Silicon micromachined ultrasonic scalpel for the dissection and coagulation of tissue

This work presents a planar, longitudinal mode ultrasonic scalpel microfabricated from monocrystalline silicon wafers. Silicon was selected as the material for the ultrasonic horn due to its high speed of sound and thermal conductivity as well as its low density compared to commonly used titanium based alloys. Combined with a relatively high Young's modulus, a lighter, more efficient design for the ultrasonic scalpel can be implemented which, due to silicon batch manufacturing, can be fabricated at a lower cost. Transverse displacement of the piezoelectric actuators is coupled into the planar silicon structure and amplified by its horn-like geometry. Using finite element modeling and experimental displacement and velocity data as well as cutting tests, key design parameters have been identified that directly influence the power efficiency and robustness of the device as well as its ease of controllability when driven in resonance. Designs in which the full- and half-wave transverse modes of the transducer are matched or not matched to the natural frequencies of the piezoelectric actuators have been evaluated. The performance of the Si micromachined scalpels has been found to be comparable to existing commercial titanium based ultrasonic scalpels used in surgical operations for efficient dissection of tissue as well as coaptation and coagulation of tissue for hemostasis. Tip displacements (peak-to-peak) of the scalpels in the range of 10-50 μm with velocities ranging from 4 to 11 m/s have been achieved. The frequency of operation is in the range of 50-100 kHz depending on the transverse operating mode and the length of the scalpel. The cutting ability of the micromachined scalpels has been successfully demonstrated on chicken tissue.

Obesity, depression, and chronic low-grade inflammation in women with polycystic ovary syndrome

BACKGROUND AND OBJECTIVE

Women with polycystic ovary syndrome (PCOS) present with multiple risk factors for cardiovascular diseases at a young age, including obesity and chronic low-grade inflammation. Since depression is common in PCOS, this study aimed to address whether depression correlates with indices of chronic low-grade inflammation beyond the association with obesity.

METHODS

Serum concentrations of IL-6, the stimulated production of IFN-gamma, TNF-alpha, IL-2, IL-4, IL-5, and IL-10, leukocyte numbers, and hsCRP were analyzed in 57 PCOS patients and 28 healthy women, together with clinical parameters, including body mass index (BMI), testosterone, and insulin resistance (HOMA-IR), and psychological parameters, including Beck Depression Inventory (BDI) and health-related quality-of-life (SF-36) scores.

RESULTS

PCOS patients demonstrated significantly increased hsCRP, IL-6, and leukocyte numbers. Group differences in IL-6 and leukocyte numbers, but not hsCRP, disappeared after controlling for BMI. The stimulated production of IFN-gamma, TNF-alpha, IL-2, IL-4, and IL-5 was significantly decreased, irrespective of BMI. In PCOS, hsCRP, IL-6, and leukocyte numbers were correlated with BMI, HDL, diastolic blood pressure, and with insulin resistance. On the other hand, no correlations were found with depression scores or with PCOS-specific endocrine abnormalities. In regression models, BMI was a significant predictor of the key immune markers, and explained a large amount of variance, whereas BDI was not included in either model.

CONCLUSIONS

These data confirm that obesity plays a pivotal role in inflammatory processes relevant to cardiovascular risk in women with PCOS. However, even lean PCOS patients may display subtle alterations in specific aspects of immunity. Our findings did not support a correlation of depression with chronic low-grade inflammation in PCOS.

Test of a potential link between analytic and nonanalytic category learning and automatic, effortful processing

The link between automatic and effortful processing and nonanalytic and analytic category learning was evaluated in a sample of 29 college undergraduates using declarative memory, semantic category search, and pseudoword categorization tasks. Automatic and effortful processing measures were hypothesized to be associated with nonanalytic and analytic categorization, respectively. Results suggested that contrary to prediction strong criterion-attribute (analytic) responding on the pseudoword categorization task was associated with strong automatic, implicit memory encoding of frequency-of-occurrence information. Data are discussed in terms of the possibility that criterion-attribute category knowledge, once established, may be expressed with few attentional resources. The data indicate that attention resource requirements, even for the same stimuli and task, vary depending on the category rule system utilized. Also, the automaticity emerging from familiarity with analytic category exemplars is very different from the automaticity arising from extensive practice on a semantic category search task. The data do not support any simple mapping of analytic and nonanalytic forms of category learning onto the automatic and effortful processing dichotomy and challenge simple models of brain asymmetries for such procedures.

