Localization and physical property experiments conducted by Opportunity at Meridiani Planum

The location of the Opportunity landing site was determined to better than 10-m absolute accuracy from analyses of radio tracking data. We determined Rover locations during traverses with an error as small as several centimeters using engineering telemetry and overlapping images. Topographic profiles generated from rover data show that the plains are very smooth from meter- to centimeter-length scales, consistent with analyses of orbital observations. Solar cell output decreased because of the deposition of airborne dust on the panels. The lack of dust-covered surfaces on Meridiani Planum indicates that high velocity winds must remove this material on a continuing basis. The low mechanical strength of the evaporitic rocks as determined from grinding experiments, and the abundance of coarse-grained surface particles argue for differential erosion of Meridiani Planum.

Pancam multispectral imaging results from the Opportunity Rover at Meridiani Planum

Panoramic Camera (Pancam) images from Meridiani Planum reveal a low-albedo, generally flat, and relatively rock-free surface. Within and around impact craters and fractures, laminated outcrop rocks with higher albedo are observed. Fine-grained materials include dark sand, bright ferric iron-rich dust, angular rock clasts, and millimeter-size spheroidal granules that are eroding out of the laminated rocks. Spectra of sand, clasts, and one dark plains rock are consistent with mafic silicates such as pyroxene and olivine. Spectra of both the spherules and the laminated outcrop materials indicate the presence of crystalline ferric oxides or oxyhydroxides. Atmospheric observations show a steady decline in dust opacity during the mission. Astronomical observations captured solar transits by Phobos and Deimos and time-lapse observations of sunsets.

Localization and physical properties experiments conducted by Spirit at Gusev Crater

The precise location and relative elevation of Spirit during its traverses from the Columbia Memorial station to Bonneville crater were determined with bundle-adjusted retrievals from rover wheel turns, suspension and tilt angles, and overlapping images. Physical properties experiments show a decrease of 0.2% per Mars solar day in solar cell output resulting from deposition of airborne dust, cohesive soil-like deposits in plains and hollows, bright and dark rock coatings, and relatively weak volcanic rocks of basaltic composition. Volcanic, impact, aeolian, and water-related processes produced the encountered landforms and materials.

Pancam multispectral imaging results from the Spirit Rover at Gusev Crater

Panoramic Camera images at Gusev crater reveal a rock-strewn surface interspersed with high- to moderate-albedo fine-grained deposits occurring in part as drifts or in small circular swales or hollows. Optically thick coatings of fine-grained ferric iron-rich dust dominate most bright soil and rock surfaces. Spectra of some darker rock surfaces and rock regions exposed by brushing or grinding show near-infrared spectral signatures consistent with the presence of mafic silicates such as pyroxene or olivine. Atmospheric observations show a steady decline in dust opacity during the mission, and astronomical observations captured solar transits by the martian moons, Phobos and Deimos, as well as a view of Earth from the martian surface.

Wind-related processes detected by the Spirit Rover at Gusev Crater, Mars

Wind-abraded rocks, ripples, drifts, and other deposits of windblown sediments are seen at the Columbia Memorial Station where the Spirit rover landed. Orientations of these features suggest formative winds from the north-northwest, consistent with predictions from atmospheric models of afternoon winds in Gusev Crater. Cuttings from the rover Rock Abrasion Tool are asymmetrically distributed toward the south-southeast, suggesting active winds from the north-northwest at the time (midday) of the abrasion operations. Characteristics of some rocks, such as a two-toned appearance, suggest that they were possibly buried and exhumed on the order of 5 to 60 centimeters by wind deflation, depending on location.

Pancam multispectral imaging results from the Spirit Rover at Gusev Crater

Panoramic Camera images at Gusev crater reveal a rock-strewn surface interspersed with high- to moderate-albedo fine-grained deposits occurring in part as drifts or in small circular swales or hollows. Optically thick coatings of fine-grained ferric iron-rich dust dominate most bright soil and rock surfaces. Spectra of some darker rock surfaces and rock regions exposed by brushing or grinding show near-infrared spectral signatures consistent with the presence of mafic silicates such as pyroxene or olivine. Atmospheric observations show a steady decline in dust opacity during the mission, and astronomical observations captured solar transits by the martian moons, Phobos and Deimos, as well as a view of Earth from the martian surface.

Psychotropic substance-seeking: evolutionary pathology or adaptation?

