The role of user preference in the customized control of robotic exoskeletons.

User preference is a promising objective for the control of robotic exoskeletons because it may capture the multifactorial nature of exoskeleton use. However, to use it, we must first understand its characteristics in the context of exoskeleton control. Here, we systematically measured the control preferences of individuals wearing bilateral ankle exoskeletons during walking. We investigated users' repeatability identifying their preferences and how preference changes with walking speed, device exposure, and between individuals with different technical backgrounds. Twelve naive and 12 knowledgeable nondisabled participants identified their preferred assistance in repeated trials by simultaneously self-tuning the magnitude and timing of peak torque. They were blinded to the control parameters and relied solely on their perception of the assistance to guide their tuning. We found that participants' preferences ranged from 7.9 to 19.4 newton-meters and 54.1 to 59.2 percent of the gait cycle. Across trials, participants repeatably identified their preferences with a mean standard deviation of 1.7 newton-meters and 1.5 percent of the gait cycle. Within a trial, participants converged on their preference in 105 seconds. As the experiment progressed, naive users preferred higher torque magnitude. At faster walking speeds, these individuals were more precise at identifying the magnitude of their preferred assistance. Knowledgeable users preferred higher torque than naive users. These results highlight that although preference is a dynamic quantity, individuals can reliably identify their preferences. This work motivates strategies for the control of lower limb exoskeletons in which individuals customize assistance according to their unique preferences and provides meaningful insight into how users interact with exoskeletons.

The Red Kangaroo pericardium as a material source for the manufacture of percutaneous heart valves.

BACKGROUND: The kangaroo pericardium might be considered to be a good candidate material for use in the manufacture of the leaflets of percutaneous heart valves based upon the unique lifestyle. The diet consists of herbs, forbs and strubs. The kangaroo pericardium holds an undulated structure of collagen. MATERIAL AND METHOD: A Red Kangaroo was obtained after a traffic fatality and the pericardium was dissected. Four compasses were cut from four different sites: auricular (AUR), atrial (ATR), sternoperitoneal (SPL) and phrenopericardial (PPL). They were investigated by means of scanning electron microscopy, light microscopy and transmission electron microscopy. RESULTS: All the samples showed dense and wavy collagen bundles without vascularisation from both the epicardium and the parietal pericardium. The AUR and the ATR were 150±25µm thick whereas the SPL and the PPL were thinner at 120±20µm. The surface of the epicardium was smooth and glistening. The filaments of collagen were well individualized without any aggregation, but the banding was poorly defined and somewhat blurry. CONCLUSION: This detailed morphological analysis of the kangaroo pericardium illustrated a surface resistant to thrombosis and physical characteristics resistant to fatigue. The morphological characteristics of the kangaroo pericardium indicate that it represents an outstanding alternative to the current sources e.g., bovine and porcine. However, procurement of tissues from the wild raises supply and sanitary issues. Health concerns based upon sanitary uncertainty and reliability of supply of wild animals remain real problems.

Low-abundance HIV species and their impact on mutational profiles in patients with virological failure on once-daily abacavir/lamivudine/zidovudine and tenofovir.

BACKGROUND: HIV clonal genotypic analysis (CG) was used to investigate whether a more sensitive analysis method would detect additional low-abundance mutations compared with population genotyping (PG) in antiretroviral-naive patients who experienced virological failure (VF) during treatment with abacavir/lamivudine/zidovudine and tenofovir. METHODS: HIV was analysed by PG and CG (771 baseline and 657 VF clones) from subjects with VF (confirmed HIV RNA > or = 400 copies/mL at 24-48 weeks). RESULTS: Fourteen of 123 subjects (11%) met VF criteria; their median baseline HIV RNA was 5.4 log(10) copies/mL, and 4.0 log(10) copies/mL at VF. By baseline PG, 2/14 had HIV-1 with nucleoside reverse transcriptase inhibitor (NRTI) or non-NRTI mutations. By baseline CG, 9/14 had HIV-1 with NNRTI and/or NRTI mutations; 7/9 had study drug-associated mutations. By PG at VF, 10/14 had selected for resistance mutations [2, K65R; 1, M184V; and 7, thymidine analogue mutations (TAMs) +/- M184V]. By CG at VF, for subjects with TAMs, T215F was more commonly detected (5/14 samples) than T215Y (2/14). For one subject who selected K65R at VF, both K65R-containing clones and TAM-containing clones (both T215A and T215F) were observed independently but not conjunctively in the same clone in a post-VF sample. CONCLUSIONS: The majority of subjects with VF had major and minor mutations detected at VF; CG detected additional low-abundance variants at baseline and VF that could have influenced mutation selection pathways. Both PG and CG data suggest TAMs, not K65R selection, are the preferred resistance route, biased towards 215F selection. No HIV clone contained both K65R and T215F/Y mutations, suggesting in vivo antagonism between the two mutations. The once-daily zidovudine usage and high baseline viraemia may also have contributed to rapid selection of HIV with multiple mutations in VFs.

