Jouni Heiskanen

Effects of cooling and internal wave motions on gas transfer coefficients in a boreal lake

Lakes and other inland waters contribute significantly to regional and global carbon budgets. Emissions from lakes are often computed as the product of a gas transfer coefficient, k 600 , and the difference in concentration across the diffusive boundary layer at the air–water interface. Eddy covariance (EC) techniques are increasingly being used in lacustrine gas flux studies and tend to report higher values for derived k 600 than other approaches. Using results from an EC study of a small, boreal lake, we modelled k 600 using a boundary-layer approach that included wind shear and cooling. During stratification, fluxes estimated by EC occasionally were higher than those obtained by our models. The high fluxes co-occurred with winds strong enough to induce deflections of the thermocline. We attribute the higher measured fluxes to upwelling-induced spatial variability in surface concentrations of CO2 within the EC footprint. We modelled the increased gas concentrations due to the upwelling and corrected our k 600 values using these higher CO2 concentrations. This approach led to greater congruence between measured and modelled k values during the stratified period. k 600 has a well-resolved and ~cubic relationship with wind speed when the water column is unstratified and the dissolved gases well mixed. During stratification and using the corrected k 600 , the same pattern is evident at higher winds, but k 600 has a median value of ~7 cm h−1 when winds are less than 6 m s−1, similar to observations in recent oceanographic studies. Our models for k 600 provide estimates of gas evasion at least 200% higher than earlier wind-based models. Our improved k 600 estimates emphasize the need for integrating within lake physics into models of greenhouse gas evasion.

Carbon dioxide and energy fluxes over a small boreal lake in Southern Finland

Dynamics of carbon dioxide and energy exchange over a small boreal lake were investigated. Flux measurements have been carried out by the eddy covariance technique during two open-water periods (June–October) at Lake Kuivajarvi in Finland. Sensible heat (H) flux peaked in the early morning, and upward sensible heat flux at night results in unstable stratification over the lake. Minimum H was measured in the late afternoon, often resulting in adiabatic conditions or slightly stable stratification over the lake. The latent heat flux (LE) showed a different pattern, peaking in the afternoon and having a minimum at night. High correlation (r2 = 0.75) between H and water-air temperature difference multiplied by wind speed (U) was found, while LE strongly correlated with the water vapor pressure deficit multiplied by U (r2 = 0.78). Monthly average values of energy balance closure ranged between 70 and 99%. The lake acted as net source of carbon dioxide, and the measured flux (FCO2) averaged over the two open-water periods (0.7 µmol m−2 s−1) was up to 3 times higher than those reported in other studies. Furthermore, it was found that during period of high wind speed (>3 m s−1) shear-induced water turbulence controls the water-air gas transfer efficiency. However, under calm nighttime conditions, FCO2 was poorly correlated with the difference between the water and the equilibrium CO2 concentrations multiplied by U. Nighttime cooling of surface water enhances the gas transfer efficiency through buoyancy-driven turbulent mixing, and simple wind speed-based transfer velocity models strongly underestimate FCO2.

Effects of water clarity on lake stratification and lake‐atmosphere heat exchange

Recent progress of including lake subroutines in numerical weather prediction (NWP) models has led to more accurate forecasts. In lake models, one essential parameter is water clarity, parameterized via the light extinction coefficient, Kd, for which a global constant value is usually used. We used direct eddy covariance fluxes and basic meteorological measurements coupled with lake water temperature and clarity measurements from a boreal lake to estimate the performance of two lake models, LAKE and FLake. These models represent two 1D modeling frameworks broadly used in NWP. The results show that the lake models are very sensitive to changes in Kd when it is lower than 0.5 m−1. The progress of thermal stratification depended strongly on Kd. In dark water simulations the mixed layer was shallower, longwave and turbulent heat losses higher and therefore the average water column temperatures lower than in clear water simulations. Thus, changes in water clarity can also affect the onset of ice cover. The more complex LAKE modeled the seasonal thermocline deepening whereas it remained virtually constant during summer in the FLake model. Both models overestimated the surface water temperatures by about 1°C and latent heat flux by >30%, but the variation in heat storage and sensible heat flux were adequately simulated. Our results suggest that, at least for humic lakes, a lake-specific, but not time-depending, constant value for Kd can be used and that a global mapping of Kd would be most beneficial in regions with relatively clear lakes, e.g. in lakes at high altitudes.

