Fluorine in Complex Alumino-Boro-Silicate Glasses: Insight into Chemical Environment and Structure.

Fluorine incorporation into silicate glasses is important for technical fields as diverse as geophysics, extractive metallurgy, reconstructive dentistry, optical devices, and radioactive waste management. In this study, we explored the structural role of fluorine in alkaline alumino-borosilicate glass, with increasing amounts of fluorine up to 25 mol % F while maintaining the glass composition. Glasses were characterized by X-ray diffraction (XRD), 27Al and 19F magic angle spinning nuclear magnetic resonance (MAS NMR) spectroscopy, and electron probe microanalysis. Results showed that essentially all F was retained; however, between 12 and 15 mol % F (∼3.6 and 4.5 wt % F), excess fluorine partitions to CaF2 and then NaF and Na-Al-F crystalline phases. Even prior to crystallization, there exist five distinct F sites, three of which evolve into crystalline phases. The two persistent glassy sites likely involve [4]Al-F-Ca/Na local structures. We propose a general understanding of the expected chemical shift of 19F NMR in systems containing Al, Ca, and Na.

Composition-Structure-Solubility Relationships in Borosilicate Glasses: Toward a Rational Design of Bioactive Glasses with Controlled Dissolution Behavior.

Owing to their fast but tunable degradation kinetics (in comparison to silicates) and excellent bioactivity, the past decade has witnessed an upsurge in the research interest of borate/borosilicate-based bioactive glasses for their potential use in a wide range of soft tissue regeneration applications. Nevertheless, most of these glasses have been developed using trial-and-error approaches wherein SiO2 has been gradually replaced by B2O3. One major reason for using this empirical approach is the complexity of short-to-intermediate range structures of these glasses which greatly complicate the development of a thorough understanding of composition-structure-solubility relationships in these systems. Transitioning beyond the current style of composition design to a style that facilitates the development of bioactive glasses with controlled ion release tailored for specific patients/diseases requires a deeper understanding of the compositional/structural dependence of glass degradation behavior in vitro and in vivo. Accordingly, the present study aims to decipher the structural drivers controlling the dissolution kinetics and ion-release behavior of potentially bioactive glasses designed in the Na2O-B2O3-P2O5-SiO2 system across a broad compositional space in simulated body environments (pH = 7.4). By employing state-of-the-art spectroscopy-based characterization techniques, it has been shown that the degradation kinetics of borosilicate glasses depend on their R (Na2O/B2O3) and K (SiO2/B2O3) ratios, while the release of particular network-forming moieties from the glass into solution is strongly influenced by their role in-and effect on-the short-to-intermediate-range molecular structure. The current study aims to promote a rational design of borosilicate-based bioactive glasses, where a delicate balance between maximizing soft tissue regeneration and minimizing calcification and cytotoxicity can be achieved by tuning the release of ionic dissolution products (of controlled identity and abundance) from bioactive glasses into physiological media.

Dissolution kinetics of a sodium borosilicate glass in Tris buffer solutions: impact of Tris concentration and acid (HCl/HNO3) identity.

Understanding the corrosion behavior of glasses in near-neutral environments is crucial for many technologies including glasses for regenerative medicine and nuclear waste immobilization. To maintain consistent pH values throughout experiments in the pH = 7 to 9 regime, buffer solutions containing tris(hydroxymethyl)aminomethane ("Tris", or sometimes called THAM) are recommended in ISO standards 10993-14 and 23317 for evaluating biomaterial degradation and utilized throughout glass dissolution behavior literature-a key advantage being the absence of dissolved alkali/alkaline earth cations (i.e. Na+ or Ca2+) that can convolute experimental results due to solution feedback effects. Although Tris is effective at maintaining the solution pH, it has presented concerns due to the adverse artificial effects it produces while studying glass corrosion, especially in borosilicate glasses. Therefore, many open questions still remain on the topic of borosilicate glass interaction with Tris-based solutions. We have approached this topic by studying the dissolution behavior of a sodium borosilicate glass in a wide range of Tris-based solutions at 65 °C with varied acid identity (Tris-HCl vs. Tris-HNO3), buffer concentration (0.01 M to 0.5 M), and pH (7-9). The results have been discussed in reference to previous studies on this topic and the following conclusions have been made: (i) acid identity in Tris-based solutions does not exhibit a significant impact on the dissolution behavior of borosilicate glasses, (ii) ∼0.1 M Tris-based solutions are ideal for maintaining solution pH in the absence of obvious undesirable solution chemistry effects, and (iii) Tris-boron complexes can form in solution as a result of glass dissolution processes. The complex formation, however, exhibits a distinct temperature-dependence, and requires further study to uncover the precise mechanisms by which Tris-based solutions impact borosilicate glass dissolution behavior.

