Mars 2005 Sample Return Workshop

Convened at the request of Dr. Jurgen Rahe of the NASA Office of Space Science, the purpose of this workshop was to reexamine the science issues that will determine how an optimum sample return mission would be carried out in 2005 given the new context that has emerged for Mars exploration since the last such workshop was held (in 1987). The results and summary of discussion that took place at the meeting are contained in this volume. The community was invited to participate in the preparation of the final written report by browsing through the agenda and reading the text and viewgraphs provided by workshop participants and submitting comments for that section

Evolution of the global water cycle on Mars: The geological evidence

The geological evidence for active water cycling early in the history of Mars (Noachian geological system or heavy bombardment) consists almost exclusively of fluvial valley networks in the heavily cratered uplands of the planet. It is commonly assumed that these landforms required explanation by atmospheric processes operating above the freezing point of water and at high pressure to allow rainfall and liquid surface runoff. However, it has also been documented that nearly all valley networks probably formed by subsurface outflow and sapping erosion involving groundwater outflow prior to surface-water flow. The prolonged ground-water flow also requires extensive water cycling to maintain hydraulic gradients, but is this done via rainfall recharge, as in terrestrial environments

Fluvial valleys in the heavily cratered terrains of Mars: Evidence for paleoclimatic change?

Whether the formation of the Martian valley networks provides unequivocal evidence for drastically different climatic conditions remains debatable. Recent theoretical climate modeling precludes the existence of a temperate climate early in Mars' geological history. An alternative hypothesis suggests that Mars had a globally higher heat flow early in its geological history, bringing water tables to within 350 m of the surface. While a globally higher heat flow would initiate ground water circulation at depth, the valley networks probably required water tables to be even closer to the surface. Additionally, it was previously reported that the clustered distribution of the valley networks within terrain types, particularly in the heavily cratered highlands, suggests regional hydrological processes were important. The case for localized hydrothermal systems is summarized and estimates of both erosion volumes and of the implied water volumes for several Martian valley systems are presented

Observations of the geology and geomorphology of the 1999 Marsokhod test site

The Marsokhod rover returned data from six stations that were used to decipher the geomorphology and geology of a region not previously visited by members of the geomorphology field team. Satellite images and simulated descent images provided information about the regional setting. The landing zone was on an alluvial apron flanking a mountain block to the west and playa surface to the east. Rover color images, infrared spectra analysis of the mountains, and the apron surface provided insight into the rock composition of the nearby mountains. From the return data the geomorphology team interpreted the region to consist of compressionally deformed, ancient marine sediments and igneous rocks exposed by more recent extensional tectonics. Unconsolidated alluvial materials blanket the lower flanks of the mountains. An ancient shoreline cut into alluvial material marks a high stand of water during a past, wetter climate period. Playa sediments floor a present-day, seasonally, dry lake. Observations made by the rover using panoramic and close-up (hand specimens—scale) image data and color scene data confirmed the presence of boulders, cobbles, and fines of various provinces. Rover traverses to sites identified as geologically distinct, such as a fan, channel, shoreline, and playa, provided useful clues to the geologic interpretations. Analysis of local rocks was given context only through comparison with distant geologic features. These results demonstrated the importance of a multifaceted approach to site interpretation through comparison of interpretations derived by differing geologic techniques

Observation of the geology and geomorphology of the 1999 Marsokhod test site

The Marsokhod rover returned data from six stations that were used to decipher the geomorphology and geology of a region not previously visited by members of the geomorphology field team. Satellite images and simulated descent images provided information about the regional setting. The landing zone was on an alluvial apron flanking a mountain block to the west and a playa surface to the east. Rover color images, infrared spectra analysis of the mountains, and the apron surface provided insight into the rock composition of the nearby mountains. From the return data the geomorphology team interpreted the region to consist of compressionally deformed, ancient marine sediments and igneous rocks exposed by more recent extensional tectonics. Unconsolidated alluvial materials blanket the lower flanks of the mountains. Bn ancient shoreline cut into alluvial material marks a high stand of water during a past, wetter climate period. Playa sediments floor a present-day, seasonally, dry lake. Observations made by the rover using panoramic and close-up (hand specimens-scale) image data and color scene data confirmed the presence of boulders, cobbles, and fines of various provinces. Rover traverses to sites identified as geologically distinct, such as fan, channel, shoreline, and playa, provided useful clues to the geologic interpretations. Analysis of local rocks was given concert only through comparison with distant geologic features. These results demonstrated the importance of a multifaceted approach to site interpretation through comparison of interpretations derived by differing geologic techniques

