Exploiting Organometallic Chemistry to Functionalize Small Cuprous Oxide Colloidal Nanocrystals.

The ligand chemistry of colloidal semiconductor nanocrystals mediates their solubility, band gap, and surface facets. Here, selective organometallic chemistry is used to prepare small, colloidal cuprous oxide nanocrystals and to control their surface chemistry by decorating them with metal complexes. The strategy is demonstrated using small (3-6 nm) cuprous oxide (Cu2O) colloidal nanocrystals (NC), soluble in organic solvents. Organometallic complexes are coordinated by reacting the surface Cu-OH bonds with organometallic reagents, M(C6F5)2, M = Zn(II) and Co(II), at room temperature. These reactions do not disrupt the Cu2O crystallinity or nanoparticle size; rather, they allow for the selective coordination of a specific metal complex at the surface. Subsequently, the surface-coordinated organometallic complex is reacted with three different carboxylic acids to deliver Cu-O-Zn(O2CR') complexes. Selective nanocrystal surface functionalization is established using spectroscopy (IR, 19F NMR), thermal gravimetric analyses (TGA), transmission electron microscopy (TEM, EELS), and X-ray photoelectron spectroscopy (XPS). Photoluminescence efficiency increases dramatically upon organometallic surface functionalization relative to that of the parent Cu2O NC, with the effect being most pronounced for Zn(II) decoration. The nanocrystal surfaces are selectively functionalized by both organic ligands and well-defined organometallic complexes; this synthetic strategy may be applicable to many other metal oxides, hydroxides, and semiconductors. In the future, it should allow NC properties to be designed for applications including catalysis, sensing, electronics, and quantum technologies.

Effect of Encapsulated Beet Extracts (Beta vulgaris) Added to Yogurt on the Physicochemical Characteristics and Antioxidant Activity.

Beet has been used as an ingredient for functional foods due to its high antioxidant activity, thanks to the betalains it contains. The effects of the addition of beet extract (liquid and lyophilized) on the physicochemical characteristics, color, antioxidant activity (AA), total betalains (TB), total polyphenols (TP), and total protein concentration (TPC) were evaluated on stirred yogurt. The treatments (T1-yogurt natural, T2-yogurt added with beet juice, T3-added extract of beet encapsulated with maltodextrin, and T4-yogurt added with extract of beet encapsulated with inulin) exhibited results with significant differences (p < 0.05). The highest TB content was observed in T2 (209.49 ± 14.91), followed by T3 (18.65 ± 1.01) and later T4 (12.96 ± 0.55). The highest AA was observed on T2 after 14 days (ABTS˙ 0.819 mM TE/100 g and DPPH˙ 0.343 mM TE/100 g), and the lowest was found on T1 at day 14 (ABTS˙ 0.526 mM TE/100 g and DPPH˙ 0.094 mM TE/100 g). A high content of TP was observed (7.13 to 9.79 mg GAE/g). The TPC varied between 11.38 to 12.56 µg/mL. The addition of beet extract significantly increased AA in yogurt, betalains being the main compounds responsible for that bioactivity.

Characterization of Beet Root Extract (Beta vulgaris) Encapsulated with Maltodextrin and Inulin.

Betalains are powerful antioxidants contained in beets. These are divided into betacyanins (red-violet) and betaxanthins (yellow-orange), and they can be used as natural colorants in the food industry. The effects of freeze-drying pure beet juice (B) and the encapsulation of beet juice with a dextrose equivalent (DE) 10 maltodextrin (M) and agave inulin (I) as carrier agents were evaluated. The powders showed significant differences (p < 0.05) in all the variables analyzed: water absorption index (WAI), water solubility index (WSI), glass transition temperature (Tg), total betalains (TB), betacyanins (BC), betaxanthins (BX), total polyphenols (TP), antioxidant activity (AA, via 2,2'-azino-bis(3-ethylbenzothiazoline-6-sulfonic acid)) (ABTS), and 2,2-diphenyl-1-picrylhydrazyl (DPPH)) and total protein concentration (TPC). The highest values of antioxidant activity were found in the non-encapsulated beet powder, followed by the powder encapsulated with maltodextrin and, to a lesser extent, the powder encapsulated with inulin. The glass transition temperature was 61.63 °C for M and 27.59 °C for I. However, for B it was less than 18.34 °C, which makes handling difficult. Encapsulation of beet extract with maltodextrin and inulin by lyophilization turned out to be an efficient method to increase solubility and diminish hygroscopicity.