Machine learning as a tool to design glasses with controlled dissolution for healthcare applications.

The advancement of glass science has played a pivotal role in enhancing the quality and length of human life. However, with an ever-increasing demand for glasses in a variety of healthcare applications - especially with controlled degradation rates - it is becoming difficult to design new glass compositions using conventional approaches. For example, it is difficult, if not impossible, to design new gene-activation bioactive glasses, with controlled release of functional ions tailored for specific patient states, using trial-and-error based approaches. Notwithstanding, it is possible to design new glasses with controlled release of functional ions by using artificial intelligence-based methods, for example, supervised machine learning (ML). In this paper, we present an ensemble ML model for reliable prediction of time- and composition-dependent dissolution behavior of a wide variety of oxide glasses relevant for various biomedical applications. A comprehensive database, comprising of over 1300 data-records consolidated from original glass dissolution experiments, has been used for training and subsequent testing of prediction performance of the ML model. Results demonstrate that the ensemble ML model can predict chemical degradation behavior of glasses in aqueous solutions over a wide range of pH relevant for their usage in a human body where the environment can be highly acidic (for example, pH = 3), for example, due to secretion of citric acid by osteoclasts, or highly alkaline (pH ≈10) due to the release of alkali cations from bioactive glasses. Outcomes of this study can be leveraged to design glasses with controlled dissolution behavior in various biological environments. STATEMENT OF SIGNIFICANCE: In this paper, we present an ensemble machine learning (ML) model for prediction of dissolution behavior of a wide variety of oxide glasses relevant for various biomedical applications. The results demonstrate that the ML model can predict the chemical degradation behavior of glasses in aqueous solutions over a wide range of pH relevant for their usage in a human body where the environment can be highly acidic (for example, pH = 3), for example, due to secretion of citric acid by osteoclasts, or highly alkaline (pH ≈10) due to the release of alkali cations from bioactive glasses. Outcomes of this study can be leveraged to design new biomedical glasses with controlled (desired) dissolution behavior in various biological environments.

An insight into the corrosion of alkali aluminoborosilicate glasses in acidic environments.

The majority of the literature on glass corrosion focuses on understanding the dissolution kinetics and mechanisms of silicate glass chemistries in the neutral-to-alkaline aqueous regime owing to its relevance in the fields of nuclear waste immobilization and biomaterials. However, understanding the corrosion of silicate-based glass chemistries over a broad composition space in the acidic pH regime is essential for glass packaging and touch screen electronic display industries. A thorough literature review on this topic reveals only a handful of studies that discuss acid corrosion of silicate glasses and their derivatives-these include only a narrow set of silicate-based glass chemistries. Although the current literature successfully explains the dissolution kinetics of glasses based upon classically understood aqueous corrosion mechanisms, more recent advancements in atomic-scale characterization techniques, have enabled a better understanding of reactions taking place directly at the pristine glass-fluid interface which has facilitated the development of a unifying model describing corrosion behavior of silicate glasses. Based on the corrosion mechanisms described and the questions raised in preceding literature, the present study focuses on understanding the corrosion mechanisms governing metaluminous (Na/Al = 1) sodium aluminoborosilicate glasses in acidic environments across a wide composition-space (ranging from SiO2-rich to B2O3-rich compositions), with particular emphasis on understanding the reactions taking place near the glass-fluid interface. Using state-of-the-art characterization techniques including nuclear magnetic resonance (NMR) spectroscopy, Rutherford backscattering, X-ray photoelectron spectroscopy (XPS) and elastic recoil detection analysis (ERDA), it has been shown that stepwise B2O3 substitutions into nepheline (NaAlSiO4) glass, although causing non-linear changes in glass structure network structural features, leads to strikingly linear increases in the forward dissolution rate at pH = 2. While the glasses undergo congruent dissolution in the forward rate regime, the residual rate regime displays evidence of preferential extraction near the glass surface (i.e., enrichment in aluminum content upon corrosion through AlO4→ Al(OH)3 evolution) implying that dissolution-re-precipitation processes may occur at the glass-fluid interface in both B2O3-rich and SiO2-rich glass compositions-albeit with vastly dissimilar reaction kinetics.