According to a conventional evolutionary perspective, the human propensity for substance use is the product of a 'mismatch' between emotional mechanisms that evolved in a past without pure drugs or direct routes of drug administration, and the occurrence of these phenomena in the contemporary environment. The primary purpose of this review is to assert that, contrary to the conventional view, humans have shared a coevolutionary relationship with psychotropic plant substances that is millions of years old. We argue that this 'deep time' relationship is self-evident both in the extant chemical-ecological adaptations that have evolved in mammals to metabolize psychotropic plant substances and in the structure of plant defensive chemicals that have evolved to mimic the structure, and interfere with the function, of mammalian neurotransmitters. Given this evidence, we question how emotional mechanisms easily triggered by plant toxins can have evolved. Our argument is also supported with archeological and historical evidence of substance use in antiquity suggesting that, for people in the past, psychotropic plant substances were as much a mundane everyday item as they are for many people today. Our second, and more speculative objective is to suggest provisional hypotheses of human substance-using phenomena that can incorporate the evolutionary implications of a deep time relationship between psychotropic substances and people. We discuss hypotheses of selective benefits of substance use, including the idea that neurotransmitter-analog plant chemicals were exploited as substitutes for costly, nutritionally constrained endogenous neurotransmitters. However, even if substance seeking was adaptive in the environment of our hominid ancestors, it may not still be so in the contemporary environment. Thus, the implications of our argument are not that the mismatch concept does not apply to human substance-using phenomena, but that it must be reconsidered and extended to incorporate the implications of a substance-rich, rather than substance-free, evolutionary past.

Augmented feedback reduces jump landing forces

STUDY DESIGN

Randomized, experimental design using a 1-way ANCOVA to determine the influence of various forms of feedback on jump landing forces.

OBJECTIVE

To investigate the effects of augmented feedback versus sensory feedback on the reduction of jump landing forces.

BACKGROUND

Several investigators have reported an increased risk of lower extremity injury associated with landing from a jump.

METHODS AND MEASURES

Nonimpaired college students (N=63) were randomly assigned to 1 of 4 feedback groups. Subjects were instructed to perform maximal vertical jumps onto a force plate for 3 testing sessions (baseline, 2-minute post-test, and 1-week post-test). Three feedback groups (augmented, sensory, and control I) were tested during all 3 testing sessions, while a fourth feedback group (control II) was evaluated at only 2 sessions (baseline and 1-week post-test). Subjects in the augmented feedback condition were provided information via video and verbal analysis of how to land softer. Subjects in the sensory feedback condition were asked to use the experience of their baseline jumps to document how they could land softer. Subjects in each of the control groups were not provided any extraneous feedback. Peak vertical ground reaction force data were collected for analysis.

RESULTS

The subjects in the augmented feedback group significantly reduced their peak vertical ground reaction force in both post-test conditions (2-minute post-test reduction, 0.85+/-0.62; 1-week post-test reduction, 0.74+/-0.58) as compared to the sensory, control I, and control II feedback groups.

CONCLUSIONS

High impact landing forces may be reduced by the implementation of augmented feedback information instructing individuals about how to land properly. The reduction of jump landing forces with the use of augmented feedback may prove beneficial in the creation of instructional landing programs.

Truth-telling and patient diagnoses

How do physicians handle informing patients of their diagnoses and how much information do patients really want? How do registered nurses view both sides of this question? Three questionnaires were constructed and administered in a mid-size hospital in New York state. Physicians and nurses underestimate the number of patients who want detailed information. Patients who earn more than average, have a college education, and who are under age 60 are more likely to want information, and state that their physician should give it to them. Only 42% of physicians state that patients want a detailed description of their diagnosis and treatment options. Physicians educated outside the USA appeared to be more likely to change their criteria for informing patients and, along with American-educated nurses, were more willing to participate in formal discussions of the issue. Physicians should comply with the wishes of patients for information and include them in the team deciding on diagnosis and treatment.