Effect of extrusion cooking on bioactive compounds in encapsulated red cactus pear powder.

Red cactus pear has significant antioxidant activity and potential as a colorant in food, due to the presence of betalains. However, the betalains are highly thermolabile, and their application in thermal process, as extrusion cooking, should be evaluated. The aim of this study was to evaluate the effect of extrusion conditions on the chemical components of red cactus pear encapsulated powder. Cornstarch and encapsulated powder (2.5% w/w) were mixed and processed by extrusion at different barrel temperatures (80, 100, 120, 140 °C) and screw speeds (225, 275, 325 rpm) using a twin-screw extruder. Mean residence time (trm), color (L*, a*, b*), antioxidant activity, total polyphenol, betacyanin, and betaxanthin contents were determined on extrudates, and pigment degradation reaction rate constants (k) and activation energies (Ea) were calculated. Increases in barrel temperature and screw speed decreased the trm, and this was associated with better retentions of antioxidant activity, total polyphenol, betalain contents. The betacyanins k values ranged the -0.0188 to -0.0206/s and for betaxanthins ranged of -0.0122 to -0.0167/s, while Ea values were 1.5888 to 6.1815 kJ/mol, respectively. The bioactive compounds retention suggests that encapsulated powder can be used as pigments and to provide antioxidant properties to extruded products.

Effect of different calcium sources on the bioactive compounds stability of extruded and nixtamalized blue maize flours.

The stability of antioxidants in extruded and nixtamalized blue maize flours with calcium hydroxide [Ca(OH)2] and calcium lactate [C6H10O6Ca] were evaluated. Extruded blue maize flours batches were obtained by mixing blue maize flours separately with different Ca(OH)2 (0.1, 0.2 and 0.3 %) and C6H10O6Ca (0.3, 0.6 and 0.9 %) concentrations respectively and extruded to obtain the extruded flours. For nixtamalized flours, the maize grains were cooked at 1 % Ca(OH)2 and 2.95 % C6H10O6Ca concentrations respectively. Color, antioxidant activity, total phenolics, total anthocyanins and individual anthocyanins, contents were analyzed. Color, antioxidant activity, anthocyanins contents and total phenolics decreased as the calcium hydroxide concentration increased. In contrast, increasing the calcium lactate concentration on the extruded flours had the opposite effect. The extrusion process retained 57-47 %, 72-62 % and 79-65 % of the anthocyanins content, total phenolic content and antioxidant activity, respectively. These retention rates were higher than those of the nixtamalized flours using the same calcium sources. Cyanidin-3-glucoside and pelargonidin-3-glucoside were identified in the maize kernel and flours. Cyanidin-3-glucoside concentration was increased by both extrusion and nixtamalization processed with either of the two calcium sources. In contrast, pelargonidin-3-glucoside concentration decreased by both processes. Other anthocyanins were observed, but they were not identified.

Distribution of fractured bones among children: Experience with the Comprehensive Pediatric AO classification in a children's orthopedic hospital in Bogotá-Colombia.