Does Experience Matter? Paramedic Cardiac Resuscitation Experience Effect on Out-of-Hospital Cardiac Arrest Outcomes.

OBJECTIVE: Outcomes of Out-of-Hospital Cardiac Arrest (OHCA) are influenced by many factors. We postulate that paramedics who have participated in a greater number of OHCA resuscitations will have improved patient outcomes when compared to paramedics who participated in fewer resuscitations. METHODS: We conducted a retrospective analysis of prospectively collected data abstracted from the cardiac arrest database of a large urban EMS system. All OHCA cases where resuscitation was attempted during the year 2014 were reviewed. Our outcome of interest was the rate of sustained Return of Spontaneous Circulation (ROSC), which is defined as ROSC for five continuous minutes or greater. The rate of sustained ROSC was calculated from cases when paramedics served in the role of the lead medic. These rates were then analyzed using the Chi-Square test. RESULTS: A total of 1,145 cases of OHCA met criteria for inclusion in this study, of which 343 paramedics participated in at least one cardiac arrest in 2014. The median number of resuscitations was 10 with a range from 1 to 26 resuscitations. The paramedics were dichotomized into two groups; those who participated in <10 OHCAs (120/343), labeled "less experienced," and those who participated in ≥10 OHCAs (223/343), labeled "more experienced." Paramedics in the less experienced group had a sustained ROSC rate of 22.2% for resuscitations in which they were the lead medic, while those in the more experienced group had a rate of 28.9% (p-value = 0.047), RR 1.30 (95% CI 1.001, 1.692). CONCLUSIONS: This study demonstrated that more experienced paramedics had a statistically significant increase in achieving sustained ROSC when they were functioning in a lead role compared to less experienced paramedics. We found no other clinically significant patient outcomes related to the provider's experience.

Understanding the structural drivers governing glass-water interactions in borosilicate based model bioactive glasses.

The past decade has witnessed a significant upsurge in the development of borate and borosilicate based resorbable bioactive glasses owing to their faster degradation rate in comparison to their silicate counterparts. However, due to our lack of understanding about the fundamental science governing the aqueous corrosion of these glasses, most of the borate/borosilicate based bioactive glasses reported in the literature have been designed by "trial-and-error" approach. With an ever-increasing demand for their application in treating a broad spectrum of non-skeletal health problems, it is becoming increasingly difficult to design advanced glass formulations using the same conventional approach. Therefore, a paradigm shift from the "trial-and-error" approach to "materials-by-design" approach is required to develop new-generations of bioactive glasses with controlled release of functional ions tailored for specific patients and disease states, whereby material functions and properties can be predicted from first principles. Realizing this goal, however, requires a thorough understanding of the complex sequence of reactions that control the dissolution kinetics of bioactive glasses and the structural drivers that govern them. While there is a considerable amount of literature published on chemical dissolution behavior and apatite-forming ability of potentially bioactive glasses, the majority of this literature has been produced on silicate glass chemistries using different experimental and measurement protocols. It follows that inter-comparison of different datasets reveals inconsistencies between experimental groups. There are also some major experimental challenges or choices that need to be carefully navigated to unearth the mechanisms governing the chemical degradation behavior and kinetics of boron-containing bioactive glasses, and to accurately determine the composition-structure-property relationships. In order to address these challenges, a simplified borosilicate based model melt-quenched bioactive glass system has been studied to depict the impact of thermal history on its molecular structure and dissolution behavior in water. It has been shown that the methodology of quenching of the glass melt impacts the dissolution rate of the studied glasses by 1.5×-3× depending on the changes induced in their molecular structure due to variation in thermal history. Further, a recommendation has been made to study dissolution behavior of bioactive glasses using surface area of the sample - to - volume of solution (SA/V) approach instead of the currently followed mass of sample - to - volume of solution approach. The structural and chemical dissolution data obtained from bioactive glasses following the approach presented in this paper can be used to develop the structural descriptors and potential energy functions over a broad range of bioactive glass compositions. STATEMENT OF SIGNIFICANCE: Realizing the goal of designing third generation bioactive glasses requires a thorough understanding of the complex sequence of reactions that control their rate of degradation (in physiological fluids) and the structural drivers that control them. In this article, we have highlighted some major experimental challenges and choices that need to be carefully navigated in order to unearth the mechanisms governing the chemical dissolution behavior of borosilicate based bioactive glasses. The proposed experimental approach allows us to gain a new level of conceptual understanding about the composition-structure-property relationships in these glass systems, which can be applied to attain a significant leap in designing borosilicate based bioactive glasses with controlled dissolution rates tailored for specific patient and disease states.

