Quantification of surface layer turbulence using sensible heat values from energy balance versus aerodynamic methods.

Surface layer optical turbulence values in the form of the refractive index structure function C n2 are often calculated from surface layer temperature, moisture, and wind characteristics and compared to measurements from sonic anemometers, differential temperature sensors, and imaging systems. A key derived component needed in the surface layer turbulence calculations is the sensible heat value. Typically, the sensible heat is calculated using the bulk aerodynamic method that assumes a certain surface roughness and a friction velocity that approximates the turbulence drag on temperature and moisture mixing from the change in the average surface layer vertical wind velocity. These assumptions/approximations generally only apply in free convection conditions. To obtain the sensible heat, a more robust method, which applies when free convection conditions are not occurring, is via an energy balance method such as the Bowen ratio method. The use of the Bowen ratio--the ratio of sensible heat flux to latent heat flux--allows a more direct assessment of the optical turbulence-driving surface layer sensible heat flux than do more traditional assessments of surface layer sensible heat flux. This study compares surface layer C n2 values using sensible heat values from the bulk aerodynamic and energy balance methods to quantifications from sonic anemometers posted at different heights on a sensor tower. The research shows that the sensible heat obtained via the Bowen ratio method provides a simpler, more reliable, and more accurate way to calculate surface layer C n2 values than what is required to make such calculations from bulk aerodynamic method-obtained sensible heat.

Investigating turbulence distribution in the lower atmosphere using time-lapse imagery from a camera bank.

The atmosphere's surface layer (first 50-100 m above the ground) is extremely dynamic and is influenced by surface radiative properties, roughness, and atmospheric stability. Understanding the distribution of turbulence in the surface layer is critical to many applications, such as directed energy and free space optical communications. Several measurement campaigns in the past have relied on weather balloons or sonic detection and ranging (SODAR) to measure turbulence up to the atmospheric boundary layer. However, these campaigns had limited measurements near the surface. We have developed a time-lapse imaging technique to profile atmospheric turbulence from turbulence-induced differential motion or tilts between features on a distant target, sensed between pairs of cameras in a camera bank. This is a low-cost and portable approach to remotely sense turbulence from a single site without the deployment of sensors at the target location. It is thus an excellent approach to study the distribution of turbulence in low altitudes with sufficiently high resolution. In the present work, the potential of this technique was demonstrated. We tested the method over a path with constant turbulence. We explored the turbulence distribution with height in the first 20 m above the ground by imaging a 30 m water tower over a flat terrain on three clear days in summer. In addition, we analyzed time-lapse data from a second water tower over a sloped terrain. In most of the turbulence profiles extracted from these images, the drop in turbulence with altitude in the first 15 m or so above the ground showed a h m dependence, where the exponent m varied from -0.3 to -1.0, quite contrary to the widely used value of -4/3.

Modeling net ecosystem carbon balance and loss in coastal wetlands exposed to sea-level rise and saltwater intrusion.

Coastal wetlands are globally important stores of carbon (C). However, accelerated sea-level rise (SLR), increased saltwater intrusion, and modified freshwater discharge can contribute to the collapse of peat marshes, converting coastal peatlands into open water. Applying results from multiple experiments from sawgrass (Cladium jamaicense)-dominated freshwater and brackish water marshes in the Florida Coastal Everglades, we developed a system-level mechanistic peat elevation model (EvPEM). We applied the model to simulate net ecosystem C balance (NECB) and peat elevation in response to elevated salinity under inundation and drought exposure. Using a mass C balance approach, we estimated net gain in C and corresponding export of aquatic fluxes ( F AQ $$ {F}_{\mathrm{AQ}} $$ ) in the freshwater marsh under ambient conditions (NECB = 1119 ± 229 gC m-2  year-1 ; FAQ  = 317 ± 186 gC m-2  year-1 ). In contrast, the brackish water marsh exhibited substantial peat loss and aquatic C export with ambient (NECB = -366 ± 15 gC m-2  year-1 ; FAQ  = 311 ± 30 gC m-2  year-1 ) and elevated salinity (NECB = -594 ± 94 gC m-2  year-1 ; FAQ  = 729 ± 142 gC m-2  year-1 ) under extended exposed conditions. Further, mass balance suggests a considerable decline in soil C and corresponding elevation loss with elevated salinity and seasonal dry-down. Applying EvPEM, we developed critical marsh net primary productivity (NPP) thresholds as a function of salinity to simulate accumulating, steady-state, and collapsing peat elevations. The optimization showed that ~150-1070 gC m-2  year-1 NPP could support a stable peat elevation (elevation change ≈ SLR), with the corresponding salinity ranging from 1 to 20 ppt under increasing inundation levels. The C budgeting and modeling illustrate the impacts of saltwater intrusion, inundation, and seasonal dry-down and reduce uncertainties in understanding the fate of coastal peat wetlands with SLR and freshwater restoration. The modeling results provide management targets for hydrologic restoration based on the ecological conditions needed to reduce the vulnerability of the Everglades' peat marshes to collapse. The approach can be extended to other coastal peatlands to quantify C loss and improve understanding of the influence of the biological controls on wetland C storage changes for coastal management.

