Quadratic maps between modules

We introduce a notion of $R$-quadratic maps between modules over a commutative ring $R$ which generalizes several classical notions arising in linear algebra and group theory. On a given module $M$ such maps are represented by $R$-linear maps on a certain module $P^2_R(M)$. The structure of this module is described in term of the symmetric tensor square $Sym^2_R(M)$, the degree 2 component $\Gamma^2_R(M)$ of the divided power algebra over $M$, and the ideal $I_2$ of $R$ generated by the elements $r^2-r$, $r\in R$. The latter is shown to represent quadratic derivations on $R$ which arise in the theory of modules over square rings. This allows to extend the classical notion of nilpotent $R$-group of class 2 with coefficients in a 2-binomial ring $R$ to any ring $R$. We provide a functorial presentation of $I_2$ and several exact sequences embedding the modules $P^2_R(M)$ and $\Gamma^2_R(M)$.Comment: 22 page

Two-phase working fluids for the temperature range of 50 to 350 deg, phase 2

Several two phase heat transfer fluids were tested in aluminum and carbon steel reflux capsules for over 25,000 hours at temperatures up to 300 C. Several fluids showed very good stability and would be useful for long duration heat transfer applications over the range 100 to 350 C. Instrumentation for the measurement of surface tension and viscosity were constructed for use with heat transfer fluids over the temperature range 0 to 300 C and with pressures from 0 to 10 atmospheres. The surface tension measuring device constructed requires less than a 1.0 cc sample and displays an accuracy of about 5 percent in preliminary tests, while the viscometer constructed for this program requires a 0.05 cc sample and shows an accuracy of about 5 percent in initial tests

High-performance heat pipes for heat recovery applications

Methods to improve the performance of reflux heat pipes for heat recovery applications were examined both analytically and experimentally. Various models for the estimation of reflux heat pipe transport capacity were surveyed in the literature and compared with experimental data. A high transport capacity reflux heat pipe was developed that provides up to a factor of 10 capacity improvement over conventional open tube designs; analytical models were developed for this device and incorporated into a computer program HPIPE. Good agreement of the model predictions with data for R-11 and benzene reflux heat pipes was obtained

Scaffolding protein CcmM directs multiprotein phase separation in beta-carboxysome biogenesis

Biochemical, biophysical and structural analysis reveals how the scaffolding protein CcmM recruits the enzymes Rubisco and carbonic anhydrase into a condensate for encapsulation into carboxysomes-microcompartments in cyanobacteria that serve to optimize CO2 assimilation. Carboxysomes in cyanobacteria enclose the enzymes Rubisco and carbonic anhydrase to optimize photosynthetic carbon fixation. Understanding carboxysome assembly has implications in agricultural biotechnology. Here we analyzed the role of the scaffolding protein CcmM of the beta-cyanobacterium Synechococcus elongatus PCC 7942 in sequestrating the hexadecameric Rubisco and the tetrameric carbonic anhydrase, CcaA. We find that the trimeric CcmM, consisting of gamma CAL oligomerization domains and linked small subunit-like (SSUL) modules, plays a central role in mediation of pre-carboxysome condensate formation through multivalent, cooperative interactions. The gamma CAL domains interact with the C-terminal tails of the CcaA subunits and additionally mediate a head-to-head association of CcmM trimers. Interestingly, SSUL modules, besides their known function in recruiting Rubisco, also participate in intermolecular interactions with the gamma CAL domains, providing further valency for network formation. Our findings reveal the mechanism by which CcmM functions as a central organizer of the pre-carboxysome multiprotein matrix, concentrating the core components Rubisco and CcaA before beta-carboxysome shell formation

Stoffwechselveränderungen und Ernährungstherapie von Patienten nach großen viszeralchirurgischen Eingriffen und bei chirurgischen Intensivpatienten

Changes of Metabolism and Nutrition Therapy in Patients with Major Visceral Surgical Interventions and in Surgical Intensive Care Patients Surgical injury results in a variety of hormonal and immunologic reactions causing characteristic temporary metabolic changes (hyperglycemia, muscle protein catabolism). Although useful during the dawn of mankind, these metabolic changes are counterproductive in times of modern medicine. Perioperative nutrition tends to limit such secondary metabolic complications as much as possible, thereby improving patient prognosis. The cornerstone of each nutritional therapy is the supplementation of sufficient amounts of protein or amino acids (1.2-1.5 g/kg/day). Furthermore, hyperglycemia (>180 mg/dl) should be prevented by reducing the provision of carbohydrates during the postoperative acute phase. Oral/enteral nutrition should always be the application mode of choice. It is essential, however, that the upper and lower gastrointestinal tract is functioning properly. Therefore, a close surveillance regarding a potential deterioration of motility as well as absorption is mandatory. Quantity and quality of oral/enteral foods depends on the particularities of the surgical procedure. Patients with malignant diseases will profit from a preoperative nutritional conditioning (immunonutrition). Only patients with gastrointestinal dysfunction, who are simultaneously malnourished, benefit from postoperative parenteral nutrition. Malnutrition can be identified preoperatively by subjective global assessment. During parenteral nutrition, it is particularly important to closely monitor concentrations of blood glucose, triglycerides, and electrolytes. In critically ill patients, additional glutamine should be provided during all periods of parenteral substrate supply, whereas supplementation of intravenous fat is restricted to patients requiring a prolonged parenteral nutrition

Plant RuBisCo assembly in E. coli with five chloroplast chaperones including BSD2

Plant RuBisCo, a complex of eight large and eight small subunits, catalyzes the fixation of CO2 in photosynthesis. The low catalytic efficiency of RuBisCo provides strong motivation to reengineer the enzyme with the goal of increasing crop yields. However, genetic manipulation has been hampered by the failure to express plant RuBisCo in a bacterial host. We achieved the functional expression of Arabidopsis thaliana RuBisCo in Escherichia coli by coexpressing multiple chloroplast chaperones. These include the chaperonins Cpn60/Cpn20, RuBisCo accumulation factors 1 and 2, RbcX, and bundle-sheath defective-2 (BSD2). Our structural and functional analysis revealed the role of BSD2 in stabilizing an end-state assembly intermediate of eight RuBisCo large subunits until the small subunits become available. The ability to produce plant RuBisCo recombinantly will facilitate efforts to improve the enzyme through mutagenesis

Magnetic free energy at elevated temperatures and hysteresis of magnetic particles

We derive a free energy for weakly anisotropic ferromagnets which is valid in the whole temperature range and interpolates between the micromagnetic energy at zero temperature and the Landau free energy near the Curie point T_c. This free energy takes into account the change of the magnetization length due to thermal effects, in particular, in the inhomogeneous states. As an illustration, we study the thermal effect on the Stoner-Wohlfarth curve and hysteresis loop of a ferromagnetic nanoparticle assuming that it is in a single-domain state. Within this model, the saddle point of the particle's free energy, as well as the metastability boundary, are due to the change in the magnetization length sufficiently close to T_c, as opposed to the usual homogeneous rotation process at lower temperatures.Comment: 16 pages, 4 figure