Morel-LAvallee lesion initially diagnosed as quadriceps contusion: ultrasound, MRI, and importance of early intervention.

Morel-Lavallee lesions (MLL) are rare, closed degloving injuries caused by trauma that delivers a shearing force to the soft tissue most commonly of the hip. If not treated in the acute and subacute setting these lesions are often complicated by re-accumulation of fluid, infection, or chronic pain. We present a unique case of a recurrent, massive medial knee/thigh MLL in which proper treatment was delayed due to initial diagnosis of a quadriceps contusion. We describe the ultrasound and magnetic resonance imaging findings of this patient and based on a review of recent literature propose that the initial management should have included early drainage/debridement, which likely could have prevented recurrence and significantly shortened the clinical course.

Prevalence and clinical correlates of explosive outbursts in Tourette syndrome.

The aim of this study was to examine the prevalence and clinical correlates of explosive outbursts in two large samples of individuals with Tourette syndrome (TS), including one collected primarily from non-clinical sources. Participants included 218 TS-affected individuals who were part of a genetic study (N=104 from Costa Rica (CR) and N=114 from the US). The relationships between explosive outbursts and comorbid attention deficit hyperactivity disorder (ADHD), obsessive-compulsive disorder (OCD), tic severity, and prenatal and perinatal complications were examined using regression analyses. Twenty percent of participants had explosive outbursts, with no significant differences in prevalence between the CR (non-clinical) and the US (primarily clinical) samples. In the overall sample, ADHD, greater tic severity, and lower age of tic onset were strongly associated with explosive outbursts. ADHD, prenatal exposure to tobacco, and male gender were significantly associated with explosive outbursts in the US sample. Lower age of onset and greater severity of tics were significantly associated with explosive outbursts in the CR sample. This study confirms previous studies that suggest that clinically significant explosive outbursts are common in TS and associated with ADHD and tic severity. An additional potential risk factor, prenatal exposure to tobacco, was also identified.

Characteristics and comorbidity of ADHD sib pairs in the Central Valley of Costa Rica.

BACKGROUND: While genetic epidemiological studies demonstrate a substantial degree of genetic predisposition for attention-deficit/hyperactivity disorder (ADHD), they also suggest that the genetics are complex and may differ between populations or ethnic groups. OBJECTIVE: This study describes the phenomenology of siblings with ADHD from the genetically isolated population of the Central Valley of Costa Rica. METHODS: Rates of Diagnostic and Statistical Manual of Mental Disorders, Fourth Edition (DSM-IV)-defined ADHD subtypes and comorbid conditions were calculated in a sample of 157 ADHD-affected children (probands and siblings) recruited for genetic studies using standardized approaches. Sib-sib comparisons and logistic regressions were conducted to identify significant patterns of concordance. RESULTS: Combined-type ADHD (69.5%) was the most common subtype among probands, followed by the inattentive (27.4%), and hyperactive-impulsive (3.2%) subtypes. Anxiety disorders were prevalent (55.9%), as were disruptive behavior disorders (30.9%) and Tourette disorder (17.0%). Probands and siblings showed high sib-sib concordance for anxiety disorders. CONCLUSIONS: ADHD in Costa Rica is similar in clinical and demographic characteristics to ADHD seen in other parts of the world, although the rates of co-occurring psychiatric disorders differ somewhat from those previously reported in Latin American samples. Comorbid anxiety is prevalent, with high rates of sib-sib concordance, and may represent a distinct, homogeneous subgroup suitable for genetic studies.

Generation of hematopoietic humanized mice in the newborn BALB/c-Rag2null Il2rγnull mouse model: a multivariable optimization approach.

