Environmental constraints on cyanomyophage abundance in the subtropical Pacific Ocean

Viruses are abundant in the world’s oceans and are thought to be important participants in marine biogeochemical cycling. Of these viruses, cyanophages are considered especially important because they infect and lyse cyanobacteria, which are some of the main primary producers in marine environments. Cyanophages are thought to influence the abundance and diversity of cyanobacterial populations and impart significant mortality, thereby affecting primary productivity and microbial community structure. Despite their ecological relevance, little is known about how environmental factors shape cyanophage abundance and diversity over large temporal and spatial scales. To address this gap in knowledge, seawater samples were collected during a research cruise transect from Honolulu, HI to San Diego, CA. The Myoviridae family of cyanophage was targeted for this study because of its perceived ecological dominance and the availability of molecular probes which can be used to measure their diversity and quantify abundance. The g20 gene (which codes for portal vertex protein in myoviruses) was targeted by an established primer set and used as a proxy for cyanomyophage abundance in qPCR assays. Initial analysis of quantification data has revealed significant correlations between cyanomyophage abundance and depth, dissolved inorganic carbon concentration, and total viral abundance. Total viral abundance was also significantly correlated with depth. The lack of trends between viral abundance and other environmental variables may have been due to the temporal offset in the phage-host relationship, which needs to be taken into consideration in future studies

Quantitative identification of dynamical transitions in a semiconductor laser with optical feedback

Identifying transitions to complex dynamical regimes is a fundamental open problem with many practical applications. Semi- conductor lasers with optical feedback are excellent testbeds for studying such transitions, as they can generate a rich variety of output signals. Here we apply three analysis tools to quantify various aspects of the dynamical transitions that occur as the laser pump current increases. These tools allow to quantitatively detect the onset of two different regimes, low-frequency fluctuations and coherence collapse, and can be used for identifying the operating conditions that result in specific dynamical properties of the laser output. These tools can also be valuable for analyzing regime transitions in other complex systems.Peer ReviewedPostprint (published version

Margin reflex distance measure by computerized image processing in rigid contact lens wearers

OBJETIVO: Apresentar um método novo, baseado no processamento computadorizado de imagens, para quantificar a distância reflexo margem (MRD). MÉTODOS: Selecionamos para o estudo pacientes do Setor de Lentes de Contato do Serviço de Oftalmologia da Santa Casa de Porto Alegre que foram divididos em dois grupos: o primeiro foi composto por pacientes usuários de lentes de contato rígidas (63 olhos) e o segundo por pacientes que foram encaminhados para adaptação de lentes de contato sem história prévia de uso das mesmas (30 olhos). Todos os pacientes foram fotografados com o auxílio de uma câmera fotográfica digital (Nikon Coolpix 4300). A distância reflexo margem foi medida por processamento computadorizado de imagens utilizando o programa Image J. Foram excluídos do estudo pacientes submetidos a cirurgias intra-oculares ou palpebrais, pacientes apresentando ptose congênita e pacientes que ao exame biomicroscópico apresentavam conjuntivite papilar gigante. RESULTADOS: O método utilizado para quantificar distância reflexo margem parece bastante simples e aparentemente mais sensível e específico. O valor médio da distância reflexo margem no grupo caso foi 2,46 mm e no grupo controle 2,72 mm. Dessa forma, observou-se uma tendência de diminuir a distância reflexo margem com o uso de lentes rígidas, embora esses dados não tenham sido estatisticamente significativos (p=0,22). Observa-se também que os valores de distância reflexo margem apresentam uma variabilidade muito maior no grupo caso (41,46%) do que no controle (28,96%), que se apresenta mais homogêneo. CONCLUSÃO: Esse estudo introduziu uma metodologia inovadora para medir a distância reflexo margem utilizando o processamento computadorizado de imagens. Esse método é acessível e pode auxiliar no acompanhamento da distância reflexo margem de pacientes usuários de lentes de contato, especialmente rígidas.PURPOSE: To measure the MRD (margin reflex distance) in rigid contact lens wearers and controls by a new method, based on computerized image processing. METHOD: The patients were selected from the Contact Lens Sector of the Ophthalmology Service at the "Complexo Hospitalar Santa Casa de Porto Alegre", and they were divided into two groups: the first was formed of rigid contact lens wearers (63 eyes) and the second of patients without previous history of contact lens wear (30 eyes). All patients were photographed with a digital camera (Nikon Coolpix 4300). The margin reflex distance was measured by a computerized image processing using the Image J program. The study excluded patients that underwent any kind of intraocular or eyelid surgery, patients with congenital ptosis and patients with giant papillae conjunctivitis. RESULTS: The method utilized to measure margin reflex distance seems simple and more accurate. The average value of the margin reflex distance in the case group was 2.46 mm and in the control group 2.72 mm. The study shows that there is a tendency of decreasing the margin reflex distance with contact lens wear although the data were not statistically significant (p=0.22). The margin reflex distance values show a greater variability in the case group (41.46%) than in the control group (28.96%), that is more homogeneous. CONCLUSION: This study introduced a new method to measure the margin reflex distance using computerized image processing. This method is accessible and could help in follow-up of the margin reflex distance in contact lens wearers, specially those rigid