Blood stem cell mobilization and collection in patients with chronic lymphocytic leukaemia: a nationwide analysis

Some reports suggest that blood stem cell mobilization is difficult in a proportion of patients with CLL. We evaluated this issue in a large cohort of CLL patients. One hundred and twenty-eight patients with CLL underwent blood stem cell mobilization during 1995–2005 in Finland. Ninety-five percent of the patients had received fludarabine. The most common mobilization regimen was intermediate-dose CY plus G-CSF (90 patients, 70%). At least 2 × 106/kg CD34+ cells were collected after the first mobilization attempt in 83 patients (65%), whereas 45 patients (35%) failed to reach this collection target. No differences were observed between these patient groups with regard to age, time from the diagnosis to mobilization, number of previous treatment lines, number of fludarabine courses, time from the last fludarabine-containing chemotherapy to mobilization, disease status or degree of marrow infiltration. Patients who failed collection had platelets <100 × 109/l more commonly at the time of mobilization (30 vs 4%, P<0.001). A significant proportion of patients with CLL were difficult to mobilize. Adequate marrow function including platelet counts >100 × 109/l seem to be important factors in terms of successful blood stem cell collection.

A randomized phase II study of stem cell mobilization with cyclophosphamide+G-CSF or G-CSF alone after lenalidomide-based induction in multiple myeloma.

The most common means of mobilizing autologous stem cells is G-CSF alone or combined with cyclophosphamide (CY) to obtain sufficient CD34+ cells for one to two transplants. There are few prospective, randomized studies investigating mobilization regimens in multiple myeloma (MM), especially after lenalidomide-based induction. We designed this prospective, randomized study to compare low-dose CY 2 g/m2+G-CSF (arm A) and G-CSF alone (arm B) after lenalidomide-based up-front induction in MM. Of the 80 initially randomized patients, 69 patients were evaluable, 34 and 35 patients in arms A and B, respectively. The primary end point was the proportion of patients achieving a yield of ⩾3 × 106/kg CD34+ cells with 1−2 aphereses, which was achieved in 94% and 77% in arms A and B, respectively (P=0.084). The median number of aphereses needed to reach the yield of ⩾3 × 106/kg was lower in arm A than in arm B (1 vs 2, P=0.035). Two patients needed plerixafor in arm A and five patients in arm B (P=0.428). Although CY-based mobilization was more effective, G-CSF alone was successful in a great majority of patients to reach the defined collection target after three cycles of lenalidomide-based induction.

Different Apparent Gas Exchange Coefficients for CO2 and CH4: Comparing a Brown-Water and a Clear-Water Lake in the Boreal Zone during the Whole Growing Season.

The air-water exchange of carbon dioxide (CO2) and methane (CH4) is a central process during attempts to establish carbon budgets for lakes and landscapes containing lakes. Lake-atmosphere diffusive gas exchange is dependent on the concentration gradient between air and surface water and also on the gas transfer velocity, often described with the gas transfer coefficient k. We used the floating-chamber method in connection with surface water gas concentration measurements to estimate the gas transfer velocity of CO2 (kCO2) and CH4 (kCH4) weekly throughout the entire growing season in two contrasting boreal lakes, a humic oligotrophic lake and a clear-water productive lake, in order to investigate the earlier observed differences between kCO2 and kCH4. We found that the seasonally averaged gas transfer velocity of CH4 was the same for both lakes. When the lakes were sources of CO2, the gas transfer velocity of CO2 was also similar between the two study lakes. The gas transfer velocity of CH4 was constantly higher than that of CO2 in both lakes, a result also found in other studies but for reasons not yet fully understood. We found no differences between the lakes, demonstrating that the difference between kCO2 and kCH4 is not dependent on season or the characteristics of the lake.

