Growth, coalescence and equilibration of metallic nanoparticles and nanoalloys studied by computational methods

Among nanoscale systems, metallic nanoparticles (NPs) certainly play a primary role, due to their highly tunable properties and to the wide variety of their applications. The properties of NPs are known to strongly depend on their size and geometric shape. In the case of bimetallic nanoparticles, also known as nanoalloys, further parameters can be exploited, i.e. the NP composition and the spatial arrangement of the two atomic species within the NP volume, here referred to as chemical ordering. Within this framework, the fine control of the NP configuration (here intended as the interplay between size, shape, composition and chemical ordering) is essential in sight of the possible technological applications. To this aim, a deep understanding of the NP formation process is highly desirable: one has to clearly know what are the different stages of such process, and what are the physical forces and the chemical effects involved. Moreover, a clear knowledge of the thermodynamic stability of the produced phases under the operating conditions is desirable as well. Computer simulations can be of great help in this sense, as they can provide clear information on both the equilibrium properties and the kinetic behaviour of the NPs. Specifically, the most thermodynamically favourable configurations of a given system can be determined, and the evolution pathways can be simulated and analysed at the atomic level, therefore allowing to rationalize the experimental findings. This Ph.D. thesis is devoted to the computational study of mono- and bi-metallic NPs, with particular attention to some of the nonequilibrium phenomena undergone by them. Different examples are presented and discussed; specifically, different metallic systems are treated, all of which are of great interest due to their practical applications, and different phenomena are analysed

PENINGKATAN KEMAMPUAN BERBICARA ANAK MELALUI PENGGUNAAN MEDIA GAMBAR BERSERI DI TAMAN KANAK-KANAK KARTIKA JAYA XX-40 PAREPARE

NELLI DIANA, 2014. Peningkatan Kemampuan Berbicara Anak Melalui Penggunaan Media Gambar Berseri Di Taman Kanak-Kanak Kartika Jaya XX-40 Parepare. Skripsi dibimbing oleh Dra. Hj. Sumartini, M.Pd dan Azizah Amal, S.S, M.Pd. Pendidikan Guru Pendidikan Anak Usia Dini Fakultas Ilmu Pendidikan Universitas Negeri Makassar. Rumusan masalah dalam penelitian ini adalah bagaimanakah penggunaan media gambar berseri dalam meningkatkan kemampuan berbicara anak di taman kanak-kanak Kartika Jaya XX-40 Parepare?, Tujuan penelitian untuk mengetahui bagaimana penggunaan media gambar berseri dalam meningkatkan kemampuan berbicara anak di taman kanak-kanak Kartika Jaya XX-40 Parepare. Penelitian ini menggunakan pendekatan penelitian kualitatif dengan jenis penelitian Tindakan Kelas. Lokasi penelitian ini di Taman Kanak-Kanak Kartika Jaya XX-40 Parepare. Subjek penelitian ini adalah kelompok B sebanyak 10 orang dan 1 orang guru. Pengumpulan data dengan teknik observasi dan dokumentasi. Sedangkan teknik analisis data yang digunakan adalah analisis kualitatif. Hasil penelitian menunjukkan bahwa melalui penggunaan media gambar berseri di Taman Kanak-Kanak Kartika Jaya XX-40 Parepare dapat meningkatkan kemampuan berbicara anak. Pada siklus I masih terdapat kekurangan-kekurangan, dimana kekurangan tersebut berasal dari guru dan anak. Diantaranya pada saat penggunaan media gambar berseri guru tidak mengatur dan mengkondisikan tempat duduk anak yang nyaman dan tidak membicarakan gambar satu demi satu dan mencari hubungan antara gambar-gambar. Sedangkan kekurangan dari anak yaitu tidak memperhatikan pelajaran guru, anak banyak bermain sendiri dan cepat bosan. Pada siklus II peningkatan kemampuan berbicara anak sudah mengalami perkembangan , dimana kekurangan-kekurangan yang terjadi pada siklus I sudah dapat diperbaiki dan dari 10 orang anak yang diteliti pada siklus II tidak ada lagi anak yang memperoleh nilai kategori kurang. Dengan demikian kemampuan berbicara anak melalui penggunaan media gambar berseri di Taman Kanak-Kanak Kartika Jaya XX-40 Parepare dapat meningkat

Strain engineering in alloy nanoparticles

The deformation of interatomic distances with respect to those of the perfect crystal generates atomic-level strain. In nanoalloys, strain can arise because of finite size, morphology, domain structure and lattice mismatch between their atomic compounds. Strain can strongly affect the functional properties of nanoalloys, as it alters their electronic energy levels. Moreover, atomic-level strain generates atomic-level stress, which in turn results in distortions induced by strain. When the stress accumulated in a nanoalloy exceeds a certain level, the particle can relax that stress by undergoing structural transitions such as shape and/or chemical ordering transitions. Atomic-level strain is then a powerful tool to control and manipulate the structural and functional properties of nanoalloys. This requires a combined theoretical and experimental approach both to deeply understand the physical origin of strain, and to characterize it with a sub-angstrom resolution. Here, we present a theoretical analysis of the main sources of strain in nanoalloys, we analyse how atomic-level strain can be experimentally measured with transmission electron microscopy, we discuss its effect on the functional properties of nanoalloys, finally we describe how atomic-level stress arises from atomic-level strain, and how stress can induce structural transformations at the nanoscale

