We construct uncountably many finitely generated, pairwise non-isomorphic torsion-free groups, all of which fall into the same quasi-isometry class. This is done by considering Schur covering groups and group cohomology, with the necessary geometric ingredient coming from the theory of bounded-valued cohomology.
In sub-Saharan Africa, population growth coupled with weak or missing markets for clean energy means that the absolute number of people relying on woodfuels for cooking is growing. Charcoal, which has distinctly different environmental and economic implications from firewood, has become one of the most consumed fuels in the region. However, among rural populations, the drivers and consequences of charcoal use remain under-studied. We examine rural woodfuel dynamics in Malawi, a majority rural country with high poverty, rapid population growth, lagging economic development, and abundant but rapidly declining forest resources. We examine how household energy transitions are influenced by concurrent demographic, economic, and land use changes. Using four waves of national household surveys and satellite-derived forest cover datasets, we investigate trends in household energy consumption, identify factors driving rural household fuel choices, and characterize geographic patterns of forest cover loss during 2004–2020. During this time, the share of rural households using charcoal grew from 3.9% to 13.4%. Rural households that are smaller, headed by younger individuals, and are asset-rich but land-poor had greater odds of using charcoal compared to firewood, indicating that rural livelihood dynamics have important consequences for household energy transitions. Several protected areas have experienced > 20% forest cover loss since 2001, characterized by geographic patterns consistent with unsanctioned woodfuel extraction. These findings emphasize a renewed need for integrated natural resources, energy, and livelihoods management strategies. Our insights provide information for policy makers to better predict and understand the continued growth of charcoal’s popularity in Malawi and similar contexts.
A flexible approach to crystalline compounds was developed: lipophilic structures of interest were connected to pro-crystalline semicarbazone reagents via copper-catalyzed azide-alkyne cycloaddition or Brønsted-Lowry acid-base reactions. A variety of lipophilic structures, including esters, carbamates, acids and amines were converted into crystalline solids as determined by powder X-ray diffraction (mp 134 to >240 °C). Single crystal X-ray diffraction revealed hydrogen-bond interactions between the semicarbazone and charged ammonium or acetate groups that may aid in ordering the crystals.
Purpose The biomechanics of surgically treated metacarpal base fractures are poorly described. We hypothesized that intramedullary threaded nail (IMTN) fixation and dorsal plate and screw (DPS) fixation would perform similarly in multiple fracture locations approaching the metacarpal base. Methods Sixty-four metacarpals from eight matched pair cadaveric hands were stripped. Matched pairs were randomly divided into four cohorts based on fracture distance from the metacarpal base. Transverse osteotomies were created at 50%, 35%, 25%, and 15% of the total metacarpal length, measured from the metacarpal base. The 50% cohort served as a control. For each cohort, paired metacarpals were randomized to either DPS or IMTN fixation groups. All specimens were cyclically loaded in 3-point bending for 2,000 cycles at 70 N, 2,000 cycles at 120 N, and then loaded to failure. Bending stiffness, cycles to failure, and peak load to failure (LTF) were collected. Results Peak bending stiffness and peak LTF were not significantly different in the 15%, 25%, or 35% groups compared to the 50% control for both IMTN and DPS fixation. Direct comparison of IMTN and DPS fixation at each osteotomy level yielded no significant differences in LTF or bending stiffness. There was a nonsignificant trend toward higher LTF and bending stiffness with DPS fixation in more proximal fractures. Conclusions Peak LTF and bending stiffness were not significantly different for IMTN or DPS fixation in fractures located as proximally as 15% from the metacarpal base. Furthermore, both IMTN and DPS fixation had no significant differences in peak bending stiffness and LTF for metacarpal fractures as proximal as 15% from the base compared to a 50% control. Clinical relevance When managing proximal metacarpal fractures surgeons can expect no significant difference in stiffness or LTF using either DPS or IMTN fixation with values comparable to those seen when treating a midshaft metacarpal fracture.
Many biomedical studies collect high-dimensional medical imaging data to identify biomarkers for the detection, diagnosis, and treatment of human diseases. Consequently, it is crucial to develop accurate models that can predict a wide range of clinical outcomes (both discrete and continuous) based on imaging data. By treating imaging predictors as functional data, we propose a residual-based alternative partial least squares (RAPLS) model for a broad class of generalized functional linear models that incorporate both functional and scalar covariates. Our RAPLS method extends the alternative partial least squares (APLS) algorithm iteratively to accommodate additional scalar covariates and non-continuous outcomes. We establish the convergence rate of the RAPLS estimator for the unknown slope function and, with an additional calibration step, we prove the asymptotic normality and efficiency of the calibrated RAPLS estimator for the scalar parameters. The effectiveness of the RAPLS algorithm is demonstrated through multiple simulation studies and an application predicting Alzheimer's disease progression using neuroimaging data from the Alzheimer's Disease Neuroimaging Initiative (ADNI).
