Konstanz, Univ., Diplomarb., 2007.

Zugl.: Zürich, Techn. Hochsch., Diss., 2009

Stem diameter at breast height (D1.3m) and tree height (H) are commonly used measures of tree growth. Based on correlation analysis between biomass of stem, branches and leaves and stem diameter and height of tree we can identify allometric equation for predicting biomass and carbon sequestration of the vegetation. This study was carried out in the natural forests of Me Linh Station for biodiversity to develop allometric equation between biomass and diameter at breast height and height of tree. The study results indicated that twenty tree species dominate in natural forests in Me Linh Station for Biodiversity and they were selected for sampling. Through the 80 established linear equation models for above and below –ground biomass (AGB and BGB), we found that the biomass of tree species in Me Linh Station for Biodiversity were closely correlated with the diameter factor (R>0.902) and not clearly correlated with the height (correlation coefficient = 0.5498, R2< 0.549). Four regression equations were established, including: Pstem = 25.3051*(D1.3m)0.4627 (R2 : 9.661); Pbranch = 12.1043*( D1.3m)0.5416 (R2 : 9.8); Pleaves = 9.446*(D1.3m)0.5976 (R2 : 0.9363); P total biomass of forest = 25.882*D1.725 with R2: 0.8561) for estimating biomass and carbon sequestration of natural forest at the research site. / Đường kính ngang ngực (D1.3m) và chiều cao (H) cây là hai nhân tố thường được dùng để đánh giá sự phát triển của cây gỗ. Việc xây dựng các phương trình tương quan giữa sinh khối (SK) thân, cành, lá, sinh khối tầng cây gỗ, sinh khối của quần xã thực vật với đường kính và chiều cao cây góp phần rất lớn trong dự báo sinh khối và khả năng hấp thụ khí carbon của thảm thực vật. Kết quả nghiên cứu cho thấy 20 loài cây gỗ chiếm ưu thế trong rừng tự nhiên và chúng được chọn để thu mẫu. Mối tương quan giữa sinh khối với 2 nhân tố điều tra rừng là đường kính ngang ngực và chiều cao cây đã đươc kiểm tra thông qua 80 phương trình tương quan. Nhìn chung, sinh khối có tương quan chặt chẽ với nhân tố đường kính (hệ số tương quan R > 0,902), và không tương quan rõ với nhân tố chiều cao (R < 0,5498). Bốn phương trình tính sinh khối cho thảm rừng tại khu vực nghiên cứu đã được thiết lập: SKthân = 25,3051*(D1,3m)0,4627 (R2: 9,661); SKcành: 12,1043*(D1,3m)0,5416 (R2: 9,8); SKlá: 9,446*(D1,3m)0,5976 (R2: 0,9363) và SKtổng = 25,882*D1,725 with R2: 0,8561).

Um die komplexe Dynamik von Neuronen und deren Informationsverarbeitung mittels Pulssequenzen zu verstehen, ist es wichtig, die stationäre Puls-Aktivität zu charakterisieren. Die statistischen Eigenschaften von Pulssequenzen können durch vereinfachte stochastische Neuronenmodelle verstanden werden. Eine gut ausgearbeitete Theorie existiert für die Klasse der Erneuerungsmodelle, welche die statistische Unabhängigkeit der Interspike-Intervalle (ISI) annimmt. Experimente haben jedoch gezeigt, dass viele Neuronen Korrelationen zwischen ISIs aufweisen und daher nicht gut durch einen Erneuerungsprozess beschrieben werden. Solche Korrelationen können durch Nichterneuerungs-Modelle erfasst werden, welche jedoch theoretisch schlecht verstanden sind. Diese Arbeit ist eine analytische Studie von Nichterneuerungs-Modellen, die zwei bedeutende Korrelationsmechanismen untersucht: farbiges Rauschen, welches zeitlich-korrelierten Input darstellt, und negative Puls-Rückkopplung, welche Feuerraten-Adaption realisiert. Für das "Perfect-Integrate-and-Fire" (PIF) Modell, welchen durch ein allgemeines Gauss''sches farbiges Rauschen getrieben ist, werden die Statistiken höherer Ordnung der Output-Pulssequenz hergeleitet, insbesondere der Koeffizient der Variation, der serielle Korrelationskoeffizient (SCC), die ISI-Dichte und der Fano-Faktor. Weiterhin wird die Dynamik des PIF Modells mit Puls-getriggertem Adaptionsstrom und weissem Stromrauschen im Detail analysiert. Die Theorie liefert einen Ausdruck für den SCC, der für schwaches Rauschen aber beliebige Adaptions-Stärke und Zeitskale gültig ist, sowie die lineare Antwortfunktion und das Leistungsspektrum der Pulssequenz. Ausserdem wird gezeigt, dass ein stochastischer