The timing of histologic changes in liver lacerations.

Microscopic examination was performed on 55 cases of traumatic liver lacerations incurred from fatal motor vehicle accidents. None of the deaths was due to the liver injury. In 38 of 55 cases, the decedent was pronounced dead at the scene. Microscopic examination of the liver lacerations in these 38 cases revealed no histologic changes related to the trauma. In 17 of 55 cases, the decedent was transported to the emergency room (ER) with a "survival time" (from Emergency Medical Service arrival to the time of pronouncement) of 15 minutes to 7 hours and 10 minutes. Nine of these 17 had vital signs at the scene. Five of the 17 had neutrophilic infiltration and hepatocyte necrosis at the site of the laceration. Four of these had vitals signs at the scene. Survival time of the 5 patients with a vital reaction at their liver injury ranged from 51 minutes to 7 hours and 10 minutes.

Vinyl carbocations: solution studies of alkenyl(aryl)iodonium triflate fragmentations.

Generation of vinyl cations is facile by fragmentation of alkenyl(aryl)iodonium trifluoromethanesulfonates. Kinetics and electronic effects were probed by (1)H NMR spectroscopy in CDCl(3). Products of fragmentation include six enol triflate isomers in addition to iodoarenes. The enol triflates arise from direct reaction of a triflate anion with the starting iodonium salts as well as triflate reaction with rearranged secondary cations derived from those salts. G2 calculations of the theoretical isodesmic hydride-transfer reaction between secondary vinyl cation 7 and primary vinyl cation 6 reveal that cation 6 is 17.8 kcal/mol higher in energy. Activation parameters for fragmentation of (Z)-2-ethyl-1-hexenyl(3,5-bis-trifluoromethylphenyl)iodonium triflate, 17e, were calculated using the Arrhenius equation: E(a) = 26.8 kcal/mol, Delta H(++) = 26.2 kcal/mol, and Delta S(++) = 11.9 cal/mol x K. Added triflate increases the rate of fragmentation slightly, and it is likely that for most beta,beta-dialkyl- substituted vinylic iodonium triflates enol triflate fragmentation products are derived from three competing mechanisms: (a) vinylic S(N)()2 substitution; (b) ligand coupling (LC); and (c) concerted aryliodonio departure and 1,2-alkyl shift leading to secondary rather than primary vinyl cations.

The role of Clostridium septicum in paraneoplastic sepsis.

CONTEXT: Clostridium septicum infections are rare but often associated with serious if not fatal outcomes. Clostridium septicum infection does not appear to be associated with a single specific defect in cellular or humoral immunity. It has been associated with multiple medical problems, including but not limited to leukemia, malignancy of the bowel, other solid tumors, cyclic neutropenia with enterocolitis, diabetes mellitus, and severe arteriosclerosis. Most cases of C septicum are associated with malignancy, and mortality approaches 100% if care is not rendered within 12 to 24 hours. OBJECTIVES: To evaluate outcomes of patients with C septicum bacteremia, whether treated medically or surgically or both, and to note associated conditions. DESIGN: Retrospective evaluation of patients found to have C septicum bacteremia in the past 6 years. SETTING: Two teaching hospitals, Brooke Army Medical Center (250 beds) and Wilford Hall Medical Center (292 beds), were the source of our patients. PATIENTS: All patients found to have C septicum bacteremia during hospitalization or postmortem examination were included in the study. There were no exclusion criteria. MAIN OUTCOME MEASURE: Mortality associated with C septicum infection. RESULTS: In our case series, mortality was 33%, which is slightly lower than reported in prior studies (43%-70%). CONCLUSION: Presumptive identification based on Gram stain, awareness of C septicum infection as a paraneoplastic syndrome, and prompt, clear communication between laboratory personnel and clinicians are necessary for early diagnosis of C septicum infection. Early institution of antibiotic therapy improves prognosis.