Extracorporeal photopheresis in the treatment of acute graft-versus-host disease: a single-center experience: ECP FOR ACUTE GVHD

Steroid‐refractory acute graft‐versus‐host disease (aGVHD) is a serious complication after hematopoietic stem cell transplantation. The long‐term outcome of the patients is poor. Various immunosuppressive agents have been proposed as the second‐line therapy but none of them has turned out more effective than the others. Extracorporeal photopheresis (ECP) is a treatment option that does not predispose the patients to severe side effects of the immunosuppressive drugs.

Incidence and risk factors of secondary cancers after allogeneic stem cell transplantation: analysis of a single centre cohort with a long follow-up

As the long-term outcome of allogeneic stem cell transplantation (allo-SCT) has improved, the significance of post-transplant late effects is growing. In long-term survivors, secondary solid cancers have been reported to appear at least at twice the rate expected in the general population [1-4]. The reported cumulative incidence of secondary cancers varies from 1 to 11% at 10 years and from 2−12% at 15 years [1, 5, 6]. The 5-year overall survival (OS) rate from the diagnosis of a secondary malignancy is 42−50%, but the prognosis varies according to the type of the cancer [7, 8]. Risk factors for secondary cancers include the use of total body irradiation (TBI), the intensity of the conditioning regimen, chronic GvHD (cGvHD), and the age at transplantation, but the data are conflicting [1, 4, 6, 9] We investigated the incidence, the subtypes, and the risk factors of secondary cancers in patients aged over 16 who underwent allo-SCT in Helsinki University Hospital between January 1996 and December 2014. Patients with haploidentical donors, cord blood grafts, or double alloSCT (34 in total) were excluded. Cyclosporine A and methotrexate were used as GvHD prophylaxis. We included all secondary malignancies, except for post-transplant lymphoproliferation and non-melanoma skin cancers. The follow-up of the living patients was to the end of May 2017. The patient data were collected from the EBMT Promise database. The incidence rates of specific cancer types in Finland were obtained from the Finnish Cancer Registry, which maintains a database on cancers detected in Finland (population 5.5 million). Descriptive cross-tabulations were created between the response variable (incidence of secondary malignancy) and the predefined potential risk factors (age at transplantation, gender, diagnosis, conditioning intensity, TBI, anti-thymocyte globulin as a part of the conditioning, graft type, donor type, acute GvHD (aGvHD), aGvHD ≥ gr 2, cGvHD, and extensive cGvHD). The effect of the risk factors was first analysed with univariate logistic regression. Second, a multivariate logistic regression model was fitted, where the variables found meaningful (P value < 0.1) in the univariate analysis were inserted into the model as fixed terms. As both cGvHD (any grade) and extensive cGvHD were significant in the univariate analysis, only the one (cGvHD any grade) with the lower P value was included in the multivariate model. Odds ratios (OR) and their 95% CIs were used to quantify the results of the logistic regression models. The ORs are constructed for the probability for the secondary cancer to occur. The cumulative incidence of secondary cancers and OS were estimated by the Kaplan-Meier method where death or the end of the follow-up time were competitive events, whichever came first. The incidence rates of secondary cancers were evaluated by calculating the incidence rate per 100 000 person-years applying a formula: (number of events/sum of follow-up times in years of the sample population)*100 000. This approach was taken to be able to compare with rates from the Finnish Cancer Registry. The CIs for the incidence rates /100 000 person-years were calculated using a Poisson regression model. Standardised incidence ratios (SIR) of secondary cancers were calculated as the ratio of the observed incidence rates to the expected population incidence rates. P values of < 0.05 were considered statistically significant, all the presented P values are two-tailed. Statistical analyses were carried out with SAS for Windows (version 9.3; SAS Institute, Cary, NC, USA). * Eeva Martelin eeva.martelin@hus.fi

Diagnosis of veno-occlusive disease/sinusoidal obstruction syndrome of the liver: problems of interpretation.

Diagnosis of veno-occlusive disease/sinusoidal obstruction syndrome of the liver: problems of interpretation