Investigation of the possibility of exceeding the Greenwald density limit during ECRH in T-10

In T-10 experiments, attempts were made to significantly exceed the Greenwald limit $\bar n_{Gr} $ during high-power (P _ab=750 kW) electron-cyclotron resonance heating (ECRH) and gas puffing. Formally, the density limit $(\bar n_e )_{\lim } $ exceeding the Greenwald limit $({{(\bar n_e )_{\lim } } \mathord{\left/ {\vphantom {{(\bar n_e )_{\lim } } {\bar n_{Gr} }}} \right. \kern-0em} {\bar n_{Gr} }} = 1.8)$ was achieved for q _L=8.2. However, as q _L decreased, the ratio ${{(\bar n_e )_{\lim } } \mathord{\left/ {\vphantom {{(\bar n_e )_{\lim } } {\bar n_{Gr} }}} \right. \kern-0em} {\bar n_{Gr} }}$ also decreased, approaching unity at q _L≈3. It was suggested that the “current radius” (i.e., the radius of the magnetic surface enclosing the bulk of the plasma current I _p), rather than the limiter radius, was the parameter governing the value of $(\bar n_e )_{\lim } $ . In the ECRH experiments, no substantial degradation of plasma confinement was observed up to $\bar n_e \sim 0.9(\bar n_e )_{\lim } $ regardless of the ratio ${{(\bar n_e )_{\lim } } \mathord{\left/ {\vphantom {{(\bar n_e )_{\lim } } {\bar n_{Gr} }}} \right. \kern-0em} {\bar n_{Gr} }}$ . In different scenarios of the density growth up to $(\bar n_e )_{\lim } $ , two types of disruptions related to the density limit were observed.     

Retention of Dissolved Inorganic Nitrogen by Foliage and Twigs of Four Temperate Tree Species

Nitrogen (N) retention by tree canopies is believed to be an important process for tree nutrient uptake, and its quantification is a key issue in determining the impact of atmospheric N deposition on forest ecosystems. Due to dry deposition and retention by other canopy elements, the actual uptake and assimilation by the tree canopy is often obscured in throughfall studies. In this study, ¹⁵N-labeled solutions ( $ ^{15} {\text{NH}}_{4}^{ + } $ and $ ^{15} {\text{NO}}_{3}^{ - } $ ) were used to assess dissolved inorganic N retention by leaves/needles and twigs of European beech, pedunculate oak, silver birch, and Scots pine saplings. The effects of N form, tree species, leaf phenology, and applied $ {\text{NO}}_{3}^{ - } $ to $ {\text{NH}}_{4}^{ + } $ ratio on the N retention were assessed. Retention patterns were mainly determined by foliar uptake, except for Scots pine. In twigs, a small but significant ¹⁵N enrichment was detected for $ {\text{NH}}_{4}^{ + } $ , which was found to be mainly due to physicochemical adsorption to the woody plant surface. The mean $ {{^{15} {\text{NH}}_{4}^{ + } } \mathord{\left/ {\vphantom {{^{15} {\text{NH}}_{4}^{ + } } {^{15} {\text{NO}}_{3}^{ - } }}} \right. \kern-0em} {^{15} {\text{NO}}_{3}^{ - } }} $ retention ratio varied considerably among species and phenological stadia, which indicates that the use of a fixed ratio in the canopy budget model could lead to an over- or underestimation of the total N retention. In addition, throughfall water under each branch was collected and analyzed for $ ^{15} {\text{NH}}_{4}^{ + } $ , $ ^{15} {\text{NO}}_{3}^{ - } $ , and all major ions. Net throughfall of $ ^{15} {\text{NH}}_{4}^{ + } $ was, on average, 20 times higher than the actual retention of $ ^{15} {\text{NH}}_{4}^{ + } $ by the plant material. This difference in $ ^{15} {\text{NH}}_{4}^{ + } $ retention could not be attributed to pools and fluxes measured in this study. The retention of $ ^{15} {\text{NH}}_{4}^{ + } $ was correlated with the net throughfall of K⁺, Mg²⁺, Ca²⁺, and weak acids during leaf development and the fully leafed period, while no significant relationships were found for $ ^{15} {\text{NO}}_{3}^{ - } $ retention. This suggests that the main driving factors for $ {\text{NH}}_{4}^{ + } $ retention might be ion exchange processes during the start and middle of the growing season and passive diffusion at leaf senescence. Actual assimilation or abiotic uptake of N through leaves and twigs was small in this study, for example, 1–5% of the applied dissolved ¹⁵N, indicating that the impact of canopy N retention from wet deposition on forest productivity and carbon sequestration is likely limited.     

