Exploring medical students' perspectives of physician leadership.

BACKGROUND: Leadership has been recognized as an important competency in medicine. Nevertheless, leadership curricula for Canadian medical students lacks standardization and may not be informed by medical students' perspectives of physician leadership. The purpose of this study was to elicit these perspectives on physician leadership. METHODS: The present study utilized semi-structured interviews to ascertain the views of medical student participants, including students in their first, second and third years of medical school, on physician leadership. Interview questions were based on 'the 3-C model' of physician leadership, which includes three aspects of leadership, namely character, competence and commitment. The interviews were audio-recorded, transcribed and then coded using thematic analysis. RESULTS: The medical students of this study provided rich examples of resident and staff physicians demonstrating effective and ineffective leadership. The participants identified the importance of character to effective physician leadership, but some participants also described a feeling of disconnect with the relevance of character at their stage of training. When discussing physician competence, medical students described the importance of both medical expertise and transferable skills. Lastly, the leadership aspect of commitment was identified as being relevant, but medical students cautioned against the potential for physician burnout. The medical student participants' suggestions for improved leadership development included increased experiences with examples of physician leadership, opportunities to engage in leadership and participation in reflection exercises. CONCLUSIONS: Overall, the study participants demonstrated an appreciation for three aspects of leadership; character, competence and commitment. Furthermore, they also provided recommendations for the future design of medical leadership curricula.

Perspectives on physician leadership: The role of character-based leadership in medicine.

INTRODUCTION: Physician leadership is multifaceted, but leadership training in medicine often is not. Leadership education and training for physicians are rarely grounded in conceptual leadership frameworks and suffer from a primary focus on cognitive leadership domains. Character-based leadership is a conceptual leadership framework that moves beyond cognitive competencies and articulates dimensions of character that promote effective leadership. The purpose of this study was to explore the relevance of character-based leadership in the medical context. METHODS: This qualitative descriptive study used semi-structured interviews to explore health care professionals' perceptions of character in relation to effective leadership in medicine. All interviews were audiorecorded and transcribed. Consistent with descriptive qualitative inquiry, a qualitative latent content analysis was used. Simultaneous data collection and analysis incorporating character-based leadership as a theoretical framework was used to help organise the analysis of the data. The researchers met regularly to clarify coding structures and categorise codes until sufficiency was reached. RESULTS: Twenty-six individuals (12 doctors, 5 nurses, 2 social workers, 2 directors and a pharmacist, dietician, coordinator, administrator and unit clerk) participated. Character-based leadership resonated with participants; they deemed character essential for effective physician leadership. Participants reflected on different character dimensions they attributed to an effective physician leader, in particular, collaboration, humility and humanity. They shared examples of working in interdisciplinary health care teams to illustrate these in practice. Moreover, participants believed that effective physician leaders need not be in a positional leadership role and asserted that physicians who demonstrate character stand out as leaders regardless of their career stage. DISCUSSION: Our findings suggest a role for a character-based leadership framework in medical education. Participants recognised the execution of character in everyday practice, associated character with effective leadership and understood leadership in dispositional rather than positional terms. These findings provide important insights for expanding and enhancing existing leadership training interventions.

Allopurinol hypersensitivity syndrome Raising awareness of an uncommon but potentially serious adverse event among kidney stone patients.

Allopurinol is a commonly prescribed agent in the urologic population for the prevention of urinary stones. Although generally well-tolerated, several serious potential side effects can occur with its use. Allopurinol hypersensitivity syndrome (AHS), in particular, is a relatively rare but potentially life-threatening complication. With the observed increase in urinary stone disease, especially those of uric acid composition, it is likely that the use of allopurinol will increase. Urologists play an important role in the assessment and medical management of patients with urinary stones, thus a greater awareness of the potential adverse events associated with allopurinol use, especially AHS, is important, as well as strategies that can minimize such risks. Herein, we review the potential adverse effects of allopurinol. In addition, the results of a comprehensive review of the current literature on AHS will be presented, highlighting those patients at highest risk, reviewing the genetic susceptibility testing currently available, and providing guidance on best practices when allopurinol therapy is being considered.

The 4C's of influence framework: fostering leadership development through character, competence, connection and culture.

