Changes in physical and chemical variables

An article reviewing the work undertaken looking at the seasonal variation of chemical conditions in water at various depths in lakes. The laboratory tests undertaken for the research is outlined, as well as details of the sampling locations and the staff involved with the work. One figure shows the seasonal variation in the amounts of dissolved substances in the surface water of Windermere during 1936. Another figure shows seasonal varation inthe dry weight of phyto- and zooplankton in Windermere. Seasonal changes are discussed further and a table is included showing chemical conditions in winter and summer for Windermere

Liver regeneration in dogs: Morphologic and chemical changes

Forty-four percent and 72% hepatectomy were carried out in dogs and the animals were sacrificed for biochemical and pathologic studies from 0.5 to 6 days later. Compensatory hypertrophy and hyperplasia ("regeneration") were evident within 1 day, reached a maximum in 3 days, and were almost complete by 6 days. Coincident with the histologic events of regeneration were decreases in responsiveness of receptor adenyl cyclase to glucagon stimulation, increases of cyclic AMP, inconsistent changes in plasma insulin, and increases in plasma glucagon. These studies have standardized hepatic resection in dogs and they have focused attention upon some possible mechanisms that will require further study. © 1978 Academic Press, Inc. All rights of reserved

Changes of Physico–Chemical Properties of Pig Slurry During Storage

This study was aimed to determine changes of the characteristics of raw pig slurry as liquid organic fertilizer at various storage times. A completely randomized design was used in this research. The treatments were storage times, i.e.: 0, 15, 30, 45, and 60 days. Variables observed were loss of the slurry, degree of acidity (pH), electrical conductivity (EC), total solid (TS), volatile solid (VS), total chemical oxygen demand (tCOD), soluble chemical oxygen demand (sCOD), total nitrogen (TN), ammonia-nitrogen (NH3-N), nitrate-nitrogen (NO3-N), total phosphate (TP), and dissolve reactive phosphate (DRP). The results showed that storage time significantly affected all the observed variables, except the concentration of NO3-N and total phosphate content. The pH, TS, VS, DRP, and losses of slurry lost during storage times increased, while EC, TN, NH3-N, tCOD, and sCOD decreased. Physico-chemical properties of slurry during storage times changed, as a result of organic matter breakdown

Recent advances in experimental techniques to probe fast excited-state dynamics in biological molecules in the gas phase : dynamics in nucleotides, amino acids and beyond

In many chemical reactions, an activation barrier must be overcome before a chemical transformation can occur. As such, understanding the behaviour of molecules in energetically excited states is critical to understanding the chemical changes that these molecules undergo. Among the most prominent reactions for mankind to understand are chemical changes that occur in our own biological molecules. A notable example is the focus towards understanding the interaction of DNA with ultraviolet radiation and the subsequent chemical changes. However, the interaction of radiation with large biological structures is highly complex, and thus the photochemistry of these systems as a whole is poorly understood. Studying the gas-phase spectroscopy and ultrafast dynamics of the building blocks of these more complex biomolecules offers the tantalizing prospect of providing a scientifically intuitive bottom-up approach, beginning with the study of the subunits of large polymeric biomolecules and monitoring the evolution in photochemistry as the complexity of the molecules is increased. While highly attractive, one of the main challenges of this approach is in transferring large, and in many cases, thermally labile molecules into vacuum. This review discusses the recent advances in cutting-edge experimental methodologies, emerging as excellent candidates for progressing this bottom-up approach

Role of hydrodynamic flows in chemically driven droplet division

We study the hydrodynamics and shape changes of chemically active droplets. In non-spherical droplets, surface tension generates hydrodynamic flows that drive liquid droplets into a spherical shape. Here we show that spherical droplets that are maintained away from thermodynamic equilibrium by chemical reactions may not remain spherical but can undergo a shape instability which can lead to spontaneous droplet division. In this case chemical activity acts against surface tension and tension-induced hydrodynamic flows. By combining low Reynolds-number hydrodynamics with phase separation dynamics and chemical reaction kinetics we determine stability diagrams of spherical droplets as a function of dimensionless viscosity and reaction parameters. We determine concentration and flow fields inside and outside the droplets during shape changes and division. Our work shows that hydrodynamic flows tends to stabilize spherical shapes but that droplet division occurs for sufficiently strong chemical driving, sufficiently large droplet viscosity or sufficiently small surface tension. Active droplets could provide simple models for prebiotic protocells that are able to proliferate. Our work captures the key hydrodynamics of droplet division that could be observable in chemically active colloidal droplets

Helium nanodroplet isolation ro-vibrational spectroscopy: methods and recent results

In this article, recent developments in HElium NanoDroplet Isolation (HENDI) spectroscopy are reviewed, with an emphasis on the infrared region of the spectrum. Topics discussed include experimental details, comparison of radiation sources, symmetry issues of the helium solvation structure, sources of line broadening, changes in spectroscopic constants upon solvation, and applications including formation of novel chemical structures.Comment: 24 pages, 8 figures, 3 tables; to be published in the Journal of Chemical Physic

Clouds, photolysis and regional tropospheric ozone budgets.

We use a three-dimensional chemical transport model to examine the shortwave radiative effects of clouds on the tropospheric ozone budget. In addition to looking at changes in global concentrations as previous studies have done, we examine changes in ozone chemical production and loss caused by clouds and how these vary in different parts of the troposphere. On a global scale, we find that clouds have a modest effect on ozone chemistry, but on a regional scale their role is much more significant, with the size of the response dependent on the region. The largest averaged changes in chemical budgets (±10–14%) are found in the marine troposphere, where cloud optical depths are high. We demonstrate that cloud effects are small on average in the middle troposphere because this is a transition region between reduction and enhancement in photolysis rates. We show that increases in boundary layer ozone due to clouds are driven by large-scale changes in downward ozone transport from higher in the troposphere rather than by decreases in in-situ ozone chemical loss rates. Increases in upper tropospheric ozone are caused by higher production rates due to backscattering of radiation and consequent increases in photolysis rates, mainly J(NO2). The global radiative effect of clouds on isoprene, through decreases of OH in the lower troposphere, is stronger than on ozone. Tropospheric isoprene lifetime increases by 7% when taking clouds into account. We compare the importance of clouds in contributing to uncertainties in the global ozone budget with the role of other radiatively-important factors. The budget is most sensitive to the overhead ozone column, while surface albedo and clouds have smaller effects. However, uncertainty in representing the spatial distribution of clouds may lead to a large sensitivity of the ozone budget components on regional scales

Mineral Surface and Fluid Chemistry in Nakhlite Analog Water-Rock Reactions

We report on experiments with Mars analog materials under diagenetic conditions and find characteristic chemical surface changes in correspondence with the fluid conditions

Changes on the Physical-Chemical Properties of Kue Delapan Jam on Various Steaming TIME

This research intended to study browning reaction between glucose, fructose, and lipids with amino acids in real system during making Kue Delapan Jam. Research applied completely randomized design with steaming time as treatment ( 2, 4, 6, and 8 hours) with 3 replication. The development of color and browning index were ivestigated by using lightness, redness, yellowness, and total color difference (TCD) during reaction, and the absorbance of methanol extracts was measured at 420 nm in 40.0 mm silica. The development of texture was monitored by using Bookfield texture analyzer. Test results showed that steaming time influenced the color, browning index, texture, protein, and fat content of the cake significantly. Steaming time has no effect on water content. There were positive correlation between steaming time with TDC, redness, texture, and browning index during course. While for lightness, yellowness, pH, protein, and fat content indicated negative correlation. Changes on texture, TDC, browning index, protein, and fat content followed linear model