Minimum vertex distance between separable convex polygons

The minimum vertex distance between two separable convex polygons is found by an optimal algorithm which is linear in the number of vertices.     

Evaluation of the electrostatic effect of the 5'-phosphate of the flavin mononucleotide cofactor on the oxidation--reduction potentials of the flavodoxin from desulfovibrio vulgaris (Hildenborough)

Two mutants of the Desulfovibrio vulgaris flavodoxin, T12H and N14H, were generated which, for the first time, place a basic residue within the normally neutral 5'-phosphate binding loop of the flavin mononucleotide cofactor binding site found in all flavodoxins. These histidine residues were designed to form an ion pair with the dianionic 5'-phosphate, either altering its ionization state or offsetting its negative charge to allow evaluation of the magnitude of its electrostatic effect on the redox properties of the cofactor. The midpoint potential for the oxidized/semiquinone couple was not significantly altered in either mutant. However, the midpoint potentials for the semiquinone/hydroquinone couple (Esq/hq) were less negative than that of the wild type, increasing by 28 and 15 mV relative to that of the wild type for the T12H and N14H mutants, respectively, at pH 6. 31P NMR spectroscopy suggests that, just as for wild type, the phosphate group in each mutant does not change its ionization state between pH 6 and 8. Therefore, the small increases in midpoint potential must be linked to the protonation of the histidine residues, either through favorable interactions with the anionic hydroquinone or by the partial compensation of the charge on the 5'-phosphate. Values for the pKa of His12 and His14 in the oxidized flavodoxin were determined by 1H NMR spectroscopy to be 6.71 and 6.93, respectively, which are only modestly elevated relative to the average value for histidines in proteins. This suggests that the histidines do not form strong ion-pairing interactions with the phosphate and/or that the effective charge on the 5'-phosphate may be substantially less than the reported formal dianionic charge. Either way, the data provide evidence for the rather weak electrostatic interaction between a charged group at this site and the anionic flavin hydroquinone. In contrast, Esq/hq reported for the apoflavodoxin-riboflavin complex, which lacks the 5'-phosphate group, is 180 mV less negative than that of the native flavodoxin. The re-evaluation of the redox and cofactor binding properties of the riboflavin complex generated values for the dissociation constants for the riboflavin complex in the oxidized, semiquinone, and hydroquinone oxidation states that are 2100-, 63000-, and 54-fold higher, respectively, than that for the naturally occurring flavin mononucleotide complex. The large redox potential shifts observed for both redox couples in the riboflavin complex are primarily the consequence of a decreased stabilization of the semiquinone rather than the result of the absence of the negative charge of the 5'-phosphate. It is concluded from this study that the negative charge on the phosphate group of the cofactor does not play a disproportionate role in decreasing Esq/hq, at most contributing equivalently with the acidic amino acid residues clustered around the flavin to an unfavorable electrostatic environment for the formation of the flavin hydroquinone anion.     

Abnormal neurological findings at first admission in patients with schizophrenia or schizophreniform disorders. Results of computer tomography and measurement of regional cerebral blood flow

Forty-five patients with schizophrenia or schizophreniform disorder admitted to hospital for the first time had a neurological examination, including integrative sensory and complex motor acts, by a trained neurologist. The patients were studied by CT and regional cerebral blood flow as well. A control group of 24 healthy volunteers was included. The patients had significantly more neurological abnormalities (NA) than the healthy volunteers. Medication did not explain the discrepancy. The NA were associated with sulcal enlargement and smaller brains as visualized by CT but not with ventricular enlargement. There was no association between the regional flow values and NA.     

Repeated bile acid therapy for the long-term management of cholesterol gallstones

BACKGROUND/AIMS: Following non-surgical treatment, cholesterol gallstones recur in a high proportion of patients, and recurrence cannot be predicted nor effectively prevented. Our aim was to test prospectively the viability and the efficacy of repeated bile acid therapy, in which recurrent stones are diagnosed at an early stage by regular ultrasound monitoring and promptly retreated, as a strategy for the management of these patients in clinical practice. METHODS: One hundred and seventy-two consecutive patients were recruited upon achieving complete gallstone dissolution using non-surgical therapy (bile acids or lithotripsy plus bile acids), and followed up at 6-monthly intervals by ultrasound scan. Gallstone recurrence was promptly treated by a combination of ursodeoxycholic acid plus chenodeoxycholic acid (5 mg/kg per day each) for a period of 2 years, or less if complete redissolution was achieved. Median follow-up period was 34 months (range 6-70). RESULTS: Forty-five patients had gallstone recurrence; of these, 39 underwent one or more repeated courses of bile acid therapy (follow-up data available in 27). Gallstone recurrence rate was 15% at 1 year and 47% at 5 years. Average annual redissolution rate of recurrent gallstones (intention to treat) was 41%. The proportion of gallstone-free patients in the whole population was 88%, 84%, 77%, 78%, 75% at 1-5 years, respectively, and rose to > 90% at 3 years onwards in patients with single primary stones. CONCLUSIONS: We conclude that repeated bile acid therapy maintains the majority of patients gallstone free, and is therefore an effective long-term management strategy, especially in patients with primary single gallstones.     