INTRODUCTION: Fractures in children and adolescents are a public health issue. However, reliable epidemiological descriptions of the South American population must be improved. This study aims to present epidemiological data on fractures from a children's orthopedic hospital in one of the five largest cities in Latin America. PATIENTS AND METHODS: Descriptive epidemiological data from 2015 to 2019 were used to characterize children's fractures. Demographic variables, the number of fractured bones, high-energy trauma findings, fracture characteristics, fingertip injuries, and associated complications discriminated by the type of treatment are presented. Long bone fractures were classified according to the AO classification. All children less than 18 years of age were included. RESULTS: In a population of 3,616 children, 4,596 fractures were identified. More boys than girls sustain a fractured bone, with ratios as high as 6:1 around 15 years old. Distal forearm fractures were the most common (31.9%), followed by distal humerus (20.2%). Most of the complications were related to these two sites of fractures. The OR of complications between surgical and conservative management was 2.86. CONCLUSION: Epidemiological data of fractures from the authors' institution display the usual trending reported in most populations. Gender-related and age-related differences were relevant. Most fractures and complications are related to upper limb low-energy trauma. The most frequent are loss of ROM and loss of reduction. LEVEL OF EVIDENCE: Level III - retrospective cohort study.

FPGA-based real-time simulation of mismatched photovoltaic arrays.

This paper proposes an approach to the real time simulation of photovoltaic (PV) arrays that are subjected to mismatching conditions, e.g. partial shadowing. The method, which has been named Model by Zone (MbZ), adopts the best PV model depending on the operating conditions of the cells in the module: it switches among single-diode model (SDM), linear model and constant voltage model. An optimized digital hardware architecture exploiting parallelism of operations over a FPGA system is exploited to effectively implement the proposed model. It reduces the computation time and the use of hardware resources. The good trade-off between accuracy and computation time of the proposed technique has been demonstrated in two cases of study: by evaluating the long-term PV power production of a PV field subjected to dynamic shadowing conditions and by analyzing the model performance in a maximum power point tracking (MPPT) application. In the former case, the proposed approach improves the computation time by 182.5 % with respect to methods that are available in recent literature, with a Relative Error (RE) at the Global Maximum Power Point (GMPP) lower than 0.39 % . In the MPPT application, the proposed technique allows to achieve a MAPE of 0.0319 % and 0.1892 % in the string voltage and power calculation, respectively.

Pulmonary cement embolism following transpedicular screws placement for thoracolumbar fractures.

BACKGROUND: Symptomatic pulmonary cement embolism in patients undergoing thoracic transpedicular fenestrated screw placement is rare. Here, we have added a 64-year-old female undergoing transpedicular screw placement for a T11 fracture who developed a pulmonary cement embolism intraoperatively and add this case to 13 others identified in the literature. CASE DESCRIPTION: A 64-year-old female presented with a type "C", ASIA "E" T11 fracture. The thoracolumbar pedicle screw fixation was supplemented with bone cement due to her underlying severe osteoporosis. During the fluoroscopy-guided supplementation with bone cement, a leak through the paravertebral venous system was noted. Thirty minutes later, the patient acutely developed extreme respiratory failure and required mechanical ventilation for the next 2 days. The diagnosis of pulmonary embolism due to bone cement was confirmed on a contrast computed tomography study of the chest. CONCLUSION: Symptomatic pulmonary cement embolization supplementing transpedicular screws placement for osteoporotic bone is rare. Here, we present a 64-year-old female who during transpedicular fixation of a T11 fracture developed an acute pulmonary embolism from the bone cement resulting in the need for 2 days of postoperative artificial ventilation.

CuInS2 Quantum Dot and Polydimethylsiloxane Nanocomposites for All-Optical Ultrasound and Photoacoustic Imaging.