Longitudinal distribution of nitrate δ15N and δ18O in two contrasting tropical rivers: implications for instream nitrogen cycling

The longitudinal variations in the nitrogen (δ¹⁵N) and oxygen (δ¹⁸O) isotopic compositions of nitrate (NO₃ ^?), the carbon isotopic composition (δ¹³C) of dissolved inorganic carbon (DIC) and the δ¹³C and δ¹⁵N of particulate organic matter were determined in two Southeast Asian rivers contrasting in the watershed geology and land use to understand internal nitrogen cycling processes. The $ \delta^{15} {\text{N}}_{{{\text{NO}}_{3} }} $ became higher longitudinally in the freshwater reach of both rivers. The $ \delta^{18} {\text{O}}_{{{\text{NO}}_{3} }} $ also increased longitudinally in the river with a relatively steeper longitudinal gradient and a less cultivated watershed, while the $ \delta^{18} {\text{O}}_{{{\text{NO}}_{3} }} $ gradually decreased in the other river. A simple model for the $ \delta^{15} {\text{N}}_{{{\text{NO}}_{3} }} $ and the $ \delta^{18} {\text{O}}_{{{\text{NO}}_{3} }} $ that accounts for simultaneous input and removal of NO₃ ^? suggested that the dynamics of NO₃ ^? in the former river were controlled by the internal production by nitrification and the removal by denitrification, whereas that in the latter river was significantly affected by the anthropogenic NO₃ ^? loading in addition to the denitrification and/or assimilation. In the freshwater-brackish transition zone, heterotrophic activities in the river water were apparently elevated as indicated by minimal dissolved oxygen, minimal δ¹³C_DIC and maximal pCO₂. The δ¹⁵N of suspended particulate nitrogen (PN) varied in parallel to the $ \delta^{15} {\text{N}}_{{{\text{NO}}_{3} }} $ there, suggesting that the biochemical recycling processes (remineralization of PN coupled to nitrification, and assimilation of NO₃ ^?-N back to PN) played dominant roles in the instream nitrogen transformation. In the brackish zone of both rivers, the $ \delta^{15} {\text{N}}_{{{\text{NO}}_{3} }} $ displayed a declining trend while the $ \delta^{18} {\text{O}}_{{{\text{NO}}_{3} }} $ increased sharply. The redox cycling of NO₃ ^?/NO₂ ^? and/or deposition of atmospheric nitrogen oxides may have been the major controlling factor for the estuarine $ \delta^{15} {\text{N}}_{{{\text{NO}}_{3} }} $ and $ \delta^{18} {\text{O}}_{{{\text{NO}}_{3} }} $ , however, the exact mechanism behind the observed trends is currently unresolved.     