When does the flat-top talus lesion occur in idiopathic clubfoot: evaluation with magnetic resonance imaging at three months of age

Flat-top talus has been described as a pathologic change secondary to idiopathic clubfoot condition and/or as a direct result of nonoperative manipulation involving forced dorsiflexion and molding of the cartilaginous talus. No definitive study, however, on the etiology and the timing of the flat-top talus deformity has been performed to date. The authors evaluated the magnetic resonance images of eleven patients with idiopathic clubfoot deformities treated with 2 to 3 months of casting to assess if flattening of the talar dome occurred at this age with this amount of casting. All children were 3 months of age, were casted for a maximum of 2 to 3 months, and sedated before MRI examination. The images were evaluated for maximum talar head height, maximum talar body height, and deviation of the talar body from a perfect circle. Maximum talar head height ranged from 4 to 9 mm, maximum talar body height ranged from 6 to 10 mm. Eight of the eleven had maximum talar body measurements 3 to 5mm greater than maximum talar head height. Three of the eleven patients had head and body size of equal proportion. Two of the eleven had a talar body that was within 1 mm of a perfect circle. The remaining nine patients had perfectly round talar bodies. In the senior author's (RSD) experience with treating clubfeet, a substantial increase has been seen at operation in flat-top tali among children that were casted for more than 1 year before surgical correction, compared to children casted for 3 months before surgical correction. The current investigation indicated that although tali of children with clubfeet are abnormally shaped, the talar body remains larger than the talar head and maintains its roundness after two to three months of corrective casting. Maintenance of cast treatment for more than three months may lead to the flat-top talus deformity. The authors recommend surgical intervention following three months of failed manipulation and casting to prevent this deformity.

Development of an enhanced anticaries efficacy dual component dentifrice containing sodium fluoride and dicalcium phosphate dihydrate

A dual-chamber dentifrice, which contains sodium fluoride (NaF) in one component and dicalcium phosphate dihydrate (dical) in the other, has been developed. The dentifrice is packaged in a dual-chamber tube and is formulated to deliver 1100 ppm F. A series of studies consisting of in vitro fluoride uptake, in vivo calcium labeling, intraoral remineralization-demineralization, and animal caries studies were performed to support the improved anticaries efficacy of this product in comparison to a sodium fluoride/silica dentifrice (NaF/silica). An in vitro fluoride uptake study comparing 1100 ppm F NaF/dical dentifrice to 1100 ppm F NaF/silica showed that NaF/dical delivered significantly more fluoride than NaF/silica, 3.72 +/- 0.36 micrograms/cm2 versus 2.41 +/- 0.10 micrograms/cm2. A 6-day in vivo brushing study with a 44Ca labeled NaF/dical dentifrice showed that calcium from dical penetrated demineralized enamel and was present in plaque up to 18 hrs since the last brushing. An intra-oral remineralization-demineralization study was performed to evaluate NaF/dical's ability to promote remineralization in comparison to three silica-based dentifrices containing 0, 250, and 1100 ppm F as NaF. The percent mineral changes after treatment were +20.44 +/- 17.14 for NaF/dical, +9.27 +/- 19.53 for 1100 ppm NaF/silica, -1.43 +/- 20.57 for 250 ppm NaF/silica, and -12.36 +/- 32.76 for 0 ppm F/silica. A statistical analysis showed that the dual-chamber NaF/dical dentifrice was significantly more effective than the 1100 ppm NaF/silica dentifrice at promoting remineralization. A rat caries study was performed to evaluate NaF/dical ability to prevent caries in comparison to 1100 ppm F NaF/silica, 250 ppm F NaF/silica, silica, and dical dentifrices. The mean smooth surface caries scores were 1.6 +/- 2.8 for NaF/dical, 5.5 +/- 6.2 for 1100 ppm F NaF/silica, 10.6 +/- 6.2 for 250 ppm F NaF/silica, 13.7 +/- 4.7 for 0 ppm F/silica, and 9.5 +/- 7.8 0 ppm F/dical. A statistical analysis showed that the the dual-chamber NaF/dical dentifrice was superior to all other treatments tested in preventing caries in rats. The dical dentifrice was significantly superior to the silica dentifrice in preventing caries, which indicates that dical alone exhibits anticaries efficacy. In conclusion, individual and cumulative results from the fluoride uptake, intra-oral remineralization-demineralization, and rat caries studies from the dual chamber NaF/dical dentifrice support the improved anticaries efficacy of this product.