Dual-modality imaging employing complementary modalities, such as all-optical ultrasound and photoacoustic imaging, is emerging as a well-suited technique for guiding minimally invasive surgical procedures. Quantum dots are a promising material for use in these dual-modality imaging devices as they can provide wavelength-selective optical absorption. The first quantum dot nanocomposite engineered for co-registered laser-generated ultrasound and photoacoustic imaging is presented. The nanocomposites developed, comprising CuInS2 quantum dots and medical-grade polydimethylsiloxane (CIS-PDMS), are applied onto the distal ends of miniature optical fibers. The films exhibit wavelength-selective optical properties, with high optical absorption (> 90%) at 532 nm for ultrasound generation, and low optical absorption (< 5%) at near-infrared wavelengths greater than 700 nm. Under pulsed laser irradiation, the CIS-PDMS films generate ultrasound with pressures exceeding 3.5 MPa, with a corresponding bandwidth of 18 MHz. An ultrasound transducer is fabricated by pairing the coated optical fiber with a Fabry-Pérot (FP) fiber optic sensor. The wavelength-selective nature of the film is exploited to enable co-registered all-optical ultrasound and photoacoustic imaging of an ink-filled tube phantom. This work demonstrates the potential for quantum dots as wavelength-selective absorbers for all-optical ultrasound generation.

Optimisation of the ultrasound-assisted extraction of betalains and polyphenols from Amaranthus hypochondriacus var. Nutrisol.

The present study optimised the ultrasound-assisted extraction (UAE) of bioactive compounds from Amaranthus hypochondriacus var. Nutrisol. Influence of temperature (25.86-54.14 °C) and ultrasonic power densities (UPD) (76.01-273.99 mW/mL) on total betalains (BT), betacyanins (BC), betaxanthins (BX), total polyphenols (TP), antioxidant activity (AA), colour parameters (L*, a*, and b*), amaranthine (A), and isoamaranthine (IA) were evaluated using response surface methodology. Moreover, betalain extraction kinetics and mass transfer coefficients (KLa) were determined for each experimental condition. BT, BC, BX, TP, AA, b*, KLa, and A were significantly affected (p < 0.05) by temperature extraction and UPD, whereas L*, a*, and IA were only affected (p < 0.05) by temperature. All response models were significantly validated with regression coefficients (R2) ranging from 87.46 to 99.29%. BT, A, IA, and KLa in UAE were 1.38, 1.65, 1.50, and 29.93 times higher than determined using conventional extraction, respectively. Optimal UAE conditions were obtained at 41.80 °C and 188.84 mW/mL using the desired function methodology. Under these conditions, the experimental values for BC, BX, BT, TP, AA, L*, a*, b*, KLa, A, and IA were closely related to the predicted values, indicating the suitability of the developed quadratic models. This study proposes a simple and efficient UAE method to obtain betalains and polyphenols with high antioxidant activity, which can be used in several applications within the food industry.

Severe asthma: adding new evidence - Latin American Thoracic Society.

This document constitutes a summary of the clinical practice guidelines (CPGs) prepared at the initiative of the Latin American Thoracic Society (ALAT). Due to new evidence in the treatment of severe asthma, it was agreed to select six clinical questions, and the corresponding recommendations are provided herein. After considering the quality of the evidence, the balance between desirable and undesirable impacts and the feasibility and acceptance of procedures, the following recommendations were established. 1) We do not recommend the use of an inhaled corticosteroid (ICS) plus formoterol as rescue medication in the treatment of severe asthma. 2) We suggest performing many more high-quality randomised studies to evaluate the efficacy and safety of tiotropium in patients with severe asthma. 3) Omalizumab is recommended in patients with severe uncontrolled allergic asthma with serum IgE levels above 30 IU. 4) Anti-interleukin (IL)-5 drugs are recommended in patients with severe uncontrolled eosinophilic asthma (cut-off values above 150 cells·µL-1 for mepolizumab and above 400 cells·µL-1 for reslizumab). 5) Benralizumab is recommended in adult patients with severe uncontrolled eosinophilic asthma (cut-off values above 300 cells·µL-1). 6) Dupilumab is recommended in adult patients with severe uncontrolled allergic and eosinophilic asthma and in adult patients with severe corticosteroid-dependent asthma.

[Out-of-hospital delivery. Experience of ten years in Jalisco, Mexico]. / Parto fortuito. Experiencia de diez años en Jalisco, México.