Hematopoietic humanized mice generated via transplantation of human hematopoietic stem cells (hHSCs) into immunodeficient mice are a valuable tool for studying development and function of the human immune system. This study was performed to generate a protocol that improves development and quality of humanized mice in the BALB/c-Rag2(null)Il2rγ(null) strain, testing route of injection, in vitro culture and freezing of hHSCs, types of cytokines in the culture, and co-injection of lineage-depleted CD34(-) cells. Specific hHSC culturing conditions and the addition of support cells were found to increase the frequency, and human hematopoietic chimerism, of humanized mice. The optimized protocol resulted in BALB/c-Rag2(null)Il2rγ(null) humanized mice displaying more consistent human hematopoietic and lymphoid engraftment. Thus, hematopoietic humanized mice generated on a BALB/c immunodeficient background represent a useful model to study the human immune system.

[Prevalence of and screening for ADHD in Costa Rica]. / Prevalencia y tamizaje del Trastorno por Déficit de Atención con Hiperactividad en Costa Rica.

This research project sought to estimate the prevalence of Attention-Deficit/Hyperactivity Disorder (ADHD) and to determine if the Swanson Nolan and Pelham Rating Scale IV (SNAP-IV) Spanish version is a useful screening tool in a population of Costa Rican school children. The SNAP-IV Spanish version was given to the parents and teachers of 425 children aged 5 to 13 (mean 8.8). All subjects were also assessed with the Swanson, Kotkin, Agler, M-Flynn and Pelham Scale (SKAMP), along with diagnostic confirmation by clinical interview. The sensitivity and specificity of the SNAP-IV was assessed as a predictor of DSM-IV ADHD diagnosis. The point prevalence of Attention Deficit Hyperactivity Disorder (ADHD) in this sample was 5%. The prevalence of ADHD among girls was 7%, while that among boys was 4%. The optimal screen was the teacher-rated SNAP-IV at a 20% cutoff, which had a sensitivity of 96% and specificity of 82%. Parent sensitivities were lower than teacher sensitivities. SNAP-IV teacher ratings with a cutoff isolating the top 20% of scores correctly categorized 87% of children.

Total knee arthroplasty in post-traumatic arthrosis of the knee.

Total knee arthroplasty is an effective method of treatment for the majority of patients with a prior distal femoral or tibial plateau fracture and end-stage arthritis. There is a higher complication rate and overall poorer outcome when compared with routine primary total knee arthroplasty. In patients for whom the goals of optimal limb and implant alignment are achieved, the results are comparable with routine primary knee arthroplasty. Patients with suboptimal component positioning or residual deformity have a poorer outcome. The technical challenges encountered can require skills, implant systems, and methods usually reserved for complex revision arthroplasty.

Total knee arthroplasty in patients with a prior fracture of the tibial plateau.

BACKGROUND: A fracture of the tibial plateau may predispose the knee to the development of posttraumatic arthritis. Malunion, intra-articular chondro-osseous defects, limb malalignment, retained internal fixation devices, and poor surrounding soft tissues may in turn compromise the outcome of total knee arthroplasty. The aim of our study was to evaluate the results of total knee arthroplasty in patients with a previous fracture of the tibial plateau. METHODS: The results of sixty-two condylar total knee arthroplasties performed with cement, from 1988 to 1999, in sixty-two patients with a previous fracture of the tibial plateau were reviewed. The fracture of the tibial plateau had been treated by open reduction and internal fixation in thirty-eight knees, external fixation in one knee, and nonoperatively in twenty-three knees. There were forty women and twenty-two men with an average age of sixty-three years at the time of the arthroplasty. Knee Society scores were recorded preoperatively and at the time of follow-up, at an average of 4.7 years, and complications were noted. No patient was lost to follow-up. RESULTS: The mean Knee Society scores improved significantly (p < 0.0001), from 43.9 points for pain and 52 points for function preoperatively to 82.9 and 84 points, respectively, at the time of the latest follow-up. There were thirteen reoperations, which included manipulation with the patient under anesthesia (five knees), wound revision (three knees), and component revision (five knees). There were six intraoperative complications (10%). A postoperative complication occurred in sixteen knees (26%). CONCLUSIONS: The vast majority of patients treated with total knee arthroplasty after a previous fracture of the tibial plateau have substantial improvement in function and relief of pain. However, these patients are at increased risk for perioperative complications, as evidenced by the high reoperation rate of 21% in this study.