Self-Assembly Synthesis of a [2]Catenane CoII Single-Molecule Magnet.

We describe herein the self-assembly synthesis of an octanuclear CoII [2]catenane {[Co4 (H2 L)6 ]2 16+ } formed by the mechanical interlocking of two {[Co4 (H2 L)6 ]8+ } rectangles of unprecedented topology. Subtle manipulation of the synthetic conditions allows the isolation of a mixed-valence [Co2 III /Co2 II ]10+ non-catenated rectangle. The CoII centers in the [2]catenane exhibit slow relaxation of their magnetic moment, i. e. single-molecule magnet properties, dominated by quantum tunneling and Raman relaxation processes. This work shows that metallo-supramolecular chemistry can precisely control the organization of single-molecule magnets in topologically complex arrangements.

The First Sulfate-Pillared Hybrid Ultramicroporous Material, SOFOUR-1-Zn, and Its Acetylene Capture Properties.

Hybrid ultramicroporous materials, HUMs, are comprised of metal cations linked by combinations of inorganic and organic ligands. Their modular nature makes them amenable to crystal engineering studies, which have thus far afforded four HUM platforms (as classified by the inorganic linkers). HUMs are of practical interest because of their benchmark gas separation performance for several industrial gas mixtures. We report herein design and gram-scale synthesis of the prototypal sulfate-linked HUM, the fsc topology coordination network ([Zn(tepb)(SO4 )]n ), SOFOUR-1-Zn, tepb=(tetra(4-pyridyl)benzene). Alignment of the sulfate anions enables strong binding to C2 H2 via O⋅⋅⋅HC interactions but weak CO2 binding, affording a new benchmark for the difference between C2 H2 and CO2 heats of sorption at low loading (ΔQst =24 kJ mol-1 ). Dynamic column breakthrough studies afforded fuel-grade C2 H2 from trace (1 : 99) or 1 : 1 C2 H2 /CO2 mixtures, outperforming its SiF6 2- analogue, SIFSIX-22-Zn.

MRI monitoring of macaque monkeys in neuroscience: Case studies, resource and normative data comparisons.

Information from Magnetic Resonance Imaging (MRI) is useful for diagnosis and treatment management of human neurological patients. MRI monitoring might also prove useful for non-human animals involved in neuroscience research provided that MRI is available and feasible and that there are no MRI contra-indications precluding scanning. However, MRI monitoring is not established in macaques and a resource is urgently needed that could grow with scientific community contributions. Here we show the utility and potential benefits of MRI-based monitoring in a few diverse cases with macaque monkeys. We also establish a PRIMatE MRI Monitoring (PRIME-MRM) resource within the PRIMatE Data Exchange (PRIME-DE) and quantitatively compare the cases to normative information drawn from MRI data from typical macaques in PRIME-DE. In the cases, the monkeys presented with no or mild/moderate clinical signs, were well otherwise and MRI scanning did not present a significant increase in welfare impact. Therefore, they were identified as suitable candidates for clinical investigation, MRI-based monitoring and treatment. For each case, we show MRI quantification of internal controls in relation to treatment steps and comparisons with normative data in typical monkeys drawn from PRIME-DE. We found that MRI assists in precise and early diagnosis of cerebral events and can be useful for visualising, treating and quantifying treatment response. The scientific community could now grow the PRIME-MRM resource with other cases and larger samples to further assess and increase the evidence base on the benefits of MRI monitoring of primates, complementing the animals' clinical monitoring and treatment regime.

Exploring the dynamics of Zr-based metal-organic frameworks containing mechanically interlocked molecular shuttles.