Long-term analysis of Hubbard Brook stable oxygen isotope ratios of streamwater and precipitation sulfate

In response to decreasing atmospheric emissions of sulfur (S) since the 1970s there has been a concomitant decrease in S deposition to watersheds in the Northeastern U.S. Previous study at the Hubbard Brook Experimental Forest, NH (USA) using chemical and isotopic analyzes ( $ \delta^{34} {\text{S}}_{{{\text{SO}}_{4} }} $ ) combined with modeling has suggested that there is an internal source of S within these watersheds that results in a net loss of S via sulfate in drainage waters. The current study expands these previous investigations by the utilization of δ¹⁸O analyzes of precipitation sulfate and streamwater sulfate. Archived stream and bulk precipitation samples at the Hubbard Brook Experimental Forest from 1968–2004 were analyzed for stable oxygen isotope ratios of sulfate ( $ \delta^{18} {\text{O}}_{{{\text{SO}}_{4} }} $ ). Overall decreasing temporal trends and seasonally low winter values of $ \delta^{18} {\text{O}}_{{{\text{SO}}_{4} }} $ in bulk precipitation are most likely attributed to similar trends in precipitation $ \delta^{18} {\text{O}}_{{{\text{H}}_{2} {\text{O}}}} $ values. Regional climate trends and changes in temperature control precipitation $ \delta^{18} {\text{O}}_{{{\text{H}}_{2} {\text{O}}}} $ values that are reflected in the $ \delta^{18} {\text{O}}_{{{\text{SO}}_{4} }} $ values of precipitation. The significant relationship between ambient temperature and the $ \delta^{18} {\text{O}}_{{{\text{H}}_{2} {\text{O}}}} $ values of precipitation is shown from a nearby site in Ottawa, Ontario (Canada). Although streamwater $ \delta^{18} {\text{O}}_{{{\text{SO}}_{4} }} $ values did not reveal temporal trends, a large difference between precipitation and streamwater $ \delta^{18} {\text{O}}_{{{\text{SO}}_{4} }} $ values suggest the importance of internal cycling of S especially through the large organic S pool and the concomitant effect on the $ \delta^{18} {\text{O}}_{{{\text{SO}}_{4} }} $ values in drainage waters.     

Studies on mass attenuation coefficient, effective atomic number and electron density of some vitamins

Mass attenuation coefficient, $ \mu_{m} $ , atomic cross-section, $ \sigma_{i} $ , electronic cross-section, $ \sigma_{e} $ , effective atomic number, $ Z_{\text{eff}} $ and effective electron density, $ N_{\text{el}} $ , were determined experimentally and theoretically for some vitamins (retinol, beta-carotene, thiamine, riboflavin, niacinamide, pantothenic acid, pyridoxine, biotin, folic acid, cyanocobalamin, ascorbic acid, cholecalciferol, alpha-tocopherol, ketamine, hesperidin) at 30.82, 59.54, 80.99, 356.61, 661.66 and 1,408.01?keV photon energies using a NaI(Tl) scintillation detector. The theoretical mass attenuation coefficients were estimated using mixture rules. The calculated values were compared with the experimental values for all vitamins.     

Obtain Quadruple Intense Plasmonic Resonances from Multilayered Gold Nanoshells by Silver Coating: Application in Multiplex Sensing

Four intense and separate localized surface plasmon resonance (LSPR) absorption peaks have been obtained in the gold-dielectric–gold–silver multilayer nanoshells. The silver coating on the gold shell results in a new LSPR peak at about 400 nm corresponding to the $ {{\left| {\omega_{+}^{-}} \right\rangle}_{Ag }} $ mode. The intense local electric field concentrated in the silver shell at the wavelength of 400 nm indicates that this new plasmonic band is coming from the symmetric coupling between the antibonding silver shell plasmon mode and the inner sphere plasmon. Increasing the silver shell thickness also leads to the intensity increasing of the $ {{\left| {\omega_{+}^{-}} \right\rangle}_{Au }} $ mode and blue shift of $ \left| {\omega_{-}^{+}} \right\rangle $ and $ \left| {\omega_{-}^{-}} \right\rangle $ modes. Therefore, quadruple intense plasmonic resonances in the visible region could be achieved in gold-dielectric–gold–silver multilayer nanoshells by tuning the geometrical parameters. And the quadruple intense plasmonic resonances in the visible region provide well potential for multiplex biosensing based on LSPR.     

