Use Of K1 Research Articles

Spectrophotometric determination of the bicarbonate dissociation constant in seawater

The aqueous carbon dioxide (CO2) system stoichiometric dissociation constants K1 and K2 express the relative concentrations of CO2, HCO3− (bicarbonate), and CO32− (carbonate) in terms of pH. These constants are critical in the study of seawater and the oceans because any mathematical expression that relates the four major CO2 system parameters (pH, here expressed on the total hydrogen ion concentration scale, pHT; total dissolved inorganic carbon, CT; total alkalinity, AT; and CO2 fugacity, fCO2) requires the use of K1 and K2. Uncertainties associated with current characterizations of pK1 and pK2 (where pK = −log K), on the order of 0.01 and 0.02, limit the accuracy of marine CO2 system calculations. This work reports the results of a spectrophotometric method to experimentally determine the product K1K2 over environmentally relevant ranges of temperature (288.15 ≤ T ≤ 308.15 K) and salinity (19.6 ≤ Sp ≤ 41) where Sp denotes the practical salinity scale. Using previously published parameterizations of K1, values of pK2 could then be calculated from the new K1K2 values. The resulting set of pK2 values was fitted as a function of Sp and T to obtain a new pK2 parameterization (denoted as SWpK2) calculated with the K1 of Waters and Millero (2013) as revised by Waters et al. (2014): SWpK2 = 116.8067 − 3655.02 T−1 − 16.45817 ln T + 0.04523 Sp − 0.615 Sp0.5 − 0.0002799 Sp2 + 4.969 (Sp/T)The average root mean square deviation between the equation and the observed data is 0.003. Residuals of this pK2 fitting function (i.e., measured pK2 minus parameterized pK2) are substantially smaller than the residuals obtained in previous works. Similarly, the total standard uncertainty in pK2 is reduced from 0.015 (previous characterizations) to 0.010 (this work). Internal consistency assessments (comparisons of measured versus calculated values of AT, CT, pHT, and fCO2) were used to evaluate the computational utility of the new K2 parameterization. Assessments from both laboratory and shipboard data indicate that the internal consistency of CO2 system calculations is improved using the K2 parameterization of this work. This new K2 parameterization provides the most precise, and potentially the most accurate, bicarbonate dissociation constant characterization presently available for open ocean conditions.

Sol–gel synthesis of K1.33Mn8O16 nanorods and their applications for aqueous K-ion hybrid supercapacitors

K1.33Mn8O16 nanorods were successfully prepared by a facile sol–gel method with KHCO3, Mn(Ac)2 and citrate acid as raw materials. The cyclic voltammetry results demonstrate that the K1.33Mn8O16 nanorods exhibit a quasi-reversible K+ intercalation/deintercalation behavior in a 0.5 M K2SO4 aqueous solution. It has also been found that the assembled activated carbon (AC)//K1.33Mn8O16 asymmetric hybrid supercapacitor delivers an energy density of 17.74 Wh kg−1 at a power density of 210 W kg−1, and an energy density of 8.18 Wh kg−1 at a high power density of 2124 W kg−1. Moreover, the AC//K1.33Mn8O16 supercapacitor shows a good cycling property. To the best of our knowledge, the synthesis of K1.33Mn8O16 nanorods via the sol–gel route and the use of K1.33Mn8O16 in supercapacitors are reported for the first time.

Managing cutaneous side effects with K1 vitamine creme reduces cutaneous toxicities induced by cetuximab

20750 Background: Cetuximab is a chimeric IgG1 monoclonal antibody against the epidermal growth factor receptor, approved in the treatment of patients (pts) with metastatic colorectal cancer and head and neck squamous cell carcinoma. More than 80% of pts develop cutaneous reactions, mainly as acne-like rash or less frequently as pruritus, dry skin, desquamation, hypertrichosis or nail disorders. It is important to continue the therapy despite toxicity because delaying treatment and lowering doses typically reduce response rates. Methods: From September 2006 to August 2007, 30 pts with metastatic colorectal cancer were treated with cetuximab in combination with chemotherapy. They all suffered from acne-like rash. They were followed for at least 3 months, once per week. Skin care with topical use of creme containing urea and 0.1% K1 vitamin (Reconval K1) was started after the first documented cutaneous toxicity evaluated according to NCI CTCAE, ver.3. Results: Of 30 pts, 6 had grade 3 rush, 18 pts grade 2 and 6 pts grade 1. Reconval K1 was used twice daily. In all pts, cutaneous toxicity was gradually decreasing. The median time to improvement was 8 days and 18 days to observe down-staging in rash by at least 1 grade. In only 3 of 6 pts with grade 3 toxicity, reduction of cetuximab dose was needed, whereas in historical controls, in all pts with grade 3 skin toxicity, reduction of cetuximab dose was recommended and also performed. No dose reduction or delay of treatment was needed in the group of pts with grade 1 and 2 cutaneous toxicity. We didn’t observe any toxicity of topical use of Reconval K1. Conclusions: To our knowledge, this is the first documented effect of topical use of K1 vitamin creme for reducing cetuximab-induced cutaneous toxicity. Reconval K1 is useful in skin care of pts treated with cetuximab. Further studies are needed to evaluate the impact on response rate of cetuximab and quality of life. No significant financial relationships to disclose.