Biomechanical evaluation of calcaneocuboid distraction arthrodesis: a cadaver study of two different fixation methods

Calcaneocuboid distraction arthrodesis can be used to treat stage 2 posterior tibial tendon dysfunction. Nonunion, graft resorption, and implant failure have been reported after this procedure. This study compared two of the most commonly used methods for fixation of calcaneocuboid distraction arthrodesis. Twelve pairs of cadaver feet underwent simulated calcaneocuboid distraction arthrodesis. One specimen in each pair was fixed with two crossed 3.5 mm cortical lag screws. The contralateral specimen was fixed with a cervical H-plate. The calcaneus was fixed and a load was applied to the plantar aspect of the cuboid at a rate of 5 mm/minute until joint separation of 3 mm or fracture occurred. The average applied load to failure at 1.0 mm of joint separation was 30.5 +/- 11.6 N for the crossed screws and 77.7 +/- 36.4 N for the cervical H-plate (p = 0.001). The average stiffness at 1.0 mm of joint separation was 27.5 +/- 10.9 N/mm for the crossed screws and 43 +/- 21.2 N/mm for the cervical H-plate (p = 0.036). The higher stiffness and load to failure may account for the decreased nonunion rate noted anecdotally by some surgeons with H-plate fixation over crossed screw fixation for calcaneocuboid distraction arthrodesis.

Effects of chewing betel nut (Areca catechu) on the symptoms of people with schizophrenia in Palau, Micronesia

BACKGROUND

Although millions of people with schizophrenia live in betel chewing regions, the effects of betel chewing on their symptoms are unknown. Betel nut alkaloids include potent muscarinic cholinomimetics: recent research suggests that these agents may be therapeutic in schizophrenia.

AIMS

To compare the primary and extrapyramidal symptom profiles and substance-using habits of betel chewing v. non-chewing people with schizophrenia.

METHOD

A cross-sectional study of 70 people with schizophrenia. Symptom ratings measured by the Positive and Negative Syndrome Scale (PANSS) and Extrapyramidal Symptom Rating Scale (ESRS), and demographic and substance-use data, were compared for 40 chewers and 30 non-chewers of betel nut.

RESULTS

Betel chewers with schizophrenia scored significantly lower on the positive (P = 0.001) and negative (P = 0.002) sub-scales of the PANSS than did non-chewers. There were no significant differences in extrapyramidal symptoms or tardive dyskinesia.

CONCLUSIONS

Betel chewing is associated with milder symptomatology and avoidance of more harmful recreational drugs. These initial results indicate that longitudinal research is merited.

Insomnia and the eye of the beholder: are there clinical markers of objective sleep disturbances among adults with and without insomnia complaints?

Previous findings suggest that some who report insomnia sleep well, whereas some noncomplaining individuals sleep rather poorly. This study was conducted to determine if mood, anxiety, and sleep-related beliefs might relate to perceived sleep disturbance. Thirty-two women and 32 men (aged 40-79 years) with primary insomnia and an aged-matched sample of 61 normal sleepers (31 women, 30 men) completed 6 nocturnal sleep recordings, as well as the Beck Depression Inventory (BDI), the Trait portion of the State-Trait Anxiety Inventory (STAI-2), and the Dysfunctional Beliefs and Attitudes About Sleep Questionnaire. Sleep and interview data were used to subdivide the majority of the sample (n = 108) into objective normal sleepers and subjective insomnia sufferers who seemingly slept well and subjective normal sleepers and objective insomnia sufferers who slept poorly. The 2 subjective subgroups showed the most marked differences on most of the psychometric measures. The findings suggest that the psychological factors scrutinized in this study may mediate sleep satisfaction and/or predict objective sleep difficulties.

Talo-navicular arthrodesis for residual midfoot deformities of a previously corrected clubfoot

Triangular navicular, dorsal-lateral subluxation of the talo-navicular (TN) joint with a secondary forefoot cavovarus deformity, and degenerative changes of the TN joint are frequent causes of residual clubfoot deformity and pain in the midfoot after surgical correction. This study investigates the usefulness of TN arthrodesis to correct these deformities and to resolve symptoms resulting from these deformities. During the period from 1991-1996, the senior author performed 19 TN fusions (16 patients) for the above residual clubfoot deformities involving a painful TN joint. Eight of the procedures (seven patients) also required a lateral column shortening with a calcaneal wedge osteotomy to allow for a complete correction of the TN joint. The procedure was only performed in cases involving a hindfoot that was adequately aligned during a previous clubfoot correction. The average age of the patients at the time of surgery was 11 years (range: 4-20). One patient (bilateral procedures) was lost to follow-up. Fifteen patients (17 procedures) were followed-up for an average of four years (range: 2-6). All patients reported symptomatic improvement after the TN arthrodesis. Fourteen of the patients (15 procedures) were completely satisfied. The remaining patient (bilateral procedures) was only partially satisfied due to the subsequent development of navicular-cuneiform osteoarthritis in both feet. Two cases (2 patients) developed complications requiring a second procedure for satisfactory results. In addition, the procedure resulted in an improvement of the talus-first metatarsal angle on both antero-posterior and lateral radiographs. TN arthrodesis produced a correction of the residual clubfoot deformities of the midfoot and resulted in satisfactory clinical improvement in all the patients.