Zr(iv) metal-organic frameworks (MOFs) UiO-68 and PCN-57, containing triphenylene dicarboxylate (TPDC) and tetramethyl-triphenylene dicarboxylate (TTDC) linkers, respectively, were doped with an H-shaped tetracarboxylate linker that contains a [2]rotaxane molecular shuttle. The new MOFs, UWDM-8 and UWDM-9, contain a [2]rotaxane crossbar spanning the tetrahedral cavities of the fcu topology while the octahedral cavities remain empty. 13C solid-state NMR (SSNMR) spectra and solution 1H NMR spectra verified that the [2]rotaxanes were included as designed. Variable-temperature (VT) cross polarization (CP) magic-angle spinning (MAS) 13C SSNMR was used to explore the translational motion of the macrocyclic ring in both MOFs. The SSNMR results clearly show that the structure of the linker (TPDCvs.TTDC) affects the shuttling rate of the macrocyclic ring, although questions remain as to how rotation of the central phenylene unit of the strut might also affect the motion of the macrocycle.

Performance of a fully-automated system on a WHO malaria microscopy evaluation slide set.

BACKGROUND: Manual microscopy remains a widely-used tool for malaria diagnosis and clinical studies, but it has inconsistent quality in the field due to variability in training and field practices. Automated diagnostic systems based on machine learning hold promise to improve quality and reproducibility of field microscopy. The World Health Organization (WHO) has designed a 55-slide set (WHO 55) for their External Competence Assessment of Malaria Microscopists (ECAMM) programme, which can also serve as a valuable benchmark for automated systems. The performance of a fully-automated malaria diagnostic system, EasyScan GO, on a WHO 55 slide set was evaluated. METHODS: The WHO 55 slide set is designed to evaluate microscopist competence in three areas of malaria diagnosis using Giemsa-stained blood films, focused on crucial field needs: malaria parasite detection, malaria parasite species identification (ID), and malaria parasite quantitation. The EasyScan GO is a fully-automated system that combines scanning of Giemsa-stained blood films with assessment algorithms to deliver malaria diagnoses. This system was tested on a WHO 55 slide set. RESULTS: The EasyScan GO achieved 94.3 % detection accuracy, 82.9 % species ID accuracy, and 50 % quantitation accuracy, corresponding to WHO microscopy competence Levels 1, 2, and 1, respectively. This is, to our knowledge, the best performance of a fully-automated system on a WHO 55 set. CONCLUSIONS: EasyScan GO's expert ratings in detection and quantitation on the WHO 55 slide set point towards its potential value in drug efficacy use-cases, as well as in some case management situations with less stringent species ID needs. Improved runtime may enable use in general case management settings.

Sequence learning modulates neural responses and oscillatory coupling in human and monkey auditory cortex.

Learning complex ordering relationships between sensory events in a sequence is fundamental for animal perception and human communication. While it is known that rhythmic sensory events can entrain brain oscillations at different frequencies, how learning and prior experience with sequencing relationships affect neocortical oscillations and neuronal responses is poorly understood. We used an implicit sequence learning paradigm (an "artificial grammar") in which humans and monkeys were exposed to sequences of nonsense words with regularities in the ordering relationships between the words. We then recorded neural responses directly from the auditory cortex in both species in response to novel legal sequences or ones violating specific ordering relationships. Neural oscillations in both monkeys and humans in response to the nonsense word sequences show strikingly similar hierarchically nested low-frequency phase and high-gamma amplitude coupling, establishing this form of oscillatory coupling-previously associated with speech processing in the human auditory cortex-as an evolutionarily conserved biological process. Moreover, learned ordering relationships modulate the observed form of neural oscillatory coupling in both species, with temporally distinct neural oscillatory effects that appear to coordinate neuronal responses in the monkeys. This study identifies the conserved auditory cortical neural signatures involved in monitoring learned sequencing operations, evident as modulations of transient coupling and neuronal responses to temporally structured sensory input.

Periphyton as an indicator of saltwater intrusion into freshwater wetlands: insights from experimental manipulations.