PURPOSE: The purpose of this paper is to describe the 4C's of Infuence framework and it's application to medicine and medical education. Leadership development is increasingly recognised as an integral physician skill. Competence, character, connection and culture are critical for effective influence and leadership. The theoretical framework, "The 4C's of Influence", integrates these four key dimensions of leadership and prioritises their longitudinal development, across the medical education learning continuum. DESIGN/METHODOLOGY/APPROACH: Using a clinical case-based illustrative model approach, the authors provide a practical, theoretical framework to prepare physicians and medical learners to be engaging influencers and leaders in the health-care system. FINDINGS: As leadership requires foundational skills and knowledge, a leader must be competent to best exert positive influence. Character-based leadership stresses development of, and commitment to, values and principles, in the face of everyday situational pressures. If competence confers the ability to do the right thing, character is the will to do it consistently. Leaders must value and build relationships, fostering connection. Building coalitions with diverse networks ensures different perspectives are integrated and valued. Connected leadership describes leaders who are inspirational, authentic, devolve decision-making, are explorers and foster high levels of engagement. To create a thriving, learning environment, culture must bring everything together, or will become the greatest barrier. ORIGINALITY/VALUE: The framework is novel in applying concepts developed outside of medicine to the medical education context. The approach can be applied across the medical education continuum, building on existing frameworks which focus primarily on what competencies need to be taught. The 4C's is a comprehensive framework for practically teaching the leadership for health care today.

An Approach to Leadership Development and Patient Safety and Quality Improvement Education in the Context of Professional Identity Formation in Pre-Clinical Medical Students.

Objectives: Leadership and patient safety and quality improvement (PSQI) are recognized as essential parts of a physician's role and identity, which are important for residency training. Providing adequate opportunities for undergraduate medical students to learn skills related to these areas, and their importance, is challenging. Methods: The Western University Professional Identity Course (WUPIC) was introduced to develop leadership and PSQI skills in second-year medical students while also aiming to instill these topics into their identities. The experiential learning portion was a series of student-led and physician-mentored PSQI projects in clinical settings that synthesized leadership and PSQI principles. Course evaluation was done through pre/post-student surveys and physician mentor semi-structured interviews. Results: A total of 108 of 188 medical students (57.4%), and 11 mentors (20.7%), participated in the course evaluation. Student surveys and mentor interviews illustrated improved student ability to work in teams, self-lead, and engage in systems-level thinking through the course. Students improved their PSQI knowledge and comfort levels while also appreciating its importance. Conclusion: The findings from our study suggest that undergraduate medical students can be provided with an enriching leadership and PSQI experience through the implementation of faculty-mentored but student-led groups at the core of the curricular intervention. As students enter their clinical years, their first-hand PSQI experience will serve them well in increasing their capacity and confidence to take on leadership roles.

Reducing the risk of denosumab-induced hypocalcemia in patients with advanced chronic kidney disease: a quality improvement initiative.

Denosumab can improve bone health in advanced kidney disease (CKD) but is associated with hypocalcemia. We created a clinical care pathway focused on the safe provision of denosumab in advanced CKD that reduced the risk of hypocalcemia by 37% at our hospital. Similar pathways could be adopted and tested in other centers. PURPOSE: There is an increased risk of hypocalcemia with denosumab in advanced chronic kidney disease (CKD). We aimed to reduce the proportion of patients with advanced CKD who experienced denosumab-induced hypocalcemia at our center. METHODS: We conducted a quality improvement (QI) project of patients with CKD stage 3b or less (i.e., estimated glomerular filtration rate <45 mL/min/1.73m2 including dialysis) who were part of the Osteoporosis and Bone Disease Program at St. Joseph's Health Care London (Canada) between December 2020 and January 2023. Our intervention was a clinical care pathway which optimized CKD mineral and bone disorder (CKD-MBD) and 25-hydroxyvitamin levels; provided calcium and vitamin D prophylaxis; promoted multidisciplinary communication between bone and kidney specialists; and carefully monitored calcium post-denosumab injection. Our primary outcome measure was the proportion of patients with hypocalcemia (defined by albumin-corrected serum calcium <1.9mmol/L) at 60 days. Process measures included the appropriate provision of calcium and vitamin D prophylaxis. Balance measures included the development of hypercalcemia and hyperphosphatemia following prophylaxis. We used plan-do-see-act cycles to study four tests of change and presented results using descriptive statistics and run charts. RESULTS: There were 6 patients with advanced CKD treated with denosumab prior to the implementation of our care pathway (March 2015-October 2020; 83% receiving dialysis). At the time of their denosumab injection, 83% were using 500-1000 mg of calcium, and 83% used 1000-2000 IU of vitamin D3. Fifty percent developed denosumab-induced hypocalcemia. Following the implementation of our care pathway, 15 patients (40% receiving dialysis) were treated with denosumab. Ninety-three percent received calcium at a daily dose of 350 to 2250 mg and 87% received 1000-2000 IU of vitamin D3. Thirteen percent developed denosumab-induced hypocalcemia. There was no hypercalcemia or hyperphosphatemia. CONCLUSIONS: A clinical care pathway focused on the safe provision of denosumab in advanced CKD reduced the risk of hypocalcemia in patients treated in our hospital. Similar pathways could be adopted and tested in other centers.