A descriptive evaluation with follow-up of the clinical significance of atypical immature squamous metaplasia of the cervix.

OBJECTIVES: We set out to determine the clinical significance of atypical immature squamous metaplasia (AIM). METHODS: We performed in a military, hospital-based colposcopy clinic a descriptive, retrospective review of patients who had a diagnosis of AIM. Patients were examined at 3- to 4-month intervals for at least 1 year after a diagnosis of AIM was established. A gynecological pathologist reviewed all histological and cytological specimens. Initial histological or cytological specimens were tested for the presence of HPV DNA using in situ hybridization. RESULTS: High-risk HPV DNA types 16 or 18 were detected in 3% of patients with AIM. Concurrent cervical intraepithelial neoplasia 3 (CIN3) was noted in 3% of patients with AIM. One-third of patients with initially diagnosed AIM had complete resolution of this lesion after 1 year of follow-up. CONCLUSIONS: This descriptive, retrospective review shows that AIM does not appear to be associated with high-risk HPV DNA or with CIN3. In this limited study, a concurrent diagnosis of AIM likely does not influence the 1-year behavior of CIN. The degree of CIN should dictate treatment recommendations. A larger prospective trial is needed.

Propofol anaesthesia in electroconvulsive therapy. Reduced seizure duration may not be relevant.

BACKGROUND: The induction agent propofol is known to reduce electroconvulsive therapy (ECT) seizure duration. It is assumed that outcome from depression is adversely affected by this agent. This study compares propofol and methohexitone as induction agents for ECT. METHOD: In a prospective, randomised, double-blind study 20 subjects with major depressive disorder (DSM-III-R criteria) received propofol or methohexitone anaesthesia. The Hamilton Depression Rating Scale and Beck Depression Inventory were used to assess depression before therapy, at every third treatment, and at the end of therapy. Seizure duration was measured using the cuff technique. RESULTS: Mean seizure durations (P < 0.01) and mean total seizure duration (P < 0.01) were shorter in the propofol group. There was no difference in outcome. CONCLUSIONS: Use of propofol may not adversely affect outcome from depression and it is not necessarily contraindicated as an induction agent for ECT. Our results should be interpreted cautiously, and larger studies are needed.

Propofol for electroconvulsive therapy. A comparison with methohexitone. Preliminary report.

Twenty patients who received electroconvulsive therapy were anaesthetised with either propofol or methohexitone in a randomised crossover study. Recovery times were similar but patients who received propofol tended to be orientated sooner. The decrease in arterial blood pressure after induction was greater with propofol than with methohexitone. There was an increase in blood pressure immediately after therapy in patients who received methohexitone but not in those given propofol. There was a slight difference in pain on injection. The mean duration of convulsion (measured in 10 patients) during anaesthesia was shorter with propofol than with methohexitone.

Spectroscopic characterization of cardiovascular tissue.

We present results of a series of laser spectroscopic measurements on in vitro samples of cardiovascular tissue. These include laser Raman scattering, Fourier transform infrared, plasma emission and fluorescence, and electron paramagnetic resonance spectroscopy. The results of these spectroscopic measurements are discussed in terms of their implications for the field of laser angioplasty.

An unusual type of keratopathy observed in polyurethane workers and its reproduction in experimental animals.