Effects of growth rate on carcass composition and lipid partitioning at puberty and growth hormone, insulin-like growth factor I, insulin, and metabolites before puberty in beef heifers

The effect of three rates of gain on carcass composition, lipid partitioning, age and BW at puberty, and concentrations of growth hormone (GH), IGF-I, insulin, glucose, and NEFA in plasma were evaluated in 38 Angus x Hereford heifers. Heifers were allotted by BW and age to three treatments with a replication in each of 2 yr: full-fed (n = 13; FF) to gain 1.36 kg/d; limit-fed (n = 12; LF) to gain .68 kg/d; maintenance-full-fed (n = 13; MFF) to gain .23 kg/d for 16 wk, then full-fed to gain 1.36 kg/d. Heifers were slaughtered within 10 d after the onset of puberty. At slaughter, kidney, pelvic, and heart fat (KPH) and udder (UDDER) were separated from carcass, as was fat surrounding viscera (OM). After 48 h at 4 degrees C a carcass side was dissected into subcutaneous fat (SC), intermuscular fat (SEAM), soft tissue (SFT = inseparable lean and fat), LEAN, and BONE. In yr 1, LF heifers (431 d) were older (P < .05) than MFF heifers (371 d) at puberty, but age of FF heifers (389 d) did not differ (P > .10) from that of LF and MFF heifers. In yr 2, FF heifers (351 d) were younger (P < .05) than LF and MFF heifers (398 and 434 d, respectively). The FF heifers had greater (P < .05) BW and a greater (P < .01) percentage of lipid in the carcass at puberty than LF and MFF heifers. During the first 16 wk of treatment, concentrations of NEFA were greater in heifers with slower daily gains (MFF > LF > FF; P < .01). Concentrations of NEFA were lesser and concentrations of IGF-I and insulin were greater in plasma of FF than in that of MFF heifers during the 10 wk before puberty. Treatment significantly altered age, BW, carcass composition, and lipid partitioning at puberty in beef heifers. We conclude that the percentage of body fat is not the sole regulator of puberty, and age may be an important modulator in determining the onset of puberty in beef heifers.     

Symbolic time-series analysis for anomaly detection in mechanical systems

This paper examines the efficacy of a novel method for anomaly detection in mechanical systems, which makes use of a hidden Markov model, derived from the time-series data of pertinent measurement(s). The core concept of the anomaly detection method is symbolic time-series analysis that is built upon the principles of Automata Theory, Information Theory, and Pattern Recognition. The performance of this method is compared with that of other existing pattern-recognition techniques from the perspective of early detection of small fatigue cracks in ductile alloy structures. The experimental apparatus, on which the anomaly detection method is tested, is a multi-degree-of-freedom mass-beam structure excited by oscillatory motion of two electromagnetic shakers. The evolution of fatigue crack damage at one or more failure sites are detected from symbolic time-series analysis of displacement sensor signals.     

Nitroprusside suppresses cochlear potentials and outer hair cell responses

Biochemical and pharmacological evidence supports a role for nitric oxide (NO) in the cochlea. In the present experiments, we tested sodium nitroprusside (SNP), an NO donor, applied by intracochlear perfusions on sound-evoked responses of the cochlea (CM, cochlear microphonic; SP, summating potential; EP, endocochlear potential; CAP, compound action potential) and in vitro on outer hair cell (OHC) voltage-induced length changes and current responses. In vivo application of SNP in increasing concentrations (10, 33, 100, 330 and 1000 microM) reduced all sound-evoked responses starting at about 300 microM. The responses continued to decline after a postdrug wash. At 1 mM SNP decreased EP slowly (approximately 80 min) whereas at 10 mM it reduced EP more rapidly (approximately 20 min). Ferricyanide (1 mM) and S-nitroso-N-acetylpenicillamine (SNAP; 1 mM) had no effect on sound-evoked cochlear potentials. Ferricyanide (1 mM and 10 mM) and ferrocyanide (10 mM) had no effect on EP. In vitro, SNP (10 mM) significantly reduced both OHC voltage-induced length changes and whole-cell outward currents. Results suggest that SNP, possibly acting by released NO, influences cochlear function through effects at the stria vascularis and at the OHCs.     

Screw-theoretic analysis framework for cooperative payload transport by mobile manipulator collectives

In recent times, there has been considerable interest in creating and deploying modular cooperating collectives of robots. Interest in such cooperative systems typically arises when certain tasks are either too complex to be performed by a single agent or when there are distinct benefits that accrue by cooperation of many simple robotic modules. However, the nature of both the individual modules as well as their interactions can affect the overall system performance. In this paper, we examine this aspect in the context of cooperative payload transport by robot collectives wherein the physical nature of the interactions between the various modules creates a tight coupling within the system. We leverage the rich theoretical background of analysis of constrained mechanical systems to provide a systematic framework for formulation and evaluation of system-level performance on the basis of the individual-module characteristics. The composite multi-degree-of-freedom (DOF) wheeled vehicle, formed by supporting a common payload on the end-effectors of multiple individual mobile manipulator modules, is treated as an in-parallel system with articulated serial-chain arms. The system-level model, constructed from the twist- and wrench-based models of the attached serial chains, can then be systematically analyzed for performance (in terms of mobility and disturbance rejection). A two-module composite system example is used throughout the paper to highlight various aspects of methodical system model formulation, effects of selection of active, passive or locked articulations on system performance, and experimental validation on a hardware prototype test bed.