Shift invariant preduals of ℓ₁(ℤ)

The Banach space ℓ<sub>1</sub>(ℤ) admits many non-isomorphic preduals, for example, C(K) for any compact countable space K, along with many more exotic Banach spaces. In this paper, we impose an extra condition: the predual must make the bilateral shift on ℓ<sub>1</sub>(ℤ) weak<sup>*</sup>-continuous. This is equivalent to making the natural convolution multiplication on ℓ<sub>1</sub>(ℤ) separately weak*-continuous and so turning ℓ<sub>1</sub>(ℤ) into a dual Banach algebra. We call such preduals <i>shift-invariant</i>. It is known that the only shift-invariant predual arising from the standard duality between C<sub>0</sub>(K) (for countable locally compact K) and ℓ<sub>1</sub>(ℤ) is c<sub>0</sub>(ℤ). We provide an explicit construction of an uncountable family of distinct preduals which do make the bilateral shift weak<sup>*</sup>-continuous. Using Szlenk index arguments, we show that merely as Banach spaces, these are all isomorphic to c<sub>0</sub>. We then build some theory to study such preduals, showing that they arise from certain semigroup compactifications of ℤ. This allows us to produce a large number of other examples, including non-isometric preduals, and preduals which are not Banach space isomorphic to c<sub>0</sub>

Ictal Behaviors During Nonepileptic Seizures Differ in Patients with Temporal Lobe Interictal Epileptiform EEG Activity and Patients Without Interictal Epileptiform EEG Abnormalities

Purpose: Ictal behaviors during psychogenic non-epileptic seizures (NES) vary considerably among individuals, and can closely resemble common semiologies of epileptic seizures (ES). We tested the hypothesis that behaviors during NES in patients who have temporal spikes would more closely resemble behaviors during ES in patients with temporal lobe epilepsy than would behaviors during NES in patients who do not have EEG spikes. Methods: We identified 20 patients who had interictal temporal EEG spikes and EEG-video recorded NES (Study Group), 133 patients with temporal EEG spikes and recorded ES, without NES (Epileptic Group), and 24 patients with recorded NES and no epileptiform EEG abnormalities, without ES (Nonepileptic Group). Results: The hypothesis was supported with regard to ictal motor behaviors. Motionless staring or complex automatisms occurred mainly during NES in the Study Group and during ES in the Epileptic Group. In contrast, convulsive movements or flaccid falls were most common during NES in the Nonepileptic Group. Duration of unresponsiveness was longer, and there were fewer postictal states in NES both in the Study and Non-epileptic Groups. Unresponsiveness was briefer and postictal states were more consistent in ES in the Epileptic Group, however. Conclusions: Stereotyped motor activities during NES presumably represent learned behaviors. Processes underlying acquisition of ictal behaviors of NES probably differ in patients with interictal epileptiform EEG abnormalities compared to those without. Prior experiences and temporal lobe dysfunctions that are associated with epilepsy, and psychological characteristics that are unrelated to interictal epileptic dysfunctions, may determine ictal behaviors during NES.Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/65913/1/j.1528-1157.1998.tb01355.x.pd

Residual Human Immunodeficiency Virus (HIV) Type 1 RNA and DNA in Lymph Nodes and HIV RNA in Genital Secretions and in Cerebrospinal Fluid after Suppression of Viremia for 2 Years