Factores significantes de la anemia en niños menores de 5 años de edad, en los distritos del departamento de Lambayeque

La anemia es la deficiencia de hierro en sangre en las personas, es uno de los problemas nutricionales de mayor magnitud en el mundo, tanto en las áreas urbanas y rurales y en todos los estratos socioeconómicos. Es un problema generalizado en la población humana y específicamente, de consecuencias graves en la población vulnerable en niños menores de cinco. En la región Lambayeque la anemia, afecta principalmente en los distritos rurales; esto, ha conllevado a que el gobierno se preocupe por distribuir alguna ayuda básica para los niños. El propósito de la tesis es determinar los factores significantes de la anemia en niños menores de cinco años de edad en los distritos del departamento de Lambayeque. Mediante el diseño y aplicación de un modelo estructural se realizó una estimación econométrica para detectar los principales indicadores más significativos que la afectan la anemia, tomando como base los datos que se encuentra disponible en el INEI 2015 y en la Sub Región de salud de Lambayeque. Los resultados muestran que las variables que afectan la anemia en Lambayeque son: la pobreza monetaria (-1.43), la pobreza extrema (0.57), el no estudiar y no trabajar (1.96) y la población económicamente activa (4.64). El modelo tiene un R2 del 42% indica que las variables seleccionadas en conjunto cambian los niveles de anemia en 42% en los distritos del departamento de Lambayeque

Tuning the coalescence degree in the growth of Pt–Pd nanoalloys

Coalescence is a phenomenon in which two or more nanoparticles merge to form a single larger aggregate. By means of gas-phase magnetron-sputtering aggregation experiments on Pt-Pd nanoalloys, it is shown that the degree of coalescence can be tuned from a growth regime in which coalescence is negligible to a regime where the growth outcome is dominated by coalescence events. This transition is achieved by varying both the length of the aggregation zone and the pressure difference between the aggregation and the deposition chamber. In the coalescence-dominated regime, a wide variety of coalescing aggregates is produced and analyzed by TEM. The experimental results are interpreted with the aid of molecular-dynamics simulations. This allows to distinguish four different steps through which coalescence proceeds towards equilibrium. These steps, occurring on a hierarchy of well-separated time scales, consist in: (i) alignment of atomic columns; (ii) alignment of close-packed atomic planes; (iii) equilibration of shape; (iv) equilibration of chemical ordering

Shape control of size-selected naked platinum nanocrystals

Controlled growth of far-from-equilibrium-shaped nanoparticles with size selection is essential for the exploration of their unique physical and chemical properties. Shape control by wet-chemistry preparation methods produces surfactant-covered surfaces with limited understanding due to the complexity of the processes involved. Here, we report the controlled production and transformation of octahedra to tetrahedra of size-selected platinum nanocrystals with clean surfaces in an inert gas environment. Molecular dynamics simulations of the growth reveal the key symmetry-breaking atomic mechanism for this autocatalytic shape transformation, confirming the experimental conditions required. In-situ heating experiments demonstrate the relative stability of both octahedral and tetrahedral Pt nanocrystals at least up to 700 °C and that the extended surface diffusion at higher temperature transforms the nanocrystals into equilibrium shape

Frame-by-frame observations of structure fluctuations in single mass-selected Au clusters using aberration-corrected electron microscopy

The multi-dimensional potential energy surface (PES) of a nanoparticle, such as a bare cluster of metal atoms, controls both the structure and dynamic behaviour of the particle. These properties are the subject of numerous theoretical simulations. However, quantitative experimental measurements of critical PES parameters are needed to regulate the models employed in the theoretical work. Experimental measurements of parameters are currently few in number, while model parameters taken from bulk systems may not be suitable for nanosystems. Here we describe a new measurement methodology, in which the isomer structures of a single deposited nanocluster are obtained frame-by-frame in an aberration-corrected scanning transmission electron microscope (ac-STEM) in high angle annular dark field (HAADF) mode. Several gold clusters containing 309 ± 15 atoms were analysed individually after deposition from a mass-selected cluster source onto an amorphous carbon film. The main isomers identified are icosahedral (Ih), decahedral (Dh) and face-centred-cubic (fcc) (the bulk structure), alongside many amorphous (glassy) structures. The results, which are broadly consistent with static ac-STEM measurements of an ensemble of such clusters, open the way to dynamic measurements of many different nanoparticles of diverse sizes, shapes and compositions

Pathologic response and survival after neoadjuvant chemotherapy with or without pertuzumab in patients with HER2-positive breast cancer: the Neopearl nationwide collaborative study