Estimation of viscosity from passage time of liquids flowing through a microchannel array

Recently, a microchannel flow analyzer (MC-FAN) has been used to study the flow properties of blood. However, the correlation between blood passage time measured by use of the MC-FAN and hemorheology has not been clarified. In this study, a simple model is proposed for estimation of liquid viscosity from the passage time t _p of liquids. The t _p data for physiological saline were well represented by the model. According to the model, the viscosity of Newtonian fluids was estimated reasonably well from the t _p data. For blood samples, although the viscosity $ \eta_{\text{mc}} $ estimated from t _p was shown to be smaller than the viscosity $ \eta_{{450{\text{s}}^{ - 1} }} $ measured by use of a rotatory viscometer at a shear rate of 450 s^?1, $ \eta_{\text{mc}} $ was correlated with $ \eta_{{450{\text{s}}^{ - 1} }} $ . An empirical equation for estimation of $ \eta_{{450{\text{s}}^{ - 1} }} $ from $ \eta_{\text{mc}} $ of blood samples is proposed.     

The average local ionization energy as a tool for identifying reactive sites on defect-containing model graphene systems

In a continuing effort to further explore the use of the average local ionization energy $ \overline{\mathrm{I}}\left( \mathbf{r} \right) $ as a computational tool, we have investigated how well $ \overline{\mathrm{I}}\left( \mathbf{r} \right) $ computed on molecular surfaces serves as a predictive tool for identifying the sites of the more reactive electrons in several nonplanar defect-containing model graphene systems, each containing one or more pentagons. They include corannulene (C₂₀H₁₀), two inverse Stone-Thrower-Wales defect-containing structures C₂₆H₁₂ and C₄₂H₁₆, and a nanotube cap model C₂₂H₆, whose end is formed by three fused pentagons. Coronene (C₂₄H₁₂) has been included as a reference planar defect-free graphene model. We have optimized the structures of these systems as well as several monohydrogenated derivatives at the B3PW91/6-31G* level, and have computed their $ \overline{\mathrm{I}}\left( \mathbf{r} \right) $ on molecular surfaces corresponding to the 0.001 au, 0.003 au and 0.005 au contours of the electronic density. We find that (1) the convex sides of the interior carbons of the nonplanar models are more reactive than the concave sides, and (2) the magnitudes of the lowest $ \overline{\mathrm{I}}\left( \mathbf{r} \right) $ surface minima (the $ {{\overline{\mathrm{I}}}_{{\mathrm{S}\text{,}\min }}} $ ) correlate well with the interaction energies for hydrogenation at these sites. These $ {{\overline{\mathrm{I}}}_{{\mathrm{S}\text{,}\min }}} $ values decrease in magnitude as the nonplanarity of the site increases, consistent with earlier studies. A practical benefit of the use of $ \overline{\mathrm{I}}\left( \mathbf{r} \right) $ is that a single calculation suffices to characterize the numerous sites on a large molecular system, such as graphene and defect-containing graphene models.

Deriving fluorometer-specific values of relative PSI fluorescence intensity from quenching of F 0 fluorescence in leaves of Arabidopsis thaliana and Zea mays