BACKGROUND: Birth without medical assistance, or outs hospitals is defined as one that occurs without the optimal medical and health care conditions for mother and son pairing. Frequency of this phenomenon is not known in Mexico. OBJECTIVE: To observe clinical outcomes, morbidity, mortality, epidemiological and geographical patterns. MATERIAL AND METHOD: A retrospective study including newborns of mothers who have had deliveries without medical assistance in accidental conditions, admitted to Unidad de Cuidados Intensivos Neonatales Externos, Hospital Civil de Guadalajara Fray Antonio Alcalde (Mexico). From January 2000 to December 2009. RESULTS: In 4,762 (100%) neonatal records evaluated, 582 (12%) were newborns birth for deliveries out of hospital. 314 (54%) female and 268 (46%) male, first mother's gravidity 195 (33%) and second o more gravidity 387 (68%) were registered. The Hospital stay average was 3-day. Discharge diagnoses: healthy 463 (79%), neonatal sepsis 16 (4%), respiratory distress 35 (6%), jaundice 33 (6%), pneumonia 12 (2%), metabolic disorders 13 (3%), other diagnoses 10 (2%). Place of births: 366 Guadalajara metropolitan area (63%), state of Jalisco, 180 (31%) other states of the Mexican Republic 36 (6%). Lambed at home 117 (20%), 52 bath home (9%), toilet bowl 29 (5%), car 128 (22%), road 58 (10%), hospital admission 104 (18%), Ambulance 42 (7%) Other 52 (9%). CONCLUSION: In our study we observed that 79% of the newborns were healthy. They are the third leading cause of admission to Neonatal Intensive Care Unit External. The most common neonatal complications were solved without consequence. No neonatal mortality cases were founded.

Understanding the mechanochemical synthesis of the perovskite LaMnO3 and its catalytic behaviour.

Mechanochemistry offers a solventless, 'waste free' route to preparing metal oxide catalysts, however, there is limited information on the chemical steps involved. In this work, the perovskite LaMnO3 has been successfully synthesized via mechanochemistry from metal oxide powders, La2O3 and Mn2O3, at room temperature, using a planetary ball mill. Separate ex situ'time slices' were taken during the milling procedure to provide insights into the underlying chemistry. The crystalline material was assessed using XRD, which identified 100% perovskite phase after 3 h of milling. Conversely, characterization by X-ray absorption spectroscopy (XAS) at both the Mn K-edge and La L3-edge provides a very different picture. The XAS data shows that there are significant structural alterations as early as 30 min of milling, with the La precursor dispersed over Mn2O3. Increasing milling time then allows for mechanical activation of both precursors and the formation of powdered LaMnO3, with no calcination step required. The XAS highlights that there is a significant amount of amorphous, oxygen deficient, content even when XRD has identified 100% perovskite phase. The samples were tested for the decomposition of the environmental pollutant N2O; at a milling time of 3 h, the LaMnO3 catalyst displays a much early onset production of N2 compared to a traditional sol-gel synthesized LaMnO3, resulting from increased oxygen deficiency at the surface, confirmed by XPS and STEM-EELS. This is an encouraging sign that mechanochemical routes can be harnessed to provide a sustainable route to preparing mixed metal oxide catalysts with enhanced catalytic performance.

A new method for the inoculation of Phytophthora palmivora (Butler) into cacao seedlings under greenhouse conditions.