Adaptionsstrom wie ein langsames farbiges Rauschen wirkt, was ermöglicht, die dominierende Quellen des Rauschen in einer auditorischen Rezeptorzelle zu bestimmen. Schliesslich wird der SCC für das fluktuations-getriebene Feuerregime berechnet. / To understand the complex dynamics of neurons and its ability to process information using a sequence of spikes, it is vital to characterize its stationary spontaneous spiking activity. The statistical properties of spike trains can be explained by reduced stochastic neuron models that account for various sources of noise. A well-developed theory exists for the class of renewal models, in which the interspike intervals (ISIs) are statistically independent. However, experimental studies show that many neurons are not well described by a renewal process because of correlations between ISIs. Such correlations can be captured by generalized, non-renewal models, which are, however, poorly understood theoretically. This thesis represents an analytical study of non-renewal models, focusing on two prominent correlation mechanisms: colored-noise driving representing temporally correlated inputs, and negative feedback currents realizing spike-frequency adaptation. For the perfect integrate-and-fire (PIF) model driven by a general Gaussian colored noise input, the higher-order statistics of the output spike train is derived using a weak-noise analysis of the Fokker-Planck equation. This includes formulas for the coefficient of variation, the serial correlation coefficient (SCC), the ISI density and the Fano factor. Then, the dynamics of a PIF model with a spike-triggered adaptation and a white-noise current is analyzed in detail. The theory yields an expression for the SCC valid for weak noise but arbitrary adaptation strengths and time scale, and also provides the linear response to time-dependent stimuli and the spike train power spectrum. Furthermore, it is shown that a stochastic adaptation current acts like a slow colored noise, which permits to determine the source of spiking variability observed in an auditory receptor neuron. Finally, the SCC is calculated for the fluctuation-driven spiking regime by assuming discrete states of colored noise or adaptation current.

Phytoplankton samples were collected in 2016 during the dry and rainy seasons at nine sampling sites in Vinh Long province, Vietnam. Some basic environment parameters such as temperature, pH, dissolved oxygen, nitrate and phosphate were measured and a total of 209 phytoplankton species (six phyla, 96 genera) were identified. The phylum that had the greatest number of species was Bacillariophyta (82 species), followed by Chlorophyta (61 species), Cyanophyta (39 species), Euglenophyta (21 species), Chrysophyta (three species) and Dinophyta (three3 species). The phytoplankton density ranged from 4,128 to 123,029 cells/liter. The dominant algae recorded in the study area include Microcystis aeruginosa, Merismopedia glauca, Oscillatoria perornata, Jaaginema sp., Planktothrix agardhii, Coscinodiscus subtilis, Melosira granulata. In particular, Microcystis aeruginosa was the most density dominant species in the total number of sampling sites during the dry season survey, and this species was classified as a group producing toxins harmful to the environment. Surface water quality, according to QCVN 08: 2015/BTNMT was classified into Column A1 for pH, nitrate and Column B1 for dissolved oxygen, and Column B2 for phosphate. Phytoplankton community structure and environmental factors changed substantially between dry and rainy seasons. A Pearson (r) correlation coefficient was used for the relative analysis. The results indicated that the number of phytoplankton species were a significantly positive correlation with pH, dissolved oxygen and nitrate in the rainy season. The phytoplankton abundance was uncorrelated with environmental factors in both seasons. / Các mẫu thực vật phù du được thu thập trong năm 2016 (mùa khô và mùa mưa) tại 9 vị trí ở tỉnh Vĩnh Long, Việt Nam. Một số thông số môi trường như nhiệt độ, pH, oxy hòa tan, nitrat và phốt phát được đo ngay tại hiện trường. Tổng cộng 209 loài thực