The effect of stepwise increments of red light intensities on pulse-amplitude modulated (PAM) chlorophyll (Chl) fluorescence from leaves of A. thaliana and Z. mays was investigated. Minimum and maximum fluorescence were measured before illumination (F ₀ and F _M, respectively) and at the end of each light step ( $ F^{\prime}_{0} $ and $ F^{\prime}_{\text{M}} $ , respectively). Calculated $ F^{\prime}_{0} $ values derived from F ₀, F _M and $ F^{\prime}_{\text{M}} $ fluorescence according to Oxborough and Baker (1997) were lower than the corresponding measured $ F^{\prime}_{0} $ values. Based on the concept that calculated $ F^{\prime}_{0} $ values are under-estimated because the underlying theory ignores PSI fluorescence, a method was devised to gain relative PSI fluorescence intensities from differences between calculated and measured $ F^{\prime}_{0} $ . This method yields fluorometer-specific PSI data as its input data (F ₀, F _M, $ F^{\prime}_{0} $ and $ F^{\prime}_{\text{M}} $ ) depend solely on the spectral properties of the fluorometer used. Under the present conditions, the PSI contribution to F ₀ fluorescence was 0.24 in A. thaliana and it was independent on the light acclimation status; the corresponding value was 0.50 in Z. mays. Correction for PSI fluorescence affected Z. mays most: the linear relationship between PSI and PSII photochemical yields was clearly shifted toward the one-to-one proportionality line and maximum electron transport was increased by 50 %. Further, correction for PSI fluorescence increased the PSII reaction center-specific parameter, 1/F ₀ ? 1/F _M, up to 50 % in A. thaliana and up to 400 % in Z. mays.     

On the page number of RNA secondary structures with pseudoknots

Let ${\mathcal {S}}$ denote the set of (possibly noncanonical) base pairs {i, j} of an RNA tertiary structure; i.e. ${\{i, j\} \in \mathcal {S}}$ if there is a hydrogen bond between the ith and jth nucleotide. The page number of ${\mathcal {S}}$ , denoted ${\pi(\mathcal {S})}$ , is the minimum number k such that ${\mathcal {S}}$ can be decomposed into a disjoint union of k secondary structures. Here, we show that computing the page number is NP-complete; we describe an exact computation of page number, using constraint programming, and determine the page number of a collection of RNA tertiary structures, for which the topological genus is known. We describe an approximation algorithm from which it follows that ${\omega(\mathcal {S}) \leq \pi(\mathcal {S}) \leq \omega(\mathcal {S}) \cdot \log n}$ , where the clique number of ${\mathcal {S}, \omega(\mathcal {S})}$ , denotes the maximum number of base pairs that pairwise cross each other.     

The effects of temperature and exercise training on swimming performance in juvenile qingbo (Spinibarbus sinensis)

To investigate the effects of temperature and exercise training on swimming performance in juvenile qingbo (Spinibarbus sinensis), we measured the following: (1) the resting oxygen consumption rate $ \left( {{\dot{\text{M}}\text{O}}_{{ 2 {\text{rest}}}} } \right) $ , critical swimming speed (U _crit) and active oxygen consumption rate $ \left( {{\dot{\text{M}}\text{O}}_{{ 2 {\text{active}}}} } \right) $ of fish at acclimation temperatures of 10, 15, 20, 25 and 30 °C and (2) the $ \dot{M}{\text{O}}_{{ 2 {\text{rest}}}} $ , U _crit and $ \dot{M}{\text{O}}_{{ 2 {\text{active}}}} $ of both exercise-trained (exhaustive chasing training for 14 days) and control fish at both low and high acclimation temperatures (15 and 25 °C). The relationship between U _crit and temperature (T) approximately followed a bell-shaped curve as temperature increased: U _crit = 8.21/{1 + [(T ? 27.2)/17.0]²} (R ² = 0.915, P < 0.001, N = 40). The optimal temperature for maximal U _crit (8.21 BL s^?1) in juvenile qingbo was 27.2 °C. Both the $ \dot{M}{\text{O}}_{{ 2 {\text{active}}}} $ and the metabolic scope (MS, $ \dot{M}{\text{O}}_{{ 2 {\text{active}}}} - \dot{M}{\text{O}}_{{ 2 {\text{rest}}}} $ ) of qingbo increased with temperature from 10 to 25 °C (P < 0.05), but there were no significant differences between fish acclimated to 25 and 30 °C. The relationships between $ \dot{M}{\text{O}}_{{ 2 {\text{active}}}} $ or MS and temperature were described as $ {\dot{\text{M}}\text{O}}_{{ 2 {\text{active}}}} = 1,214.29/\left\{ {1 + \left[ {\left( {T - 28.8} \right)/10.6} \right]^{2} } \right\}\;\left( {R^{2} = 0.911,\;P < 0.001,\;N = 40} \right) $ and MS = 972.67/{1 + [(T ? 28.0)/9.34]²} (R ² = 0.878, P < 0.001, N = 40). The optimal temperatures for $ \dot{M}{\text{O}}_{{ 2 {\text{active}}}} $ and MS in juvenile qingbo were 28.8 and 28.0 °C, respectively. Exercise training resulted in significant increases in both U _crit and $ \dot{M}{\text{O}}_{{ 2 {\text{active}}}} $ at a low temperature (P < 0.05), but training exhibited no significant effect on either U _crit or $ \dot{M}{\text{O}}_{{ 2 {\text{active}}}} $ at a high temperature. These results suggest that exercise training had different effects on swimming performance at different temperatures. These differences may be related to changes in aerobic metabolic capability, arterial oxygen delivery, available dissolved oxygen, imbalances in ion fluxes and stimuli to remodel tissues with changes in temperature.     