In focus: perplexing increase of urinary stone disease in children, adolescent and young adult women and its economic impact.

Background: Urinary stone disease (USD) historically has affected older men, but studies suggest recent increases in women, leading to a near identical sex incidence ratio. USD incidence has doubled every 10 years, with disproportionate increases amongst children, adolescent, and young adult (AYA) women. USD stone composition in women is frequently apatite (calcium phosphate), which forms in a higher urine pH, low urinary citrate, and an abundance of urinary uric acid, while men produce more calcium oxalate stones. The reasons for this epidemiological trend are unknown. Methods: This perspective presents the extent of USD with data from a Canadian Province and a North American institution, explanations for these findings and offers potential solutions to decrease this trend. We describe the economic impact of USD. Findings: There was a significant increase of 46% in overall surgical interventions for USD in Ontario. The incidence rose from 47.0/100,000 in 2002 to 68.7/100,000 population in 2016. In a single United States institution, the overall USD annual unique patient count rose from 10,612 to 17,706 from 2015 to 2019, and the proportion of women with USD was much higher than expected. In the 10-17-year-old patients, 50.1% were girls; with 57.5% in the 18-34 age group and 53.6% in the 35-44 age group. The roles of obesity, diet, hormones, environmental factors, infections, and antibiotics, as well as the economic impact, are discussed. Interpretation: We confirm the significant increase in USD among women. We offer potential explanations for this sex disparity, including microbiological and pathophysiological aspects. We also outline innovative solutions - that may require steps beyond typical preventive and treatment recommendations.

Creep-dilatancy development at a transform plate boundary.

How tectonic plates slip slowly and episodically along their boundaries, is a major, open question in earthquake science. Here, we use offshore in-situ sediment pore-pressure acquired in the proximity of the active offshore Main Marmara Fault and onshore geodetic time-series data set from a single GPS station to demonstrate the pore-pressure/deformation coupling during a 10-month slow-slip event. We show that pore pressure fluctuations are the expression of hydro-mechanical process affecting the deep seismogenic zone and indicate that small disturbances in geodetic data may have important meaning in terms of transient deformations. These results have major implications in understanding the spatial impact of slow-slip processes and their role in earthquake cycles. We demonstrate that piezometers measuring along a transform fault can help define the time scale regulating the coupling between slow-slip events and earthquake nucleation process.

Validity of administrative database coding for kidney disease: a systematic review.

BACKGROUND: Information in health administrative databases increasingly guides renal care and policy. STUDY DESIGN: Systematic review of observational studies. SETTING & POPULATION: Studies describing the validity of codes for acute kidney injury (AKI) and chronic kidney disease (CKD) in administrative databases operating in any jurisdiction. SELECTION CRITERIA: After searching 13 medical databases, we included observational studies published from database inception though June 2009 that validated renal diagnostic and procedural codes for AKI or CKD against a reference standard. INDEX TESTS: Renal diagnostic or procedural administrative data codes. REFERENCE TESTS: Patient chart review, laboratory values, or data from a high-quality patient registry. RESULTS: 25 studies of 13 databases in 4 countries were included. Validation of diagnostic and procedural codes for AKI was present in 9 studies, and validation for CKD was present in 19 studies. Sensitivity varied across studies and generally was poor (AKI median, 29%; range, 15%-81%; CKD median, 41%; range, 3%-88%). Positive predictive values often were reasonable, but results also were variable (AKI median, 67%; range, 15%-96%; CKD median, 78%; range, 29%-100%). Defining AKI and CKD by only the use of dialysis generally resulted in better code validity. The study characteristic associated with sensitivity in multivariable meta-regression was whether the reference standard used laboratory values (P < 0.001); sensitivity was 39% lower when laboratory values were used (95% CI, 23%-56%). LIMITATIONS: Missing data in primary studies limited some of the analyses that could be done. CONCLUSIONS: Administrative database analyses have utility, but must be conducted and interpreted judiciously to avoid bias arising from poor code validity.