Saltwater intrusion has particularly large impacts on karstic wetlands of the Caribbean Basin due to their porous, carbonate bedrock and low elevation. Increases in salinity and phosphorus (P) accompanying saltwater intrusion into these freshwater, P-limited wetlands are expected to alter biogeochemical cycles along with the structure and function of plant and algal communities. Calcareous periphyton is a characteristic feature of karstic wetlands and plays a central role in trophic dynamics, carbon storage, and nutrient cycling. Periphyton is extremely sensitive to water quality and quantity, but the effects of saltwater intrusion on these microbial mats remain to be understood. We conducted an ex situ mesocosm experiment to test the independent and combined effects of elevated salinity and P on the productivity, nutrient content, and diatom composition of calcareous periphyton from the Florida Everglades. We measured periphyton total carbon, nitrogen, and P concentrations and used settlement plates to measure periphyton accumulation rates and diatom species composition. The light and dark bottle method was used to measure periphyton productivity and respiration. We found that exposure to ~1 g P·m-2 ·yr-1 significantly increased periphyton mat total P concentrations, but had no effect on any other response variable. Mats exposed to elevated salinity (~22 kg salt·m-2 ·yr-1 ) had significantly lower total carbon and tended to have lower biomass and reduced productivity and respiration rates; however, mats exposed to salinity and P simultaneously had greater gross and net productivity. We found strong diatom species dissimilarity between fresh- and saltwater-treated periphyton, while P additions only elicited compositional changes in periphyton also treated with saltwater. This study contributes to our understanding of how the ecologically important calcareous periphyton mats unique to karstic, freshwater wetlands respond to increased salinity and P caused saltwater intrusion and provides a guide to diatom indicator taxa for these two important environmental drivers.

One-pot synthesis of porphyrin-based [5]rotaxanes.

A one-pot reaction is used to make a series of [5]rotaxanes. The protocol involves simultaneous threading-followed-by-stoppering to trap a macrocycle (dibenzo[24]crown-8, DB24C8) on an axle to form a mechanically interlocked molecule (MIM) - in this case a rotaxane - and the condensation of an aldehyde with a pyrrole to form a porphyrin precursor. For each [5]rotaxane, a different combination of recognition site and stoppering group was used; the protonation state of the [5]rotaxane can be used to generate different co-conformational states for each [5]rotaxane making these systems potential multi-state switches for further study in solution or the solid-state.

Endogenous Endophthalmitis: yield of the diagnostic evaluation.

BACKGROUND: Endogenous endophthalmitis is an infection of the eye secondary to sepsis, occurring in 0.04-0.5% of bacteremia or fungemia. Risk factors include intravenous drug abuse (IVDA), diabetes, indwelling catheters, and immune suppression. Many patients have known or suspected bacteremia or fungemia; however, culture yield is reported to be low (approximately 50%). The purpose of this study is to elucidate the yield of diagnostic evaluation including microbial cultures over a 6.5 year period at an academic center in the United States. METHODS: Retrospective chart review of patients with endogenous endophthalmitis at the University of Florida from June 2011 to February 2018. RESULTS: Included are 40 eyes of 35 patients. Endophthalmitis was secondary to an endogenous source in 23.5% of all endophthalmitis cases observed. Intraocular culture positivity was 28.6% overall but was 0% after initiation of systemic antibiotics. Most commonly identified organisms from the eye were coagulase-negative Staphylococcus and Candida. Blood culture positivity was 48.6%, most commonly Staphylococcus. IVDA was noted with increasing frequency as a risk factor. Diagnosis of endophthalmitis upon hospital admission was associated with a higher intraocular culture positivity (P = 0.040) and a shorter hospital stay (P = 0.035). Computed tomography (CT) and magnetic resonance imaging (MRI) were the highest yield imaging modalities; X-ray and non-ocular ultrasound were less diagnostically useful. Echocardiogram was positive by transesophageal route (TEE) in 22% and in 9% by transthoracic (TTE) testing. Following discharge from the hospital, 48.4% of patients failed to follow up with outpatient ophthalmology. CONCLUSIONS: Based on the results of this study, the interdisciplinary team should consider directed imaging, eye cultures prior to antimicrobial administration, thorough history for IVDA, and caution with premature discharge from the hospital.

Proximal Femoral Deformity Following Threaded Prophylactic Fixation for Slipped Capital Femoral Epiphysis: Risk Stratification Using the Modified Oxford Score.