BACKGROUND: The black pod disease affects cacao plantations worldwide; it is caused by the oomycete species of the genus Phytophthora. The resistance of cacao plants to the black pod is commonly evaluated by artificial inoculation of the pathogen and the monitoring of the disease symptoms. However, it is difficult to identify resistant plants because the commonly used methods for the inoculation of the pathogens produce inconsistent results. Therefore, this study aimed to develop an efficient and reliable method to evaluate the resistance of Theobroma cacao seedlings to the infection by Phytophthora palmivora. RESULTS: Seedlings of different cacao genotypes were inoculated with P. palmivora under greenhouse conditions using the previously reported inoculation methods and a newly proposed method, the agar-water solution method. While none of the previously reported methods was effective, the agar-water solution method ensured a 100% seedling infection under greenhouse conditions. The proposed agar-water methodology is fast, simple and reproducible. Furthermore, the evaluation of this method in susceptible (CCN-51) and tolerant (SCA-6) T. cacao genotypes produced the expected contrasting results. CONCLUSIONS: The agar-water solution method presented in this study is an efficient alternative inoculation protocol for the identification of cacao genotypes that are resistant to black pod under greenhouse conditions.

Long-time saturation of the Loschmidt echo in quantum chaotic billiards.

The Loschmidt echo (LE) (or fidelity) quantifies the sensitivity of the time evolution of a quantum system with respect to a perturbation of the Hamiltonian. In a typical chaotic system the LE has been previously argued to exhibit a long-time saturation at a value inversely proportional to the effective size of the Hilbert space of the system. However, until now no quantitative results have been known and, in particular, no explicit expression for the proportionality constant has been proposed. In this paper we perform a quantitative analysis of the phenomenon of the LE saturation and provide the analytical expression for its long-time saturation value for a semiclassical particle in a two-dimensional chaotic billiard. We further perform extensive (fully quantum mechanical) numerical calculations of the LE saturation value and find the numerical results to support the semiclassical theory.

Semiclassical theory for decay and fragmentation processes in chaotic quantum systems.

We consider quantum decay and photofragmentation processes in open chaotic systems in the semiclassical limit. We devise a semiclassical approach which allows us to consistently calculate quantum corrections to the classical decay to high order in an expansion in the inverse Heisenberg time. We present results for systems with and without time-reversal symmetry, as well as for the symplectic case, and extend recent results to nonlocalized initial states. We further analyze related photodissociation and photoionization phenomena and semiclassically compute cross-section correlations, including their Ehrenfest-time dependence.

[Non-suicidal self-injuries in adolescents: Prevention and detection in primary care]. / Autolesiones no suicidas en adolescentes: prevención y detección en la atención primaria.

Non-suicidal self-injuries (NSSI) are self-harm behaviours without a suicidal objective, and have a prevalence of 17-18% in adolescents. It is characterised by self-inflicted injuries, mainly in the extremities and abdomen. The psychopathology is subject to the presence of emotional deregulation, in which it seeks the masking of emotional pain with physical pain. A literature review was conducted using research in databases, including key words in English and Spanish. It was found that the identification of NSSI risk factors in adolescents helps in its prevention and identification, and as such it was proposed to classify the NSSI risk factors, as well as the tools for their identification in primary care. It was concluded that the management of NSSI corresponds to the child and adolescent psychiatrist, but primary care physicians have a fundamental role in its detection and prevention.

Descripción del crecimiento del fémur proximal mediante tomografía en pacientes pediátricos sin enfermedad de cadera / Description of proximal femoral growth in pediatric patients without hip disorders using tomography

Objetivo: Describir el crecimiento femoral proximal en una población latinoamericana a través del desplazamiento femoral, el ángulo cervico-diafisario, la longitud del cuello femoral y el diámetro de la cabeza femoral evaluados con tomografía computarizada en pacientes pediátricos sin enfermedad de cadera. Materiales y métodos: Estudio retrospectivo que evaluó imágenes de tomografía computarizada de caderas de pacientes sanos <18 años. Se tomaron las siguientes medidas: desplazamiento femoral, longitud del cuello femoral, diámetro de la cabeza femoral y ángulo cervico-diafisario. Resultados:El desplazamiento femoral aumenta 1,96 mm hasta los 12.5 años, y desde los 12.5 hasta los 16 años, aumenta 1,2 mm. Se constató un aumento lineal del crecimiento de la longitud del cuello femoral. El ángulo cervico-diafisario disminuyó progresivamente hasta los 12 años. A partir de ese momento, la curva se aplanó. Se observó un aumento anual del diámetro de la cabeza femoral de 1,56 mm hasta los 13 años y de 0,62 mm anuales, en adelante. Conclusiones: Las medidas descritas en este estudio son esenciales para el seguimiento, el diagnóstico o el abordaje conductual en múltiples cuadros articulares de cadera durante el crecimiento. Se expone la necesidad de realizar estudios más amplios para establecer rangos de normalidad en la población local con las herramientas tecnológicas disponibles, que fundamenten una referencia para la restauración de la anatomía en la cirugía de preservación.Palabras clave: Cabeza femoral; cuello femoral; desarrollo humano. Nivel de Evidencia :IV

