Water Pollutants, Chemical , Water Purification , Adsorption , Amino Acids , Aspartic Acid , Carbon , Fluorides/chemistry , Graphite/chemistry , Hydrogen-Ion Concentration , Kinetics , Oxides , Water/chemistry , Water Pollutants, Chemical/analysis , Water Purification/methods , Zirconium/chemistry
20.
J Chem Phys ; 134(10): 104904, 2011 Mar 14.
Article in English | MEDLINE | ID: mdl-21405190

ABSTRACT

We investigate the effect of distinct bonding energies on the onset of criticality of low functionality fluid mixtures. We focus on mixtures of particles with two and three patches as this includes the mixture where "empty" fluids were originally reported. In addition to the number of patches, the species differ in the type of patches or bonding sites. For simplicity, we consider that the patches on each species are identical: one species has three patches of type A and the other has two patches of type B. We have found a rich phase behavior with closed miscibility gaps, liquid-liquid demixing, and negative azeotropes. Liquid-liquid demixing was found to pre-empt the "empty" fluid regime, of these mixtures, when the AB bonds are weaker than the AA or BB bonds. By contrast, mixtures in this class exhibit "empty" fluid behavior when the AB bonds are stronger than at least one of the other two. Mixtures with bonding energies ε(BB) = ε(AB) and ε(AA) < ε(BB), were found to exhibit an unusual negative azeotrope.

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