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Mobile phones and wrong numbers: how Maasai agro-pastoralists form and use accidental social ties in East Africa
Mobile phones are recognized as important new tools for rural development in the Global South, but few studies have
examined how phones can shape social networks. This study documents a new type of social tie, enabled by mobile phones, that to our
knowledge has not previously been discussed in academic literature. In 2018, we discovered that Maasai pastoralists in northern Tanzania
create new social ties through wrong numbers, a phenomenon with implications for theory on social networks and path dependency.
We used a mixed ethnographic and survey-based design to examine the following: (1) the conditions under which wrong number
connections (WNCs) are made; (2) the incidence of these connections in the study area; and (3) the association between WNCs and
multiple livelihood strategies. Working in 10 rural communities in Tanzania, we conducted 16 group interviews with men about their
phone use and found that WNCs are diverse and can provide households with important information, resources, and opportunities
from an expansive geographic area. (Nine separate interviews with groups of women revealed that women do not create WNCs.) Based
on early qualitative findings, we designed and conducted a standardized survey with 317 household heads. We found that 46% of
respondents have had WNCs. Furthermore, multivariate regression models show a significant association between WNCs and the
controversial practice of leasing land in one district. Taken together, our findings show that WNCs can be seen as innovations in social
networking that reduce path dependency, increase the range of potential outcomes, and hold important implications for rural livelihoods
in East Africa
Kritisi Desain Pseudo Elastis Pada Bangunan Beraturan 6- Dan 10- Lantai Dengan Denah Persegi Di Wilayah 6 Peta Gempa Indonesia
Pseudo Elastis adalah metode alternatif yang dikembangkan dalam perencanaan bangunan terhadap gempa dengan menggunakan pola keruntuhan Partial Side Sway Mechanism. Beberapa kolom didesain dengan suatu faktor pengali (FP) sebagai pembesar gaya untuk menjaga agar kolom tetap elastis selama terkena beban gempa, sedangkan kolom lainnya dan balok diijinkan mengalami sendi plastis. Metode ini tidak lagi berdasarkan desain kapasitas seperti pada umumnya, melainkan berdasarkan beban kombinasi yang bekerja. Tujuan dari penelitian ini adalah mengkritisi apakah asumsi pada konsep Pseudo Elastis mengenai distribusi gaya geser pada kolom interior ke kolom eksterior sudah benar dan bangunan memenuhi pola keruntuhan Partial Side Sway Mechanism. Bangunan yang diteliti adalah bangunan beraturan berbentuk persegi, 6- dan 10-lantai di wilayah 6 peta gempa Indonesia. Tulangan balok direncanakan sedekat mungkin dengan perhitungan teoritis. Distribusi gaya geser dan kinerja bangunan diuji dengan analisis Time History Nonlinear menggunakan program SAP2000v.11. Hasil penelitian menunjukkan bahwa distribusi gaya geser pada kolom interior tidak tersalurkan ke kolom eksterior dan pola keruntuhan Partial Side Sway Mechanism masih belum tercapai
A method for sensitivity analysis to assess the effects of measurement error in multiple exposure variables using external validation data
Measurement error in self-reported dietary intakes is known to bias the association between dietary intake and a health outcome of interest such as risk of a disease. The association can be distorted further by mismeasured confounders, leading to invalid results and conclusions. It is, however, difficult to adjust for the bias in the association when there is no internal validation data
Sampling constrained probability distributions using Spherical Augmentation
Statistical models with constrained probability distributions are abundant in
machine learning. Some examples include regression models with norm constraints
(e.g., Lasso), probit, many copula models, and latent Dirichlet allocation
(LDA). Bayesian inference involving probability distributions confined to
constrained domains could be quite challenging for commonly used sampling
algorithms. In this paper, we propose a novel augmentation technique that
handles a wide range of constraints by mapping the constrained domain to a
sphere in the augmented space. By moving freely on the surface of this sphere,
sampling algorithms handle constraints implicitly and generate proposals that
remain within boundaries when mapped back to the original space. Our proposed
method, called {Spherical Augmentation}, provides a mathematically natural and
computationally efficient framework for sampling from constrained probability
distributions. We show the advantages of our method over state-of-the-art
sampling algorithms, such as exact Hamiltonian Monte Carlo, using several
examples including truncated Gaussian distributions, Bayesian Lasso, Bayesian
bridge regression, reconstruction of quantized stationary Gaussian process, and
LDA for topic modeling.Comment: 41 pages, 13 figure
A family of thermostable fungal cellulases created by structure-guided recombination
SCHEMA structure-guided recombination of 3 fungal class II cellobiohydrolases (CBH II cellulases) has yielded a collection of highly thermostable CBH II chimeras. Twenty-three of 48 genes sampled from the 6,561 possible chimeric sequences were secreted by the Saccharomyces cerevisiae heterologous host in catalytically active form. Five of these chimeras have half-lives of thermal inactivation at 63°C that are greater than the most stable parent, CBH II enzyme from the thermophilic fungus Humicola insolens, which suggests that this chimera collection contains hundreds of highly stable cellulases. Twenty-five new sequences were designed based on mathematical modeling of the thermostabilities for the first set of chimeras. Ten of these sequences were expressed in active form; all 10 retained more activity than H. insolens CBH II after incubation at 63°C. The total of 15 validated thermostable CBH II enzymes have high sequence diversity, differing from their closest natural homologs at up to 63 amino acid positions. Selected purified thermostable chimeras hydrolyzed phosphoric acid swollen cellulose at temperatures 7 to 15°C higher than the parent enzymes. These chimeras also hydrolyzed as much or more cellulose than the parent CBH II enzymes in long-time cellulose hydrolysis assays and had pH/activity profiles as broad, or broader than, the parent enzymes. Generating this group of diverse, thermostable fungal CBH II chimeras is the first step in building an inventory of stable cellulases from which optimized enzyme mixtures for biomass conversion can be formulated