Introduction: This study aims to perform a descriptive analysis of proximal femoral growth in a Latin-American population through femoral offset, neck-shaft angle, femoral neck length, and femoral head diameter evaluated through computed tomography in pediatric patients without hip pathology. Materials and methods: Retrospective study evaluating CT images of the hips of healthy patients under 18 years. The following measurements were taken by a trained orthopedist: femoral offset, femoral neck length, femoral head diameter, and neck-shaft angle. Results:Femoral offset increases by 1.96 mm until age 12.5. From 12.5 to 16 years of age, it increases by 1.2 mm. A constant rise in the growth of the femoral neck length was found. The neck-shaft angle presented a progressive decrease until age 12. After that point, the curve flattened. An increase in femoral head diameter of 1.56 mm per year was observed until age 13 and then 0.62 mm per year. Conclusions: The measurements evaluated in this study are essential for the diagnosis, follow-up, and treatment approach in hip pathologies during growth. More extensive research is needed to define normal ranges that will serve as a baseline for anatomy restoration in hip joint preservation surgery. Level of Evidence: IV

Extracting structural information of Au colloids at ultra-dilute concentrations: identification of growth during nanoparticle immobilization.

Sol-immobilization is increasingly used to achieve supported metal nanoparticles (NPs) with controllable size and shape; it affords a high degree of control of the metal particle size and yields a narrow particle size distribution. Using state-of-the-art beamlines, we demonstrate how X-ray absorption fine structure (XAFS) techniques are now able to provide accurate structural information on nano-sized colloidal Au solutions at µM concentrations. This study demonstrates: (i) the size of Au colloids can be accurately tuned by adjusting the temperature of reduction, (ii) Au concentration, from 50 µM to 1000 µM, has little influence on the average size of colloidal Au NPs in solution and (iii) the immobilization step is responsible for significant growth in Au particle size, which is further exacerbated at increased Au concentrations. The work presented demonstrates that an increased understanding of the primary steps in sol-immobilization allows improved optimization of materials for catalytic applications.

Suicide in University students in Bogotá, Colombia, 2004-2014. / Suicidio en estudiantes universitarios en Bogotá, Colombia, 2004­2014.

We report the results of a retrospective, descriptive, qualitative study of suicide among university students in Bogotá, Colombia. The objective of this study was to document the magnitude, principal characteristics, and impact of this phenomenon in the selected population. A semi-structured survey was employed to collect information from 66 individuals linked to the universities. A total of 45 cases of suicide were documented in the study period (2004 - 2014). Of these, 69% occurred in males and 31% in females. The age range was 17 - 27 years, with 62% of the cases in the 19 - 22 year-old group. The most common mechanisms employed were suffocation and poisoning, followed by intentional falls, use of a firearm, and drug overdose. The selected location was the place of residence in 52% of cases and the university campus in 16% of cases. The distribution of students by area of knowledge showed a predominance of social and human science (44%) followed by engineering (22%). A history of difficulties in family and affective relationships was common among victims, as was a history of exposure to intolerance of differences in sexual orientation. The individuals surveyed expressed a wide range of interpretations of the significance of suicide, both positive (courage, self-affirmation, autonomy) and negative (defeat, despair, and an inability to adapt).