Residual viral replication persists in a significant proportion of human immunodeficiency virus (HIV)-infected patients receiving potent antiretroviral therapy. To determine the source of this virus, levels of HIV RNA and DNA from lymphoid tissues and levels of viral RNA in serum, cerebrospinal fluid (CSF), and genital secretions in 28 patients treated for ⩽2.5 years with indinavir, zidovudine, and lamivudine were examined. Both HIV RNA and DNA remained detectable in all lymph nodes. In contrast, HIV RNA was not detected in 20 of 23 genital secretions or in any of 13 CSF samples after 2 years of treatment. HIV envelope sequence data from plasma and lymph nodes from 4 patients demonstrated sequence divergence, which suggests varying degrees of residual viral replication in 3 and absence in 1 patient. In patients receiving potent antiretroviral therapy, the greatest virus burden may continue to be in lymphoid tissues rather than in central nervous system or genitourinary compartment

Abacavir, efavirenz, didanosine, with or without hydroxyurea, in HIV-infected adults failing initial nucleoside/protease inhibitor-containing regimens

BACKGROUND: Hydroxyurea (HU) is an immunomodulatory agent that has been documented to enhance the antiretroviral activity of nucleoside reverse transcriptase inhibitors, such as abacavir (ABC) and didanosine (ddI), and would be expected to improve virologic efficacy. METHODS: A 48-week, phase IV, multicenter, open-label, proof-of-concept clinical trial was conducted to evaluate second-line, protease inhibitor (PI)-sparing therapy with ABC/efavirenz (EFV)/ddI plus HU or without HU in HIV-infected subjects failing to achieve HIV-1 RNA ≤ 400 copies/mL after ≥ 16 weeks of treatment with lamivudine/zidovudine or lamivudine/stavudine, plus 1 or 2 PIs. Subjects were assigned to ABC (300 mg twice daily)/ EFV (600 mg once daily)/ ddI (400 mg once daily) plus HU (500 mg twice daily) (n = 30) or this regimen without HU (n = 24). RESULTS: Baseline mean HIV-1 RNA was 3.86 log(10 )copies/mL and CD4+ cell count was 345 cells/mm(3). A similar percentage of subjects in the non-HU arm (58%) and HU arm (53%) completed the study. Intent-to-treat: missing = failure analysis showed no differences in proportions of subjects in the non-HU and HU arms achieving undetectable plasma HIV-1 RNA levels at week 24 (<400 copies/mL: 58% [14/24] vs 57% [17/30], P = 0.899; <50 copies/mL (50% [12/24] vs 47% [14/30], P = 0.780). Median change from baseline in CD4+ cell count in the non-HU and HU arms at week 48 was +114 cells/mm(3 )and -63 cells/mm(3 )(P = 0.007), respectively. Both regimens were generally well tolerated, although more subjects in the HU arm withdrew prematurely from the study due to adverse events (23% vs 4%). Four cases of possible ABC-related hypersensitivity were observed. CONCLUSION: ABC/EFV/ddI was an effective and well-tolerated second-line regimen for nucleoside/PI-experienced HIV-infected subjects. The addition of HU blunted the CD4+ cell response, did not appear to enhance antiviral activity, and resulted in more treatment-limiting adverse events

Statistical Methods in Recent HIV Noninferiority Trials: Reanalysis of 11 Trials

Background: In recent years the ‘‘noninferiority’ ’ trial has emerged as the new standard design for HIV drug development among antiretroviral patients often with a primary endpoint based on the difference in success rates between the two treatment groups. Different statistical methods have been introduced to provide confidence intervals for that difference. The main objective is to investigate whether the choice of the statistical method changes the conclusion of the trials. Methods: We presented 11 trials published in 2010 using a difference in proportions as the primary endpoint. In these trials, 5 different statistical methods have been used to estimate such confidence intervals. The five methods are described and applied to data from the 11 trials. The noninferiority of the new treatment is not demonstrated if the prespecified noninferiority margin it includes in the confidence interval of the treatment difference. Results: Results indicated that confidence intervals can be quite different according to the method used. In many situations, however, conclusions of the trials are not altered because point estimates of the treatment difference were too far from the prespecified noninferiority margins. Nevertheless, in few trials the use of different statistical methods led to different conclusions. In particular the use of ‘‘exact’ ’ methods can be very confusing. Conclusion: Statistical methods used to estimate confidence intervals in noninferiority trials have a strong impact on th