Denosumab in chronic kidney disease: a narrative review of treatment efficacy and safety.

People with chronic kidney disease (CKD) are at high risk of bone fractures. In this review, we summarize the complexity of fracture prevention in CKD, describe the usefulness of a medication called denosumab, and review its safety in this population. Our article will help doctors manage brittle bones in CKD and encourage researchers to conduct more studies to improve bone health in CKD. PURPOSE: Patients with CKD are at increased risk of fragility fractures and associated consequences. We discuss the complexity of fracture prevention in CKD, summarize the efficacy and safety of denosumab, and provide an approach to denosumab-induced hypocalcemia. METHODS: Using predefined terms, we searched PubMed, MEDLINE, and Google Scholar for studies on fracture prevention in CKD and the efficacy and safety of denosumab. We included observational studies, randomized controlled trials (RCTs), meta-analyses, evidence-based reviews, and clinical practice guidelines. RESULTS: The diagnosis of osteoporosis and prevention of related fragility fractures is complex in CKD, particularly in those with advanced and end-staged kidney disease (ESKD). Prior to initiating denosumab, it is important to assess for and optimize CKD-mineral and bone disorders (CKD-MBD). In observational studies and small RCTs, denosumab has been shown to improve bone mineral density and reduce bone turnover in CKD, but there have been no studies focused upon its fracture efficacy. Denosumab-induced hypocalcemia has also been reported, which disproportionately impacts those with ESKD. Risk factors for hypocalcemia with denosumab use in CKD include lower baseline serum calcium and 25 hydroxyvitamin D and both low and high bone turnover. Choosing the "right patient" for denosumab, supplementing with calcium and vitamin D, adjusting calcium dialysate, and close clinical monitoring are essential if considering this drug. CONCLUSION: With optimization of CKD-MBD, calcium and vitamin D supplementation, and close monitoring, denosumab can be considered in CKD. There are however opportunities to better understand its fracture efficacy and safety in an RCT setting.

Impact of tides and sea-level on deep-sea Arctic methane emissions.

Sub-sea Arctic methane and gas hydrate reservoirs are expected to be severely impacted by ocean temperature increase and sea-level rise. Our understanding of the gas emission phenomenon in the Arctic is however partial, especially in deep environments where the access is difficult and hydro-acoustic surveys are sporadic. Here, we report on the first continuous pore-pressure and temperature measurements over 4 days in shallow sediments along the west-Svalbard margin. Our data from sites where gas emissions have not been previously identified in hydro-acoustic profiles show that tides significantly affect the intensity and periodicity of gas emissions. These observations imply that the quantification of present-day gas emissions in the Arctic may be underestimated. High tides, however, seem to influence gas emissions by reducing their height and volume. Hence, the question remains as to whether sea-level rise may partially counterbalance the potential threat of submarine gas emissions caused by a warmer Arctic Ocean.

Purification and physicochemical characterization of two galactose-specific isolectins from the seeds of Trichosanthes cordata.

A galactose-specific lectin has been purified from the seeds of Trichosanthes cordata by affinity chromatography on crosslinked guar gum. The affinity-eluted lectin could be resolved into two isolectins, TCA-I and TCA-II by ion-exchange chromatography on DEAE cellulose. The molecular weights of the isolectins were determined as 59 and 52 kDa by SDS-PAGE. TCA-I is a heterodimer in which the two subunits with masses of 32 and 27 kDa, are covalently connected by disulfide bonds. TCA-I and TCA-II are glycoproteins with 6.2% and 6.8% covalently bound neutral sugar, respectively. CD spectroscopic studies indicate that the two isolectins are very similar in secondary structure and contain about 8 to 10% alpha-helix, 37-38% beta-sheet, 20% beta-turns, and 32-33% unordered structures. These isolectins have similar carbohydrate specificities as revealed by hemagglutination-inhibition assays. Carbohydrate specificity, subunit size and composition, and secondary structure of TCA isolectins suggest close similarity to type-II ribosome inactivating proteins. The agglutination activity of TCA-I was found to be highest in the pH range 7.0-8.0. The lectin activity was unaffected between 0 and 40 degrees C, but decreased dramatically above 40 degrees C. Association constant for the interaction of TCA-I with lactose was determined by monitoring ligand-induced changes in the protein intrinsic fluorescence characteristics as 7.42 x 10(3) M(-1) at 25 degrees C. The exposure and accessibility of the tryptophan residues of TCA-I and the effect of ligand binding on them have been probed by quenching studies employing neutral and ionic quenchers.