vật phù du được ghi nhận (6 ngành, 96 chi). Số lượng loài cao nhất là tảo Silic (82 loài), kế đến là tảo Lục (61 loài), tảo Lam (39 loài), tảo Mắt (21 loài), tảo Vàng ánh (3 loài) và tảo Giáp (3 loài). Mật độ thực vật phù du dao động từ 4.128 đến 123.029 tế bào/ lít. Các loài ưu thế ghi nhận được ở khu vực nghiên cứu gồm có: Microcystis aeruginosa, Merismopedia glauca, Oscillatoria perornata, Jaaginema sp., Planktothrix agardhii; Coscinodiscus subtilis, Melosira granulata. Trong đó, loài Microcystis aeruginosa chiếm ưu thế nhiều nhất trên tổng số điểm thu mẫu trong đợt khảo sát mùa khô, đồng thời loài này được xếp vào nhóm sản sinh độc tố gây hại cho môi trường. Chất lượng nước mặt theo QCVN 08:2015/BTNMT được xếp vào loại A1 đối với thông số pH, nitrat và loại B1 đối với thông số oxy hòa tan, và loại B2 đối với phốt phát. Cấu trúc quần xã thực vât nổi và các yếu tố môi trường thay đổi đáng kể giữa mùa mưa và mừa khô. Hệ số tương quan Pearson (r) được dùng để phân tích. Kết quả cho thấy số lượng thực vật phù du có tương quan thuận với pH, oxy hòa tan và nitrat trong mùa mưa và có ý nghĩa về mặt thống kê. Mật độ của thực vật phù du không tương quan với các yếu tố môi trường trong cả hai mùa.

Die vorliegende Arbeit beschäftigt sich mit Mechanismen, die in Einzelzellmodellen zu einer frequenzabhängigen Informationsübertragung führen können. Um dies zu untersuchen, werden Methoden aus der theoretischen Physik (Statistische Physik) und der Informationstheorie angewandt. Die Informationsfilterung in mehreren stochastischen Neuronmodellen, in denen unterschiedliche Mechanismen zur Informationsfilterung führen können, werden numerisch und, falls möglich, analytisch untersucht. Die Bandbreite der betrachteten Modelle erstreckt sich von reduzierten strombasierten ’Integrate-and-Fire’ (IF) Modellen bis zu biophysikalisch realistischeren leitfähigkeitsbasierten Modellen. Anhand numerischer Untersuchungen wird aufgezeigt, dass viele Varianten der IF-Neuronenmodelle vorzugsweise Information über langsame Anteile eines zeitabhängigen Eingangssignals übertragen. Der einfachste Vertreter der oben genannten Klasse der IF-Neuronmodelle wird dahingehend erweitert, dass ein Konzept von neuronalem ’Gedächtnis’, vermittelst positiver Korrelationen zwischen benachbarten Intervallen aufeinander- folgender Spikes, integriert wird. Dieses Model erlaubt eine analytische störungstheoretische Untersuchung der Auswirkungen positiver Korrelationen auf die Informationsfilterung. Um zu untersuchen, wie sich sogenannte ’unterschwelligen Resonanzen’ auf die Signalübertragung auswirken, werden Neuronenmodelle mit verschiedenen Nichtlinearitäten anhand numerischer Computersimulationen analysiert. Abschließend wird die Signalübertragung in einem neuronalen Kaskadensystem, bestehend aus linearen und nichtlinearen Elementen, betrachtet. Neuronale Nichtlinearitäten bewirken eine gegenläufige Abhängigkeit (engl. "trade-off") zwischen qualitativer, d.h. frequenzselektiver, und quantitativer Informations-übertragung, welche in allen von mir untersuchten Modellen diskutiert wird. Diese Arbeit hebt die Gewichtigkeit von Nichtlinearitäten in der neuronalen Informationsfilterung hervor. / Neurons transmit information about time-dependent input signals via highly non-linear responses, so-called action potentials or spikes. This type of information transmission can be frequency-dependent and allows for preferences for certain stimulus components. A single neuron can transmit either slow components (low pass filter), fast components (high pass filter), or intermediate components (band pass filter) of a time-dependent input signal. Using methods developed in theoretical physics (statistical physics) within the framework of information theory, in this thesis, cell-intrinsic mechanisms are being investigated that can lead to frequency selectivity on the level of information transmission. Various stochastic single neuron models are examined numerically and, if tractable analytically. Ranging from simple spiking models to complex conductance-based models with and without nonlinearities, these models include integrator as well as resonator dynamics. First, spectral