Lifting of the degeneracy in semibullvalenes by remote and direct substituents: a quantitative study using variable-temperature carbon-13 NMR spectroscopy

A series of six 1,5-(ethylmethyl)semibullvalenes (1a <==> 1a', 2 <==> 2', 3 <==>3') and two 4(2)-substituted semibullvalenes (4 <==> 4'), each undergoing Cope equilibria between nondegenerate valence tautomers, was investigated by carbon-13 NMR spectroscopy at a range of temperatures in several different solvents. Gompper's treatment of substituent perturbation was extended, specifically accounting for the effects of the substituents on chemical shifts, to allow the determination of the thermodynamic parameters for these skewed equilibria. These new treatments were used to determine the population difference (f - f ') between the valence tautomers and the perturbation thermodynamic quantities DeltaH(P), DeltaS(P), and DeltaG(P). The slow-exchange limit was reached for the parent 1,5-(ethylmethyl)semibullvalenes 3a <==> 3a' from which it was established that the preferred valence tautomer is 3a with the ethyl group on the cyclopropane ring. Despite considerable effort, the slow-exchange limit could not be reached in any of our other remotely substituted semibullvalenes. Provided that the ethyl group always prefers the cyclopropyl position as in 3a, the 1-ethyl-5-methylsemibullvalenes 1a, 2, and 3 are more stable by DeltaH(P) = 0.7-1.7 kJ mol(-1) than their valence tautomers 1a', 2', and 3'. In the directly substituted semibullvalenes (4 left harpoon ovet right harpoon 4'), the preferred valence tautomers 4a and 4b have the bromine atom or the nitrile group on the vinyl position (C(4)) rather than on the cyclopropane ring (C(2)) and are more stable than 4a' and 4b' by DeltaH(P) = 4.8 and 7.0 kJ mol(-1), respectively.

Effects of population and affluence on CO2 emissions

We developed a stochastic version of the Impact = Population x Affluence x Technology (IPAT) model to estimate the effects of population, affluence, and technology on national CO2 emissions. Our results suggest that, for population, there are diseconomies of scale for the largest nations that are not consistent with the assumption of direct proportionality (log-linear effects) common to most previous research. In contrast, the effects of affluence on CO2 emissions appear to reach a maximum at about $10,000 in per- capita gross domestic product and to decline at higher levels of affluence. These results confirm the general value of the IPAT model as a starting point for understanding the anthropogenic driving forces of global change and suggest that population and economic growth anticipated over the next decade will exacerbate greenhouse gas emissions.

Ion transport and acid-base balance in freshwater bivalves

Blood acid&shy;base and ionic balance in freshwater bivalves is affected by the relative activities of epithelial Na+ and Cl- transporters. In the unionid Carunculina texasensis, the Na+/H+ exchanger is the predominant epithelial transporter that affects acid&shy;base state, while Cl-/HCO3- exchange is of lesser importance. In the corbiculid Corbicula fluminea, Cl- and Na+ transport are both significant components affecting acid&shy;base state. Serotonin (5-hydroxytryptamine, 5-HT) stimulates Na+ and Cl- transport in both species. In C. texasensis, the effect of exogenous serotonin is four times greater on Na+/H+ exchange than on Cl-/HCO3- transport, resulting in an increase in acid secretion and a rise in blood pH. In a Na+-free environment, serotonin had no effect on blood acid&shy;base state in C. texasensis. In C. fluminea, the acid&shy;base consequences of serotonin stimulation of Na+/H+ exchange were offset by similar increases in Cl-/HCO3- exchange and by alterations in blood PCO(sum) in medium containing Na+. In Na+-free medium, stimulation of the Cl- transporter with 5-HT resulted in a decrease in blood pH. The differences between these two species are related to the reliance of C. fluminea on Cl- as the major anion in the blood, requiring high levels of epithelial Cl- transport. In C. texasensis, the anionic component of the blood consists of both Cl- and HCO3- and these ions are interchangeable over a wide concentration range. Extracellular acid&shy;base balance in freshwater bivalves is governed, in part, by epithelial ion transporters.