Hemodialysis Blood Access Flow Rates Can Be Estimated Accurately from On-Line Dialysate Urea Measurements and the Knowledge of Effective Dialyzer Urea Clearance

Measurement of blood flow rate (Qa) is used to monitor arteriovenous fistulas and grafts that are used for hemodialysis blood access. Most Qa measurements use indicator dilution techniques to measure the recirculation that is induced by the reversal of hemodialysis blood lines. R plus the dialysis circuit flow (Qb) allows the calculation of Qa. The principle of needle reversal also can be used with a dialysate urea monitor (e.g., DQM 200 [Gambro]) without injection of diluent; the effect of the reversal on urea concentration is observed. Access blood water flow rate (Qaw) in relation to the effective clearance (K) is found from the urea concentrations in the dialysate with needles in the normal (Cn) and reverse (Cr) positions: K/Qaw = (Cn - Cr)/Cr. Qa is calculated by adjusting Qaw for hematocrit and protein. For testing of this theoretical relationship, 20 patients who were dialyzed on Integra (Hospal) and Centrysystem 3 (Cobe) machines that were fitted with DQM 200 were studied. During each treatment, lines were reversed and Qa was measured by ultrasound velocity dilution (Transonic HD01 monitor); at the same time, Cn and Cr were measured by DQM 200 and K was calculated. K1 was determined from a predialysis blood urea concentration (Cb), initial dialysate urea concentration (Cd), dialysate flow rate (Qd), and the relationship K x Cb = Qd x Cd (K1). K was determined separately from a conductivity step method using Diascan (Hospal) attached to Integra machines only (K2). With the use of K1, 127 comparisons were made; a correlation existed (r = 0.916), although Bland-Altman analysis showed that the dialysate urea method gave a mean value 5.3% +/- 15.3 (+/-SD) higher than that of Transonic (P < 0.001). With the use of K2, there also was a correlation of (r = 0.944; n = 63), and Bland-Altman testing showed an NS difference of +3.5% between the dialysate urea and Transonic methods. Qa can be estimated from on-line dialysate urea measurements that are taken before and after line reversal together with knowledge of K.

Magnetocrystalline anisotropy and spin reorientation in Gd1−xDyxCo4B

Magnetic measurements at various temperatures have been performed for loose powder and field-oriented samples of Gd1−xDyxCo4B with x=0, 0.05, and 0.1. The temperature dependences of spontaneous magnetization in these compounds are determined. It is found that a spin reorientation occurs at around T=162 K for Gd0.95Dy0.05Co4B and at around 225 K for Gd0.9Dy0.1Co4B. The temperature dependences of magnetic anisotropy constants, K1(Gd1−xDyxCo4B), of Gd1−xDyxCo4B with x=0 and 0.1 are determined. The anomalous temperature dependence of K1 (GdCo4B) is well explained by taking account of the Gd sublattice magnetic anisotropy due to the dipole–dipole interaction and the Co sublattice magnetic anisotropy similar to that in YCo4B. The temperature dependence of the Dy sublattice magnetic anisotropy constant, K1(Dy), has also been determined by making use of K1(GdCo4B) and K1(Gd0.9Dy0.1Co4B).

Validation of a model for [1-11C]acetate as a tracer of cardiac oxidative metabolism

To develop a compartmental model for estimating myocardial oxygen consumption rate (MVO2) with [1-11C]acetate, the metabolic fate of radiolabeled acetate was determined in normoxic and ischemic conditions in isolated perfused rat hearts. Glutamate composed 63 +/- 1 and 44 +/- 7% of the total tissue radioactivity 2 min postinjection in normoxic and ischemic myocardium, respectively, and radiolabeled glutamate remained the largest fraction throughout 40 min of perfusion. Based on the biochemical pathway of the tracer and the temporal distribution of 14C-labeled metabolites, a six-compartment model was formulated. Studies using [1-11C]acetate and a pair of NaI detectors were then performed in the same perfused heart system to validate the model. Consistency between the model predictions and biochemical measurements of tissue and effluent metabolites supported the validity of the kinetic model in normoxic and ischemic conditions. Model-estimated MVO2 correlated well with experimentally measured MVO2 for normoxic, hypoxic, and ischemic conditions, with a slope of 0.97 (r = 0.95). In addition, the model-estimated rate constant, k42, which corresponded to the oxidative flux, correlated strongly with the myocardial clearance rate (k1 or kmono) determined from the tissue kinetics. These findings provide a mechanistic basis for the use of k1 or kmono as an index of MVO2 in both normoxic and ischemic myocardium studied with [1-11C]acetate and positron emission tomography.

Serotyping and genotyping of encapsulated Escherichia coli K1 sepsis isolates with a monoclonal IgG anti K1 antibody and K1 gene probes

Among infectious diseases caused by E. coli the capsular type K1 plays a predominant role. E. coli K1 isolates account for 80% of cases of E. coli neonatal meningitis and 30% of E. coli sepsis strains. Serotyping of K1 strains has conventionally relied upon the use of K1 -specific bacteriophages or serum agar methods with polyvalent anti K1 serum. In the study present here, 187 E. coli sepsis isolates have been analysed for production of the K1 antigen using K1 phages, K1 serum agar plates and Latex agglutination and ELISA using an IgG2a anti K1 monoclonal antibody. In total, 33 sepsis isolates (about 18%) were identified as K1 positive, with three of these strains proving negative in all tests except those exploiting the monoclonal antibody. That these three strains elaborate the K1 antigen was confirmed by Southern blot experiments using cloned K1 antigen production genes as probes. The failure of the three strains in all the tests except those that use monoclonal antibody could be explained by apparent disruption of K1 gene sequences that encode functions essential for the export of capsular material to the cell surface. The superiority of tests based on monoclonal antibodies above the conventional methods for detection of K1 antigen is evident.