information filtering characteristics of different types of stochastic current-based integrator neuron models are being studied. Subsequently, the simple deterministic PIF model is being extended with a stochastic spiking rule, leading to positive correlations between successive interspike intervals (ISIs). Thereafter, models are being examined which show subthreshold resonances (so-called resonator models) and their effects on the spectral information filtering characteristics are being investigated. Finally, the spectral information filtering properties of stochastic linearnonlinear cascade neuron models are being researched by employing different static nonlinearities (SNLs). The trade-off between frequency-dependent signal transmission and the total amount of transmitted information will be demonstrated in all models and constitutes a direct consequence of the nonlinear formulation of the models.

The variety of middle-class speakers in St. John’s conforms to some degree to mainland Canadian-English pronunciation norms, but in complex and distinctive ways (Clarke, 1985, 1991, 2010; D’Arcy, 2005; Hollett, 2006). One as yet unresolved question is whether speakers of this variety participate in the Canadian Shift (cf. Clarke, 2012; Chambers, 2012), a chain shift of the lax front vowels that has been confirmed for many different regions of Canada (e.g. Roeder and Gardner, 2013, for Thunder Bay and Toronto, Sadlier-Brown and Tamminga, 2008, for Halifax and Vancouver). While acoustic phonetic analyses of St. John’s English are rare, some claims have been made that urban St. John’s speakers do not participate in the shift, based on two or six speakers (Labov, Ash & Boberg, 2006; Boberg 2010). Other researchers with larger data sets suggest that younger St. John’s speakers participate in mainland Canadians innovations to different degrees than mainlanders (e.g. Hollett, 2006). The Canadian Shift has not been uniformly defined, but agreement exists that with the low-back merger in place, BATH/TRAP retracts and consequently DRESS lowers. Clarke et al. (1995), unlike Labov et al. (2006), assert that KIT is subsequently lowered. Boberg (2005, 2010), however, emphasizes retraction of KIT and DRESS and suggests unrelated parallel shifts instead. In this PhD thesis, I demonstrate the presence of the Canadian Shift in St. John’s, NL, conforming to Clarke et al.’s (1995) original proposal. In my stratified randomly-sampled data (approx. 10,000 vowels, 34 interviewees, stratified as to age, gender, socioeconomic status, and “local-ness”), results from Euclidean distance measures, correlation coefficients, and linear, as well as logistic, mixed-effects regression show that (1) young St. John’s speakers clearly participate in the shift; and that (2) age has the strongest and a linear effect. Continuous modeling of age yields even more significant results for participation in a classic chain shift (6% decrease in lowering per added year). My findings also confirm that the change seems to have entered the system via formal styles (cf. Clarke, 1991, 2010, for TRAP in St. John’s). Traditionally, the linguistic homogeneity on a phonetic level of the Canadian middle class has been explained by Canada’s settlement and migration patterns of the North American Loyalists from Ontario to the west (cf. Chambers, 2009). Newfoundland’s settlement is distinct, in that the British and the Irish were the only two relevant sources. If settlement were the only crucial reason for a shared pronunciation of Canada’s middle class from Vancouver to St. John’s, the Canadian Shift should be absent in the latter region. I suggest three reasons for middle-class St. John’s’ participation in the Canadian Shift: 1) Newfoundland’s 300-year-old rural-urban divide as a result of its isolation, through which British/Irish features are attributed to rural und lower social class speakers; 2) the development of the oil industry since the 1990’s, through which social networks changed according to the perception of social distance/closeness; and 3) the importance of the linguistic marketplace, which is high in St. John’s due to 1) and 2).