Potassium transport in the freshwater bivalve Dreissena polymorpha

Potassium transport and blood ion composition were examined in the freshwater bivalve Dreissena polymorpha. Animals acclimated to artificial pondwater (APW, [K+]=0.05 mmol l-1) for 4 weeks gradually lost Na+ and Cl-, but the blood K+ concentration remained constant near 0.5 mmol l-1. Blood [K+] in D. polymorpha declined by 41 % after 1 week of exposure to K+-free APW. Conversely, blood [K+] rose to 1.52&plusmn;0.05 mmol l-1 (mean &plusmn; s.e.m.) 24 h after exposure to 0.5 mmol l-1 K+ APW. Total tissue K+ content remained stable in animals maintained in APW, but fell significantly in animals exposed to K+-free APW for 2 weeks. The net K+ flux (Jnet) for animals incubated in APW, with an average K+ concentration of 0.07 mmol l-1, was -0.27&plusmn;0.06 &micro;equiv g-1 dry tissue h-1, significantly different from the value of 0.50&plusmn;0.08 &micro;equiv g-1 dry tissue h-1 for animals transferred to 0.30 mmol l-1 K+ APW. A transepithelial membrane potential of -3.6&plusmn;0.7 mV (blood negative compared with the bathing medium) was measured in APW-acclimated mussels. Potassium influx was measured with 42K and displayed Michaelis&shy;Menten saturation kinetics at dilute K+ concentrations. The Km was 0.084&plusmn;0.054 mmol l-1 and the Jmax was 1.74&plusmn;0.39 &micro;equiv g-1 dry tissue h-1. Both the Km and Jmax for animals exposed to K+-free APW for 7 days were unchanged. Using 86Rb, qualitatively similar transport characteristics were observed for animals incubated in K+-free, Rb+ APW, but the 22 day K+ depletion time significantly increased Jmax. D. polymorpha compensated for changes in the ionic composition of the acclimation medium by tolerating alterations in blood solute composition and adjusting ion transport rates.

Mechanisms and properties of sodium transport in locust rectum

Steady-state fluxes of 22Na+ were measured as a function of external Na+ concentration across locust recta mounted as flat sheets under short-circuit conditions. A net flux [Formula: see text] at all concentrations confirmed that absorption was an active process obeying Michaelis–Menten kinetics with Kt of 17 mM and Vmax of 1.5 to 2.5 μequiv. cm−2 h−1. [Formula: see text] was not affected by cAMP, was independent of external Cl− levels and stimulated short-circuit current (i.e., Cl− transport), and was partially inhibited by amiloride and ouabain but not by vanadate. Using intracellular electrodes, a small Na+ conductance that was not due to cotransport with organic substrates was identified in the apical plasma membrane. A semiquantitative model for Na+ absorption in this epithelium is proposed. We surveyed the locust neurosecretory system for water-soluble factors that might control rectal Na+ reabsorption.

Thyroid thermogenesis: minimal contribution of energy requirement for protein synthesis

Cycloheximide (5.0 mug/ml) had no significant effect on respiration of liver slices prepared from euthyroid rats (i.e., QO2 of 15.5 +/- 0.8 vs. 14.9 +/- 0.8 mul/mg protein) despite an 83.8 +/- 2.1% inhibition of protein synthesis as judged by [3H]leucine incorporation into the trichloroacetic acid precipitable fraction. Injection of triiodothyronine increased the QO2 of rat liver slices to 22.6 +/- 1.1 mul/h/mg protein. The QO2 of hyperthyroid slices remained high in the presence of cycloheximide although protein synthesis was inhibited by 84.4 +/- 2.0%. These results imply that the energy requirement for protein synthesis contributes little to QO2 of euthyroid liver and does not account for a significant fraction of the increase in hepatic QO2 obtained in the transition from the euthyroid to the hyperthyroid state.