Quantifying the degree of locking in weakly forced stochastic systems

Controlling an stochastic nonlinear system with a small amplitude signal is a fundamental problem with many practical applications. Quantifying locking is challenging, and current methods, such as spectral or correlation analysis, do not provide a precise measure of the degree of locking. Here we study locking in an experimental system, consisting of a semiconductor laser with optical feedback operated in the regime where it randomly emits abrupt spikes. To quantify the locking of the optical spikes to small electric perturbations, we use two measures, the success rate (SR) and the false positive rate (FPR). The SR counts the spikes that are emitted shortly after each perturbation, while the FPR counts the additional extra spikes. We show that the receiver operating characteristic (ROC) curve (SR versus FPR plot) uncovers parameter regions where the electric perturbations fully control the laser spikes, such that the laser emits, shortly after each perturbation, one and only one spike. To demonstrate the general applicability of the ROC analysis we also study a stochastic bistable system under square-wave forcing and show that the ROC curve allows identifying the parameters that produce best locking.Peer ReviewedPostprint (author's final draft

Experimental study of modulation waveforms for entraining the spikes emitted by a semiconductor laser with optical feedback

© 2018 [Optical Society of America]. Users may use, reuse, and build upon the article, or use the article for text or data mining, so long as such uses are for non-commercial purposes and appropriate attribution is maintained. All other rights are reserved.The entrainment phenomenon, by which an oscillator adjusts its natural rhythm to an external periodic signal, has been observed in many natural systems. Recently, attention has focused on which are the optimal conditions for achieving entrainment. Here we use a semiconductor laser with optical feedback, operating in the low-frequency fluctuations (LFFs) regime, as a testbed for a controlled entrainment experiment. In the LFF regime the laser intensity displays abrupt spikes, which can be entrained to a weak periodic signal that directly modulates the laser pump current. We compare the performance of three modulation waveforms for producing 1:1 locking (one spike is emitted in each modulation cycle), as well as higher order locking regimes. We characterize the parameter regions where high-quality locking occurs, and those where the laser emits spikes which are not entrained to the external signal. The role of the modulation amplitude and frequency, and the role of the dc value of the laser pump current (that controls the natural spike frequency) in the entrainment quality are discussed.Peer ReviewedPostprint (published version

Experimental characterization of the transition to coherence collapse in a semiconductor laser with optical feedback

Semiconductor lasers with time-delayed optical feedback display a wide range of dynamical regimes, which have found various practical applications. They also provide excellent testbeds for data analysis tools for characterizing complex signals. Recently, several of us have analyzed experimental intensity time-traces and quantitatively identified the onset of different dynamical regimes, as the laser current increases. Specifically, we identified the onset of low-frequency fluctuations (LFFs), where the laser intensity displays abrupt dropouts, and the onset of coherence collapse (CC), where the intensity fluctuations are highly irregular. Here we map these regimes when both, the laser current and the feedback strength vary. We show that the shape of the distribution of intensity fluctuations (characterized by the standard deviation, the skewness, and the kurtosis) allows to distinguish among noise, LFFs and CC, and to quantitatively determine (in spite of the gradual nature of the transitions) the boundaries of the three regimes. Ordinal analysis of the interdropout time intervals consistently identifies the three regimes occurring in the same parameter regions as the analysis of the intensity distribution. Simulations of the well-known time-delayed Lang-Kobayashi model are in good qualitative agreement with the observations.Peer ReviewedPostprint (published version

Hubungan antara Sindroma Dispepsia dengan Pola Makan dan Jenis Kelamin pada Mahasiswa Fakultas Kedokteran Universitas Kristen Krida Wancana Angkatan 2013

Sindroma dispepsia fungsional merupakan kumpulan gejala yang terdiri atas nyeri ulu hati, mual, kembung, muntah, rasa cepat kenyang, dan sendawa. Tujuan penelitian ini untuk mengetahui karakteristik responden berdasarkan jenis kelamin dan pola makan, mengetahui gambaran sindroma dispepsia fungsional dan menganalisis hubungan antara pola makan serta jenis kelamin dengan sindroma dispepsia fungsional. Penelitian ini dilakukan di Fakultas Kedokteran (FK) Universitas Kristen Krida Wacana (Ukrida). Desain penelitian ini menggunakan pendekatan cross sectional analitik dengan 97 responden yang diambil secara simple random sampling. Data penelitian dianalisa dengan analisis bivariat dan univariat. Hasil penelitian ini, responden terbanyak adalah perempuan 61,9%, berpola makan tidak teratur 54,6%, dan gambaran sindrom dispepsia fungsional 57,7%. Hasil analisis hubungan antara pola makan dengan sindroma dispepsia fungsional yang mengalami sindroma dispepsia fungsional diperoleh 42 (79,2%) dari 53 responden yang pola makannya tidak teratur dan 14 (31,8%) dari 44 responden yang pola makannya teratur Hasil analisis hubungan antara jenis kelamin dengan sindrom dispepsia fungsional diperoleh 11 (29,7%) dari 37 responden laki-laki dan 45 orang (75,0%) dari 60 responden perempuan. Terdapat hubungan yang bermakna antara pola makan dan jenis kelamin mahasiswa angkatan 2013 dengan sindroma dispepsia fungsional (p < 0,001).Kata kunci : sindrom dispepsia fungsional, pola makan, jenis kelamin, mahasisw