PurposeClinical trials have shown a significant increase in pathologic complete response (pCR) with the addition of pertuzumab to neoadjuvant chemotherapy for patients with early-stage HER-2 positive breast cancer. To date, limited studies have examined comparative outcomes of neoadjuvant pertuzumab in real-world setting. The Neopearl study aimed to assess comparative real-life efficacy and safety of neoadjuvant pertuzumab for these patients.MethodsWe conducted a nationwide retrospective analysis involving 17 oncology facilities with a certified multidisciplinary breast cancer treatment committee. We identified patients with HER-2 positive stage II-III breast cancer treated with neoadjuvant chemotherapy based on trastuzumab and taxanes with or without pertuzumab. All patients underwent breast surgery and received a comprehensive cardiologic evaluation at baseline and after neoadjuvant treatment. Patients who received the combination of pertuzumab, trastuzumab, and chemotherapy constituted case cohort (PTCT), whereas those treated with trastuzumab and chemotherapy accounted for control cohort (TCT). The pCR rate and 5-year event free survival (EFS) were the primary outcomes. Secondary end-points were rates of conversion from planned modified radical mastectomy (MRM) to breast conservation surgery (BCS) and cardiotoxicities.ResultsFrom March 2014 to April 2021, we included 271 patients, 134 (49%) and 137 (51%) in TCT and PTCT cohort, respectively. Positive axillary lymph nodes and stage III were more frequent in PTCT cohort. The pCR rate was significantly increased in patients who received pertuzumab (49% vs 62%; OR 1.74, 95%CI 1.04-2.89) and with HER-2 enriched subtypes (16% vs 85%; OR 2.94, 95%CI 1.60-5.41). After a median follow-up of 5 years, the 5-year EFS was significantly prolonged only in patients treated with pertuzumab (81% vs 93%; HR 2.22, 95%CI 1.03-4.79). The same analysis performed on propensity score matched population showed concordant results. On univariate analysis, only patients with positive lymph nodes were found to benefit from pertuzumab for both pCR and 5-year EFS. The rates of conversion from MRM to BCS and cardiologic toxicities did not differ between the cohorts.ConclusionOur findings support previous data on improved outcomes with the addition of pertuzumab to trastuzumab-based neoadjuvant chemotherapy. This benefit seems to be more significant in patients with clinically positive lymph nodes

Colorectal Cancer Stage at Diagnosis Before vs During the COVID-19 Pandemic in Italy

IMPORTANCE Delays in screening programs and the reluctance of patients to seek medical attention because of the outbreak of SARS-CoV-2 could be associated with the risk of more advanced colorectal cancers at diagnosis. OBJECTIVE To evaluate whether the SARS-CoV-2 pandemic was associated with more advanced oncologic stage and change in clinical presentation for patients with colorectal cancer. DESIGN, SETTING, AND PARTICIPANTS This retrospective, multicenter cohort study included all 17 938 adult patients who underwent surgery for colorectal cancer from March 1, 2020, to December 31, 2021 (pandemic period), and from January 1, 2018, to February 29, 2020 (prepandemic period), in 81 participating centers in Italy, including tertiary centers and community hospitals. Follow-up was 30 days from surgery. EXPOSURES Any type of surgical procedure for colorectal cancer, including explorative surgery, palliative procedures, and atypical or segmental resections. MAIN OUTCOMES AND MEASURES The primary outcome was advanced stage of colorectal cancer at diagnosis. Secondary outcomes were distant metastasis, T4 stage, aggressive biology (defined as cancer with at least 1 of the following characteristics: signet ring cells, mucinous tumor, budding, lymphovascular invasion, perineural invasion, and lymphangitis), stenotic lesion, emergency surgery, and palliative surgery. The independent association between the pandemic period and the outcomes was assessed using multivariate random-effects logistic regression, with hospital as the cluster variable. RESULTS A total of 17 938 patients (10 007 men [55.8%]; mean [SD] age, 70.6 [12.2] years) underwent surgery for colorectal cancer: 7796 (43.5%) during the pandemic period and 10 142 (56.5%) during the prepandemic period. Logistic regression indicated that the pandemic period was significantly associated with an increased rate of advanced-stage colorectal cancer (odds ratio [OR], 1.07; 95%CI, 1.01-1.13; P = .03), aggressive biology (OR, 1.32; 95%CI, 1.15-1.53; P < .001), and stenotic lesions (OR, 1.15; 95%CI, 1.01-1.31; P = .03). CONCLUSIONS AND RELEVANCE This cohort study suggests a significant association between the SARS-CoV-2 pandemic and the risk of a more advanced oncologic stage at diagnosis among patients undergoing surgery for colorectal cancer and might indicate a potential reduction of survival for these patients

Outcomes from elective colorectal cancer surgery during the SARS-CoV-2 pandemic

This study aimed to describe the change in surgical practice and the impact of SARS-CoV-2 on mortality after surgical resection of colorectal cancer during the initial phases of the SARS-CoV-2 pandemic