BACKGROUND: This study assesses the effect of skeletal maturity on the development of iatrogenic proximal femoral deformity following threaded prophylactic screw fixation in patients presenting with unilateral slipped capital femoral epiphysis (SCFE). METHODS: Children who underwent threaded screw prophylaxis of the uninvolved hip (Group P) and those who were observed with no prophylaxis (Group N) on presentation with unilateral SCFE were compared. Skeletal maturity was assessed with the Modified Oxford Score (MOS). Proximal femoral morphology was characterized by femoral neck length, femoral neck width, neck shaft angle, and trochanteric femoral head overlap percentage (TFHOP). Femoral head deformity at final follow-up was characterized as spherical (Type 1), mildly aspherical (Type 2), or ovoid (Type 3). Analysis of variance and t test were used to compare the groups. RESULTS: Thirty-eight patients in Group P and 17 patients in Group N met inclusion criteria. The average follow-up was 2.6 years. Group P was younger than Group N by an average of 9.6 months (P=0.04), but the MOS for skeletal maturity was not different between groups (P=0.15). Group P had significantly diminished neck length (P=0.008) and significantly increased relative trochanteric overgrowth as evidenced by increased trochanteric femoral head overlap percentage (P<0.001), but there was no difference between groups in neck shaft angle and neck width. No patient in Group N developed femoral head deformity (all Type 1). In Group P, 14 patients (37%) developed Types 2 and 3 deformity. In patients with MOS 16 in Group P, 60% (3/5) developed Type 2 deformity and 40% (2/5) developed Type 3 deformity. In patients with MOS 17 in Group P, 45% (5/11) had Type 2 deformity. CONCLUSIONS: Skeletally immature patients with an MOS of 16 and 17 are at high risk for developing the triad of relative trochanteric overgrowth, coxa breva, and femoral head asphericity with prophylactic threaded screw fixation for SCFE. When prophylactic surgery is indicated, consideration should be given to growth friendly fixation strategies to avoid iatrogenic proximal femoral deformity. LEVELS OF EVIDENCE: Level III-therapeutic retrospective comparative study.

Salinity pulses interact with seasonal dry-down to increase ecosystem carbon loss in marshes of the Florida Everglades.

Coastal wetlands are globally important sinks of organic carbon (C). However, to what extent wetland C cycling will be affected by accelerated sea-level rise (SLR) and saltwater intrusion is unknown, especially in coastal peat marshes where water flow is highly managed. Our objective was to determine how the ecosystem C balance in coastal peat marshes is influenced by elevated salinity. For two years, we made monthly in situ manipulations of elevated salinity in freshwater (FW) and brackish water (BW) sites within Everglades National Park, Florida, USA. Salinity pulses interacted with marsh-specific variability in seasonal hydroperiods whereby effects of elevated pulsed salinity on gross ecosystem productivity (GEP), ecosystem respiration (ER), and net ecosystem productivity (NEP) were dependent on marsh inundation level. We found little effect of elevated salinity on C cycling when both marsh sites were inundated, but when water levels receded below the soil surface, the BW marsh shifted from a C sink to a C source. During these exposed periods, we observed an approximately threefold increase in CO2 efflux from the marsh as a result of elevated salinity. Initially, elevated salinity pulses did not affect Cladium jamaicense biomass, but aboveground biomass began to be significantly decreased in the saltwater amended plots after two years of exposure at the BW site. We found a 65% (FW) and 72% (BW) reduction in live root biomass in the soil after two years of exposure to elevated salinity pulses. Regardless of salinity treatment, the FW site was C neutral while the BW site was a strong C source (-334 to -454 g C·m-2 ·yr-1 ), particularly during dry-down events. A loss of live roots coupled with annual net CO2 losses as marshes transition from FW to BW likely contributes to the collapse of peat soils observed in the coastal Everglades. As SLR increases the rate of saltwater intrusion into coastal wetlands globally, understanding how water management influences C gains and losses from these systems is crucial. Under current Everglades' water management, drought lengthens marsh dry-down periods, which, coupled with saltwater intrusion, accelerates CO2 loss from the marsh.

A Clinical Librarian Embedded in Medical Education: Patient-Centered Encounters for Preclinical Medical Students.

Adding patient encounters and simulation to the preclinical years of medical school is becoming increasingly popular. This article describes the creation of active learning opportunities by a clinical librarian that are aimed at training preclinical students through the use of simulated patient scenarios. Scenarios for second-year students walk them through the evidence-based resources needed in clinical years and beyond through a standardized patient encounter. Scenarios for first-year students involve role-play of cases where the patient and physician bring contrasting ideas to the outpatient interaction. All scenarios are carried out under the guidance of a clinician and librarian.

The Relationship Between Hip Strength and the Y Balance Test.