Provenance variation and genetic parameters of Eucalyptus viminalis in Argentina

Genetic parameters for growth, stem straightness, pilodyn penetration, relative bark thickness and survival were estimated in a base-population of five open-pollinated provenance/progeny trials of Eucalyptus viminalis. The trials, located in northern, central and southern Buenos Aires Province, Argentina, comprised 148 open-pollinated families from 13 Australian native provenances and eight local Argentinean seedlots. The Australian native provenances come from a limited range of the natural distribution. Overall survival, based on the latest assessment of each trial, was 62.4%. Single-site analyses showed that statistically significant provenances differences (p?<?0.05) for at least one of the studied traits in three out of the five trials analyzed. The local land race performed inconsistently in this study. The average narrow-sense individual-tree heritability estimate $ \left( {{{\hat{h}}^2}} \right) $ was 0.27 for diameter and 0.17 for total height. Values of $ {\hat{h}^2} $ also increased with age. Pilodyn penetration, assessed at only one site, was more heritable $ \left( {{{\hat{h}}^2} = 0.32} \right) $ than the average of growth traits. Estimated individual-tree heritabilities were moderate to low for stem straightness (average of 0.20) and relative bark thickness (0.16). The estimated additive genetic correlations $ \left( {{{{r}}_{{A}}}} \right) $ between diameter and height were consistently high and positive ( $ {{r}_{^A}} $ average of 0.90). High additive genetic correlations were observed between growth variables and pilodyn penetration ( $ {{r}_{^A}} $ average of 0.58). Relative bark thickness showed a negative correlation with diameter $ \left( {{{{r}}_{^A}} = - 0.39} \right) $ and height $ \left( {{{{r}}_{^A}} = - 0.51} \right) $ . The average estimated additive genetic correlation between sites was high for diameter (0.67). The implications of all these parameter estimates for genetic improvement of E. viminalis in Argentina are discussed.     

Edge removal in random contact networks and the basic reproduction number

Understanding the effect of edge removal on the basic reproduction number ${\mathcal{R}_0}$ for disease spread on contact networks is important for disease management. The formula for the basic reproduction number ${\mathcal{R}_0}$ in random network SIR models of configuration type suggests that for degree distributions with large variance, a reduction of the average degree may actually increase ${\mathcal{R}_0}$ . To understand this phenomenon, we develop a dynamical model for the evolution of the degree distribution under random edge removal, and show that truly random removal always reduces ${\mathcal{R}_0}$ . The discrepancy implies that any increase in ${\mathcal{R}_0}$ must result from edge removal changing the network type, invalidating the use of the basic reproduction number formula for a random contact network. We further develop an epidemic model incorporating a contact network consisting of two groups of nodes with random intra- and inter-group connections, and derive its basic reproduction number. We then prove that random edge removal within either group, and between groups, always decreases the appropriately defined ${\mathcal{R}_0}$ . Our models also allow an estimation of the number of edges that need to be removed in order to curtail an epidemic.     