Fluorescence studies on the interaction of hydrophobic ligands with Momordica charantia (bitter gourd) seed lectin.

The interaction of Momordica charantia (bitter gourd) seed lectin (MCL) with several nucleic acid bases has been investigated by monitoring changes induced in the protein fluorescence by ligand binding. Values of the binding constant, K(a) were obtained as 1.1 x 10(4), 1.56 x 10(4) and 2.2 x 10(3) M(-1) for adenine, cytosine and uracil, respectively. In addition, binding of 8-anilinonaphthalene 1-sulfonate (ANS) with MCL was investigated by fluorescence spectroscopy. Interaction with MCL at low pH results in a large enhancement of the fluorescence intensity of ANS with a concomitant blue shift in the emission lambda(max), whereas at neutral and basic pH changes in both fluorescence intensity and emission maximum were very small, clearly suggesting that the MCL-ANS interaction is stronger at lower pH values. When excited at 295 nm in the presence of ANS, the protein fluorescence decreased with a concomitant increase in the emission intensity of ANS, suggesting resonance energy transfer from the tryptophan residues of MCL to ANS. Gel filtration profiles of MCL at pH values 2.0 and 7.4 are similar indicating that the tetrameric nature of MCL is retained even at low pH. Addition of lactose or adenine to MCL-ANS mixture did not alter the change in ANS fluorescence suggesting that lactose, adenine and ANS bind to MCL at independent and non-interacting sites. These results are relevant to understanding the functional role of MCL in the parent tissue.

Leadership Development in Postgraduate Medical Education: A Systematic Review of the Literature.

PURPOSE: To evaluate and interpret evidence relevant to leadership curricula in postgraduate medical education (PGME) to better understand leadership development in residency training. METHOD: The authors conducted a systematic review of peer-reviewed, English-language articles from four databases published between 1980 and May 2, 2017 that describe specific interventions aimed at leadership development. They characterized the educational setting, curricular format, learner level, instructor type, pedagogical methods, conceptual leadership framework (including intervention domain), and evaluation outcomes. They used Kirkpatrick effectiveness scores and Best Evidence in Medical Education (BEME) Quality of Evidence scores to assess the quality of the interventions. RESULTS: Twenty-one articles met inclusion criteria. The classroom setting was the most common educational setting (described in 17 articles). Most curricula (described in 13 articles) were isolated, with all curricula ranging from three hours to five years. The most common instructor type was clinical faculty (13 articles). The most commonly used pedagogical method was small group/discussion, followed by didactic teaching (described in, respectively, 15 and 14 articles). Study authors evaluated both pre/post surveys of participant perceptions (n = 7) and just postintervention surveys (n = 10). The average Kirkpatrick Effectiveness score was 1.0. The average BEME Quality of Evidence score was 2. CONCLUSIONS: The results revealed that interventions for developing leadership during PGME lack grounding conceptual leadership frameworks, provide poor evaluation outcomes, and focus primarily on cognitive leadership domains. Medical educators should design future leadership interventions grounded in established conceptual frameworks and pursue a comprehensive approach that includes character development and emotional intelligence.

Association between proton pump inhibitors and respiratory infections: a systematic review and meta-analysis of clinical trials.

BACKGROUND: Proton pump inhibitors (PPIs) have become the mainstay of treatment for and prevention of many serious gastrointestinal diseases. Laboratory and clinical evidence suggests that the increase in gastric pH caused by PPIs may be linked to increased bacterial colonization of the stomach and may predispose patients to an increased risk for respiratory infections. OBJECTIVE: To examine the association between PPI treatment and respiratory infections. METHODS: A literature search was conducted using PubMed, MEDLINE and Cochrane databases of randomized, placebo-controlled trials evaluating the efficacy of PPIs. Studies that listed and quantified the specific adverse events of 'respiratory infection' or 'upper respiratory infection' (or equivalent), and compared their rates between PPIs and placebo were included. The chi(2) analysis was used to calculate the significance of association in individual studies and a meta-analysis of the selected studies was performed. RESULTS: Of 7457 studies initially identified and 70 relevant randomized, controlled trials (RCTs) selected, seven studies met the inclusion criteria. A total of 16 comparisons for chi(2) analysis were possible given the multiple dosage arms used in several studies. PPIs included in the studies were esomeprazole, rabeprazole, pantoprazole and omeprazole. More than one-half of the studies showed a trend toward an association between PPI use and respiratory infections, although the majority of the studies failed to show a significant correlation. A single study using high-dose esomeprazole (40 mg) showed a significant association -4.3% rate of respiratory infections in the active group compared with 0% in the placebo group (P<0.05). Meta-analysis showed a trend toward an association between PPIs and respiratory infections, although it failed to reach significance (OR 1.42, 95% CI 0.86 to 2.35; P=0.17). CONCLUSION: Although a trend was evident in both a chi(2) analysis of individual studies and a meta-analysis, the present review and meta-analysis failed to show a conclusive association between PPIs and respiratory infections. Very few RCTs actively sought out respiratory infections, which excluded the majority of RCTs identified. A well-structured, placebo-controlled prospective study would be needed to determine whether a true association between PPIs and respiratory infections exists.