CONTEXT: The Y Balance Test was developed as a test of dynamic postural control and has been shown to be predictive of lower-extremity injury. However, the relationship between hip strength and performance on the Y Balance Test has not been fully elucidated. OBJECTIVE: The goal of this study was to identify the relationship between components of isometric hip strength and the Y Balance Test, to provide clinicians better guidance as to specific areas of muscle performance to address in the event of poor performance on the Y Balance Test. DESIGN: Laboratory study. SETTING: Biomechanics laboratory. PARTICIPANTS: A total of 73 healthy participants (40 males and 33 females) volunteered for this study. INTERVENTION: None. MAIN OUTCOME MEASURES: Participants completed the Y Balance Test on the right leg. The authors then measured peak isometric torque in hip external rotation, abduction, and extension. Correlations were calculated between torque measurements, normalized for mass and Y Balance Test performance. Significant relationships were used in linear regression models to determine which variables were predictive of the Y Balance Test performance. RESULTS: The authors found significant positive correlations between Y Balance Test performance and hip abduction strength. They also found correlations between the Y Balance Test and hip extension and external rotation strengths. Linear regression analysis showed hip abduction to be the only significant predictor of Y Balance performance. CONCLUSIONS: The authors found the strongest association between the Y Balance Test and hip abduction strength. They also showed smaller but significant associations with hip extension and external rotation strength. When entered into a linear regression analysis, hip abduction strength was the only significant predictor of Y Balance performance. Using this information, practitioners should look to hip abduction strength when patients exhibit deficits in the Y Balance Test.

Noncovalent Surface Modification of Cellulose Nanopapers by Adsorption of Polymers from Aprotic Solvents.

Basic adsorption of hydrophobic polymers from aprotic solvents was introduced as a platform technology to modify exclusively the surfaces of cellulose nanopapers. Dynamic vapor sorption demonstrated that the water vapor uptake ability of the nanopapers remained unperturbed, despite strong repellency to liquid water caused by the adsorbed hydrophobic polymer on the surface. This was enabled by the fact that the aprotic solvents used for adsorption did not swell the nanopaper unlike water that is generally applied as the adsorption medium in such systems. As case examples, the adsorptions of polystyrene (PS) and poly(trifluoroethylene) (PF3E) were followed by X-ray photoelectron spectroscopy and water contact angle measurements, backed up with morphological analysis by atomic force microscopy. The resulting nanopapers are useful in applications like moisture buffers where repellence to liquid water and ability for moisture sorption are desired qualities.

Response of gaseous carbon emissions to low-level salinity increase in tidal marsh ecosystem of the Min River estuary, southeastern China.

Although estuarine tidal marshes are important contributors to the emission of greenhouse gases into the atmosphere, the relationship between carbon dioxide (CO2), methane (CH4) emission, and environmental factors, with respect to estuarine marshes, has not been clarified thoroughly. This study investigated the crucial factors controlling the emission of CO2 and CH4 from a freshwater marsh and a brackish marsh located in a subtropical estuary in southeastern China, as well as their magnitude. The duration of the study period was November 2013 to October 2014. Relevant to both the field and incubation experiments, the CO2 and CH4 emissions from the two marshes showed pronounced seasonal variations. The CO2 and CH4 emissions from both marshes demonstrated significant positive correlations with the air/soil temperature (p<0.01), but negative correlations with the soil electrical conductivity and the pore water/tide water Cl- and SO42- (p<0.01). The results indicate no significant difference in the CO2 emissions between the freshwater and brackish marshes in the subtropical estuary, whereas there was a difference in the CH4 emissions between the two sites (p<0.01). Although future sea-level rise and saltwater intrusion could reduce the CH4 emissions from the estuarine freshwater marshes, these factors had little effect on the CO2 emissions with respect to an increase in salinity of less than 5‰. The findings of this study could have important implications for estimating the global warming contributions of estuarine marshes along differing salinity gradients.

The population genetics of drug resistance evolution in natural populations of viral, bacterial and eukaryotic pathogens.

Drug resistance is a costly consequence of pathogen evolution and a major concern in public health. In this review, we show how population genetics can be used to study the evolution of drug resistance and also how drug resistance evolution is informative as an evolutionary model system. We highlight five examples from diverse organisms with particular focus on: (i) identifying drug resistance loci in the malaria parasite Plasmodium falciparum using the genomic signatures of selective sweeps, (ii) determining the role of epistasis in drug resistance evolution in influenza, (iii) quantifying the role of standing genetic variation in the evolution of drug resistance in HIV, (iv) using drug resistance mutations to study clonal interference dynamics in tuberculosis and (v) analysing the population structure of the core and accessory genome of Staphylococcus aureus to understand the spread of methicillin resistance. Throughout this review, we discuss the uses of sequence data and population genetic theory in studying the evolution of drug resistance.