Modular organization of adaptive colouration in flounder and cuttlefish revealed by independent component analysis

Flounders and cuttlefish have an impressive ability to change colouration, for camouflage and, in the case of cuttlefish, for communication. We pursue the hypothesis that these diverse patterns are created by combining a small number of distinct pattern modules. Independent component analysis (ICA) is a powerful tool for identifying independent sources of variation in linear mixtures of signals. Two versions of ICA are used, one assuming that sources have independence over time, and the other over space. These reveal the modularity of the skin colouration system, and suggest how the pattern modules are combined in specific behavioural contexts. ICA may therefore be a useful tool for studying animal camouflage and communication.     

Computed axial tomographic scan measurement of abdominal fat distribution and its correlation with anthropometry and insulin secretion in healthy Asian Indians

Asian Indians have high insulin resistance, hyperinsulinemia, a high prevalence of diabetes, and a high waist to hip ratio (WHR), although the rate of obesity is low. WHR and visceral fat (VF) are highly correlated, and both are associated with insulin resistance. This study was performed to determine the normal ranges of abdominal fat distribution (subcutaneous [SF] and VF) in nondiabetic South Indians and also to study its correlations with WHR, plasma insulin, and metabolic profiles. Fat areas were measured by computed axial tomographic scan at the L4 to L5 level. Mean areas of SF and VF in men and women in this study were similar to the values in white populations. Women had significantly less VF than men. Gender differences were observed in the contribution of fat areas to anthropometric, hormonal, and metabolic variables. In general, in men, total fat (TF) area showed significant independent correlation with body mass index (BMI), WHR, and total cholesterol, and VF correlated with insulin secretion. In women, TF and BMI were correlated and SF showed a correlation with total cholesterol. Insulin secretion in women did not show a correlation with fat areas.     

Tensile behavior of polycrystalline zirconium at 4.2°K

Tensile tests were conducted at 4.2°K on both longitudinal and transverse specimens machined from zirconium plate. In this plate the basal planes of the grains were strongly aligned parallel to and distributed nearly uniformly about the rolling direction. The metal had higher ductility at 4.2°K than at room temperature. Prestraining transverse specimens at 4.2°K produced higher room temperature damping capacity than prestraining at 77°K. All stress-strain curves for the 4.2°K tests exhibited characteristic sudden drops in the load. Transverse specimens showed a much higher incidence of twinning, greater strain hardening, more plastic deformation between serrations, and fewer serrations than longitudinal specimens. The experimental evidence is in agreement with Kula and DeSisto’s conclusions that twinning per se is probably not responsible for the discontinuous yielding. The present observations are also consistent with Basinski’s hypothesis that the load drops are related to thermal softening. A simple calculation shows that at temperatures near absolute zero, the heat generated in a specimen during deformation is much more than that necessary to cause an instability and consequent load drop. Hence it is concluded that all the heat generated is not retained in the specimen and a large fraction must be lost to the surroundings. An estimate of the magnitude of the temperature rise associated with a typical load drop was made.     

Some aspects of the variation of the strain anisotropy in titanium

Strain anisotropy in commercial purity titanium was studied between 77° and 973°K using the technique of Rittenhouse and Picklesimer. Both longitudinal and transverse tensile specimens were used that were machined from a plate with a strong alignment of the basal planes of the grains parallel to the rolling plane. The contractile strain along the transverse plate direction was always larger than that parallel to the rolling plane normal. The strain anisotropy was greatest at the highest temperature. With decreasing temperature it became smaller at an ever increasing rate. At 973°K the strain anisotropy was strain independent. At lower temperatures it decreased with increasing strain. It is believed that deformation twinning can account for most of the temperature and strain dependence of the strain anisotropy. Quantitative microstructure studies show good correspondence between changes in the volume fraction of twins and changes in the strain anisotropy. Transverse specimens exhibited a greater degree of strain anisotropy, and this is consistent with the original texture of the titanium plate used in this investigation.     

An audit of prostate-specific antigen and clinical symptoms in general practice

The objective was to devise local guidelines for the referral of patients with suspected prostatic carcinoma following evaluation by a retrospective audit of the value of the prostate-specific antigen concentration, together with age, urological symptoms, and digital rectal examination in the diagnosis of carcinoma of the prostate. Relevant details were collected from the notes of 582 patients from general practice and hospital. The significant diagnostic factors were ascertained by stepwise logistic regression. Prostate-specific antigen concentration, digital rectal examination and significant terminal dribbling were the most powerful factors in the diagnosis of carcinoma of the prostate. When prostate-specific antigen concentration was considered in isolation, a value of 6.5 ng/ml appeared appropriate for referral. Age was not significant, perhaps due to the narrow patient age range. The significant diagnostic factors were built into an algorithm calculating the probability of carcinoma of the prostate. This algorithm, together with prostate-specific antigen concentration results and digital rectal examination findings, forms the basis of the referral guidelines and a subsequent prospective study.     

Effect of mutating the regulatory phosphoserine and conserved threonine on the activity of the expressed catalytic domain of Acanthamoeba myosin I heavy chain kinase

Phosphorylation of Ser-627 is both necessary and sufficient for full activity of the expressed 35-kDa catalytic domain of myosin I heavy chain kinase (MIHCK). Ser-627 lies in the variable loop between highly conserved residues DFG and APE at a position at which a phosphorylated Ser/Thr also occurs in many other Ser/Thr protein kinases. The variable loop of MIHCK contains two other hydroxyamino acids: Thr-631, which is conserved in almost all Ser/Thr kinases, and Thr-632, which is not conserved. We determined the effects on the kinase activity of the expressed catalytic domain of mutating Ser-627, Thr-631, and Thr-632 individually to Ala, Asp, and Glu. The S627A mutant was substantially less active than wild type (wt), with a lower kcat and higher Km for both peptide substrate and ATP, but was more active than unphosphorylated wt. The S627D and S627E mutants were also less active than phosphorylated wt, i.e., acidic amino acids cannot substitute for phospho-Ser-627. The activity of the T631A mutant was as low as that of the S627A mutant, whereas the T632A mutant was as active as phosphorylated wt, indicating that highly conserved Thr-631, although not phosphorylated, is essential for catalytic activity. Asp and Glu substitutions for Thr-631 and Thr-632 were inhibitory to various degrees. Molecular modeling indicated that Thr-631 can hydrogen bond with conserved residue Asp-591 in the catalytic loop and that similar interactions are possible for other kinases whose activities also are regulated by phosphorylation in the variable loop. Thus, this conserved Thr residue may be essential for the activities of other Ser/Thr protein kinases as well as for the activity of MIHCK.     

Heat Capacity of H2 Adsorbed on Carbon Nanotube Bundles

We report on ongoing measurements of the heat capacity of H₂ adsorbed on closed-end single-wall carbon, nanotube bundles(SWNTB), for 1.5K≤T≤10K and for coverages between 0.04 and 1.4 layers. Coverages are defined from a sharp minimum in heat capacity isotherms. We determine three distinct regions corresponding to: a) Formation of lines of atoms in grooves and large interstitial sites, b) Formation of a layer over the graphite-like outside surface of the bundle, and c) Beginning of growth of the second layer. Resugts are correlated to H₂ vapor pressure isotherms and are compared to helium heat capacity measurements done on the same cell. In, neither ⁴He nor H₂ do we observe a 1-d ideal gas regime.