Heritability for resistance to Puccinia psidii Winter rust in Eucalyptus grandis Hill ex Maiden in Southwestern Brazil

The climates of the central and southern regions of São Paulo state in Brazil favor pathogens such as Puccinia psidii Winter, which causes a common and severe disease in Eucalyptus plantations under 2 years old. We studied genetic parameters including genotype by environment interaction (G × E) of resistance to P. psidii rust in Eucalyptus grandis at nine sites in São Paulo State. Open-pollinated progeny from ten ‘provenances’ were established in a randomized complete block design; at individual sites there were from 134 to 160 progenies, from four to eight blocks, and five to six trees per plot. Significant provenance and progeny(provenance) differences were detected, as was G × E involving progeny(provenance). However, the G × E involved little if any rank changes, indicating that selection can be done efficiently at a single site, if the disease level is sufficient. The estimated coefficient of genetic variation among the progeny within provenances $ \left( {{{{\widehat{\mathrm{CV}}}}_{\mathrm{g}}}} \right) $ was high and variable among the sites (ranging from 11 % to 36.7 %), demonstrating different expression of genetic variability among the sites. The estimated heritability at the individual-tree level $ \left( {{{\widehat{h}}^2}} \right) $ and within a plot $ \left( {\widehat{h}_{\mathrm{w}}^2} \right) $ ranged from low to intermediate (ranging from 0.04 to 0.46) and was high at the progeny-mean level $ \left( {\widehat{h}_{\mathrm{f}}^2} \right) $ (ranging from 0.30 to 0.86). Our study shows good prospects of controlling this disease by selection among and within progenies in a single site.     

Bone refilling in cortical basic multicellular units: insights into tetracycline double labelling from a computational model

Bone remodelling is carried out by ‘bone multicellular units’ ( $\text{ BMU }$ s) in which active osteoclasts and active osteoblasts are spatially and temporally coupled. The refilling of new bone by osteoblasts towards the back of the $\text{ BMU }$ occurs at a rate that depends both on the number of osteoblasts and on their secretory activity. In cortical bone, a linear phenomenological relationship between matrix apposition rate and $\text{ BMU }$ cavity radius is found experimentally. How this relationship emerges from the combination of complex, nonlinear regulations of osteoblast number and secretory activity is unknown. Here, we extend our previous mathematical model of cell development within a single cortical $\text{ BMU }$ to investigate how osteoblast number and osteoblast secretory activity vary along the $\text{ BMU }$ ’s closing cone. The mathematical model is based on biochemical coupling between osteoclasts and osteoblasts of various maturity and includes the differentiation of osteoblasts into osteocytes and bone lining cells, as well as the influence of $\text{ BMU }$ cavity shrinkage on osteoblast development and activity. Matrix apposition rates predicted by the model are compared with data from tetracycline double labelling experiments. We find that the linear phenomenological relationship observed in these experiments between matrix apposition rate and $\text{ BMU }$ cavity radius holds for most of the refilling phase simulated by our model, but not near the start and end of refilling. This suggests that at a particular bone site undergoing remodelling, bone formation starts and ends rapidly, supporting the hypothesis that osteoblasts behave synchronously. Our model also suggests that part of the observed cross-sectional variability in tetracycline data may be due to different bone sites being refilled by $\text{ BMU }$ s at different stages of their lifetime. The different stages of a $\text{ BMU }$ ’s lifetime (such as initiation stage, progression stage, and termination stage) depend on whether the cell populations within the $\text{ BMU }$ are still developing or have reached a quasi-steady state whilst travelling through bone. We find that due to their longer lifespan, active osteoblasts reach a quasi-steady distribution more slowly than active osteoclasts. We suggest that this fact may locally enlarge the Haversian canal diameter (due to a local lack of osteoblasts compared to osteoclasts) near the $\text{ BMU }$ ’s point of origin.