Deep vein thrombosis prophylaxis in hip fractures: a comparison of the arteriovenous impulse system and aspirin

BACKGROUND

A prospective, randomized controlled trial was used to compare the efficacy of the arteriovenous (AV) impulse system and aspirin in reducing venous thrombosis after fracture to the femoral neck.

METHODS

A total of 143 patients underwent hemiarthroplasty, after which 70 patients were treated with the AV pump and a second group of 73 patients were commenced on 325 mg of aspirin. Duplex ultrasound was used to assess both proximal and distal venous thrombi on days 7 to 10. Calf and thigh circumferences were also measured.

RESULTS

Thrombi developed in seven of the patients treated with aspirin and in four patients treated with the AV pump. No statistically significant difference could be established (p = 0.109). There was a significant reduction in both calf (p = 0.003) and thigh (p = 0.002) swelling in the group treated with the AV pump. Neither treatment group was a significant predictor of a poorer outcome by using logistical regression analysis (p = 0.258).

CONCLUSIONS

Both aspirin and the AV pump are effective in reducing thromboembolic events after hemiarthroplasty of the hip.

Patient factors related to the odds of receiving prevention services in Veterans Health Administration medical centers

OBJECTIVE

To examine the association between patient characteristics and the odds of receiving 13 health promotion/disease prevention services recommended by the US Preventive Services Task Force (USPSTF) for average-risk individuals.

METHODS

A mail survey was sent to a random sample of 68,422 veterans who obtained primary care from any of the 153 Veterans Health Administration facilities in 1996; 44,304 responded (adjusted response rate was 68%). Multivariate logistic regression models were used.

RESULTS

Demographic factors, health risk behaviors, and self-reported health were associated with the odds of receiving prevention services. Current smokers, heavy alcohol drinkers, and females were less likely to receive many health promotion services, whereas regular exercisers, overweight individuals, males, those reporting poorer health, individuals reporting high or controlled blood pressure, and those reporting high or controlled cholesterol levels were more likely to receive USPSTF-recommended prevention services.

CONCLUSION

Substantial proportions of veterans were likely to obtain prevention services recommended by the USPSTF for average-risk individuals. Nevertheless, veterans who reported being current smokers, heavy drinkers, or female were less likely to obtain these services. These subgroups may benefit from additional initiatives.

Diagnosing aneurysmal and unicameral bone cysts with magnetic resonance imaging

The differential between aneurysmal bone cysts and unicameral bone cysts usually is clear clinically and radiographically. Occasionally there are cases in which the diagnosis is not clear. Because natural history and treatment are different, the ability to distinguish between these two entities before surgery is important. The authors reviewed, in a blinded fashion, the preoperative magnetic resonance images to investigate criteria that could be used to differentiate between the two lesions. All patients had operative or pathologic confirmation of an aneurysmal bone cyst or unicameral bone cyst. The authors analyzed the preoperative magnetic resonance images of 14 patients with diagnostically difficult bone cysts (eight children with unicameral bone cysts and six children with aneurysmal bone cysts) and correlated these findings with diagnosis after biopsy or cyst aspiration and contrast injection. The presence of a double density fluid level within the lesion strongly indicated that the lesion was an aneurysmal bone cyst, rather than a unicameral bone cyst. Other criteria that suggested the lesion was an aneurysmal bone cyst were the presence of septations within the lesion and signal characteristics of low intensity on T1 images and high intensity on T2 images. The authors identified a way of helping to differentiate between aneurysmal bone cysts and unicameral bone cysts on magnetic resonance images. Double density fluid level, septation, and low signal on T1 images and high signal on T2 images strongly suggest the bone cyst in question is an aneurysmal bone cyst, rather than a unicameral bone cyst. This may be helpful before surgery for the child who has a cystic lesion for which radiographic features do not allow a clear differentiation of unicameral bone cyst from aneurysmal bone cyst.