The variety of middle-class speakers in St. John’s conforms to some degree to mainland Canadian-English pronunciation norms, but in complex and distinctive ways (Clarke, 1985, 1991, 2010; D’Arcy, 2005; Hollett, 2006). One as yet unresolved question is whether speakers of this variety participate in the Canadian Shift (cf. Clarke, 2012; Chambers, 2012), a chain shift of the lax front vowels that has been confirmed for many different regions of Canada (e.g. Roeder and Gardner, 2013, for Thunder Bay and Toronto, Sadlier-Brown and Tamminga, 2008, for Halifax and Vancouver). While acoustic phonetic analyses of St. John’s English are rare, some claims have been made that urban St. John’s speakers do not participate in the shift, based on two or six speakers (Labov, Ash & Boberg, 2006; Boberg 2010). Other researchers with larger data sets suggest that younger St. John’s speakers participate in mainland Canadians innovations to different degrees than mainlanders (e.g. Hollett, 2006). The Canadian Shift has not been uniformly defined, but agreement exists that with the low-back merger in place, BATH/TRAP retracts and consequently DRESS lowers. Clarke et al. (1995), unlike Labov et al. (2006), assert that KIT is subsequently lowered. Boberg (2005, 2010), however, emphasizes retraction of KIT and DRESS and suggests unrelated parallel shifts instead. In this PhD thesis, I demonstrate the presence of the Canadian Shift in St. John’s, NL, conforming to Clarke et al.’s (1995) original proposal. In my stratified randomly-sampled data (approx. 10,000 vowels, 34 interviewees, stratified as to age, gender, socioeconomic status, and “local-ness”), results from Euclidean distance measures, correlation coefficients, and linear, as well as logistic, mixed-effects regression show that (1) young St. John’s speakers clearly participate in the shift; and that (2) age has the strongest and a linear effect. Continuous modeling of age yields even more significant results for participation in a classic chain shift (6% decrease in lowering per added year). My findings also confirm that the change seems to have entered the system via formal styles (cf. Clarke, 1991, 2010, for TRAP in St. John’s). Traditionally, the linguistic homogeneity on a phonetic level of the Canadian middle class has been explained by Canada’s settlement and migration patterns of the North American Loyalists from Ontario to the west (cf. Chambers, 2009). Newfoundland’s settlement is distinct, in that the British and the Irish were the only two relevant sources. If settlement were the only crucial reason for a shared pronunciation of Canada’s middle class from Vancouver to St. John’s, the Canadian Shift should be absent in the latter region. I suggest three reasons for middle-class St. John’s’ participation in the Canadian Shift: 1) Newfoundland’s 300-year-old rural-urban divide as a result of its isolation, through which British/Irish features are attributed to rural und lower social class speakers; 2) the development of the oil industry since the 1990’s, through which social networks changed according to the perception of social distance/closeness; and 3) the importance of the linguistic marketplace, which is high in St. John’s due to 1) and 2).:List of Tables viii List of Figures x 0 Prologue – Variationist Sociolinguistics 1 1 Introduction 27 2 English-speaking Canada and its Vowel Shifts 31 3 Newfoundland and its Englishes 77 4 Data and Methodology 107 5 Analysis and Discussion 243 6 Conclusion 363 Bibliography 375 Appendices 409 A Interview Questionnaire 409 B Normality Tests per Speaker and Age Group 423 C Vowel Plot of Median Formant Values 433 D Results for the Assumptions of T-tests 435 E Results from Decision Trees and Optimal Binning 439 F Results from Regression Analyses 449 G Résumé 457 H Deutsche Zusammenfassung der Dissertation 461 I Eidestattliche Erklärung zur Eigenständigkeit 469