We have reported two cases of keratopathy in polyurethane workers that appear to be identical to those described by previous authors. We have been able to produce similar findings in the corneas of cats by exposing the eyes of anesthetized animals to the vapor of two of the amines used as catalysts in polyurethane manufacture. We were unable to reproduce these results with toluene diisocyanate. Therefore we support the previous suggestion that the amine catalysts are responsible for the distinctive keratopathy in polyurethane workers. We are unable to substantiate the claim that toluene diisocyanate is responsible for this phenomenon.

Influence of aspirin and indomethacin on variability of alveolar hypoxic vasoconstriction.

Alveolar hypoxia induces pulmonary vasoconstriction but the strength of alveolar hypoxic vasoconstriction (AHV) is variable even within the same species. The influence of aspirin and indomethacin, cyclo-oxygenase inhibitors, was examined in two groups of dogs, those with weak AHV and those with vigorous AHV. A double-lumen endotracheal tube allowed ventilation of one lung with nitrogen as an alveolar hypoxic stimulus and ventilation of the other lung with O2 to maintain systemic oxygenation. Perfusion to each lung was measured with xenon-133 and external counters. In weak reactors both aspirin and indomethacin induced fourfold enhancement of AHV (P less than 0.01), whereas no significant influence on vigorous reactors was noted. Cyclo-oxygenase inhibitors also produced enhanced reactivity in the isolated lung to alveolar hypoxia and prostaglandin F2alpha but not to angiotensin II and norepinephrine. Aspirin-enhanced AHV in the isolated lung could not be diminished with blockade of angiotensin II receptors or of alpha receptors. In summary, weak AHV in intact or isolated dog lung may be due to an excess of a prostaglandin or prostacyclin vasodilator.

Failure of saralasin acetate, a competitive inhibitor of angiotensin II, to diminish alveolar hypoxic vasoconstriction in the dog.

The role of angiotensin II in the pulmonary vasoconstriction induced by alveolar hypoxia was investigated with the competitive inhibitor of angiotensin, saralasin acetate. Unilateral alveolar hypoxia was induced in dogs by ventilation of one lung with 100% N2 through a double lumened endotracheal cannula while maintaining adequate systemic oxygenation by ventilating the other lung with 1oo% O2. Pulmonary perfusion was monitored with 133Xe and external detectors. In 8 dogs perfusion to the test lung on room air before N2 ventilation was 49.2% (SEM +/- 3.8) of total lung perfusion. After 7 min of nitrogen ventilation, perfusion to that lung was 35.6% (SEM +/- 2.9) of cardiac output (P less than 0.001), a reduction of 27.5% (SEM +/- 2.4). After infusion of 6--24 microgram.kg-1/min of saralasin acetate, beginning 2 min before the alveolar hypoxic challenge and continuing through it, unilateral alveolar hypoxia continued to reduce perfusion to that lung by 28.8% (P = 0.6 from control). In 2 dogs a higher infusion of 60 microgram.kg-1/min failed to reduce the alveolar hypoxic vasoconstriction and in 2 dogs a 15 min infusion of 6 microgram.kg-1 of saralasin acetate before alveolar hypoxia and continuing through it, still failed to inhibit alveolar hypoxic vasoconstriction. Thus, no role was demonstrated for angiotensin II in acute alveolar hypoxic vasoconstriction of the dog.

Role of prostaglandins in alveolar hypoxic vasoconstriction.

The role of prostaglandins as mediators of alveolar hypoxic vasoconstriction was investigated in dogs with the use of the prostaglandin synthesis inhibitors, aspirin and indomethacin. Alveolar hypoxia was induced by inserting double-lumened endotracheal tube into the carina and ventilating one lung with nigrogen while maintaining normal systemic oxygenation with 100% O(2) ventilation to the other lung. Relative perfusion to each lung was determined with 133Xenon and external counters. Infusions up to 25 mg/kg of indomethacin and up to 250 mg/kg of aspirin did not block the shift in perfusion from the alveolar hypoxic lung. In fact, the shift in perfusion from the alveolar hypoxic lung was slightly augmented by aspirin (P = 0.03). Thus, no positive role was demonstrated in the dog for prostaglandins in producing the vasoconstriction of alveolar hypoxia.