RNA secondary structure formation: a solvable model of heteropolymer folding
The statistical mechanics of heteropolymer structure formation is studied in
the context of RNA secondary structures. A designed RNA sequence biased
energetically towards a particular native structure (a hairpin) is used to
study the transition between the native and molten phase of the RNA as a
function of temperature. The transition is driven by a competition between the
energy gained from the polymer's overlap with the native structure and the
entropic gain of forming random contacts. A simplified Go-like model is
proposed and solved exactly. The predicted critical behavior is verified via
exact numerical enumeration of a large ensemble of similarly designed
sequences.Comment: 4 pages including 2 figure
Simple models of protein folding and of non--conventional drug design
While all the information required for the folding of a protein is contained
in its amino acid sequence, one has not yet learned how to extract this
information to predict the three--dimensional, biologically active, native
conformation of a protein whose sequence is known. Using insight obtained from
simple model simulations of the folding of proteins, in particular of the fact
that this phenomenon is essentially controlled by conserved (native) contacts
among (few) strongly interacting ("hot"), as a rule hydrophobic, amino acids,
which also stabilize local elementary structures (LES, hidden, incipient
secondary structures like --helices and --sheets) formed early
in the folding process and leading to the postcritical folding nucleus (i.e.,
the minimum set of native contacts which bring the system pass beyond the
highest free--energy barrier found in the whole folding process) it is possible
to work out a succesful strategy for reading the native structure of designed
proteins from the knowledge of only their amino acid sequence and of the
contact energies among the amino acids. Because LES have undergone millions of
years of evolution to selectively dock to their complementary structures, small
peptides made out of the same amino acids as the LES are expected to
selectively attach to the newly expressed (unfolded) protein and inhibit its
folding, or to the native (fluctuating) native conformation and denaturate it.
These peptides, or their mimetic molecules, can thus be used as effective
non--conventional drugs to those already existing (and directed at neutralizing
the active site of enzymes), displaying the advantage of not suffering from the
uprise of resistance
On the stability of renormalizable expansions in three-dimensional gravity
Preliminary investigations are made for the stability of the expansion
in three-dimensional gravity coupled to various matter fields, which are
power-counting renormalizable. For unitary matters, a tachyonic pole appears in
the spin-2 part of the leading graviton propagator, which implies the unstable
flat space-time, unless the higher-derivative terms are introduced. As another
possibility to avoid this spin-2 tachyon, we propose Einstein gravity coupled
to non-unitary matters. It turns out that a tachyon appears in the spin-0 or -1
part for any linear gauges in this case, but it can be removed if non-minimally
coupled scalars are included. We suggest an interesting model which may be
stable and possess an ultraviolet fixed point.Comment: 32 pages. (A further discussion to avoid tachyons is included. To be
Published in Physical Review D.
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Cardiac Biomarkers and Risk of Atrial Fibrillation in Chronic Kidney Disease: The CRIC Study.
Background We tested associations of cardiac biomarkers of myocardial stretch, injury, inflammation, and fibrosis with the risk of incident atrial fibrillation (AF) in a prospective study of chronic kidney disease patients. Methods and Results The study sample was 3053 participants with chronic kidney disease in the multicenter CRIC (Chronic Renal Insufficiency Cohort) study who were not identified as having AF at baseline. Cardiac biomarkers, measured at baseline, were NT-proBNP (N-terminal pro-B-type natriuretic peptide), high-sensitivity troponin T, galectin-3, growth differentiation factor-15, and soluble ST-2. Incident AF ("AF event") was defined as a hospitalization for AF. During a median follow-up of 8 years, 279 (9%) participants developed a new AF event. In adjusted models, higher baseline log-transformed NT-proBNP (N-terminal pro-B-type natriuretic peptide) was associated with incident AF (adjusted hazard ratio [HR] per SD higher concentration: 2.11; 95% CI, 1.75, 2.55), as was log-high-sensitivity troponin T (HR 1.42; 95% CI, 1.20, 1.68). These associations showed a dose-response relationship in categorical analyses. Although log-soluble ST-2 was associated with AF risk in continuous models (HR per SD higher concentration 1.35; 95% CI, 1.16, 1.58), this association was not consistent in categorical analyses. Log-galectin-3 (HR 1.05; 95% CI, 0.91, 1.22) and log-growth differentiation factor-15 (HR 1.16; 95% CI, 0.96, 1.40) were not significantly associated with incident AF. Conclusions We found strong associations between higher NT-proBNP (N-terminal pro-B-type natriuretic peptide) and high-sensitivity troponin T concentrations, and the risk of incident AF in a large cohort of participants with chronic kidney disease. Increased atrial myocardial stretch and myocardial cell injury may be implicated in the high burden of AF in patients with chronic kidney disease
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