Freshwater lake to salt-water sea causing widespread hydrate dissociation in the Black Sea.

Gas hydrates, a solid established by water and gas molecules, are widespread along the continental margins of the world. Their dynamics have mainly been regarded through the lens of temperature-pressure conditions. A fluctuation in one of these parameters may cause destabilization of gas hydrate-bearing sediments below the seafloor with implications in ocean acidification and eventually in global warming. Here we show throughout an example of the Black Sea, the world's most isolated sea, evidence that extensive gas hydrate dissociation may occur in the future due to recent salinity changes of the sea water. Recent and forthcoming salt diffusion within the sediment will destabilize gas hydrates by reducing the extension and thickness of their thermodynamic stability zone in a region covering at least 2800 square kilometers which focus seepages at the observed sites. We suspect this process to occur in other world regions (e.g., Caspian Sea, Sea of Marmara).

Tryptophan environment, secondary structure and thermal unfolding of the galactose-specific seed lectin from Dolichos lablab: fluorescence and circular dichroism spectroscopic studies.

Fluorescence and circular dichroism spectroscopic studies were carried out on the galactose-specific lectin from Dolichos lablab seeds (DLL-II). The microenvironment of the tryptophan residues in the lectin under native and denaturing conditions were investigated by quenching of the intrinsic fluorescence of the protein by a neutral quencher (acrylamide), an anionic quencher (iodide ion) and a cationic quencher (cesium ion). The results obtained indicate that the tryptophan residues of DLL-II are largely buried in the hydrophobic core of the protein matrix, with positively charged side chains residing close to at least some of the tryptophan residues under the experimental conditions. Analysis of the far UV CD spectrum of DLL-II revealed that the secondary structure of the lectin consists of 57% alpha-helix, 21% beta-sheet, 7% beta-turns and 15% unordered structures. Carbohydrate binding did not significantly alter the secondary and tertiary structures of the lectin. Thermal unfolding of DLL-II, investigated by monitoring CD signals, showed a sharp transition around 75 degrees C both in the far UV region (205 nm) and the near UV region (289 nm), which shifted to ca. 77-78 degrees C in the presence of 0.1 M methyl-beta-D-galactopyranoside, indicating that ligand binding leads to a moderate stabilization of the lectin structure.

New insights into the transport processes controlling the sulfate-methane-transition-zone near methane vents.

Over the past years, several studies have raised concerns about the possible interactions between methane hydrate decomposition and external change. To carry out such an investigation, it is essential to characterize the baseline dynamics of gas hydrate systems related to natural geological and sedimentary processes. This is usually treated through the analysis of sulfate-reduction coupled to anaerobic oxidation of methane (AOM). Here, we model sulfate reduction coupled with AOM as a two-dimensional (2D) problem including, advective and diffusive transport. This is applied to a case study from a deep-water site off Nigeria's coast where lateral methane advection through turbidite layers was suspected. We show by analyzing the acquired data in combination with computational modeling that a two-dimensional approach is able to accurately describe the recent past dynamics of such a complex natural system. Our results show that the sulfate-methane-transition-zone (SMTZ) is not a vertical barrier for dissolved sulfate and methane. We also show that such a modeling is able to assess short timescale variations in the order of decades to centuries.

Fluorescence quenching and time-resolved fluorescence studies on Trichosanthes dioica seed lectin.

Fluorescence quenching and time-resolved fluorescence studies have been carried out on the Trichosanthes dioica seed lectin (TDSL). The emission lambdamax of native TDSL, seen at 328nm, shifts to 343nm upon denaturation with 6M guanidinium chloride. Quenching titrations were performed with neutral (acrylamide and succinimide) and ionic (I(-) and Cs(+)) quenchers in order to probe the exposure and accessibility of tryptophan residues of the protein. Maximum quenching was observed with acrylamide, followed by succinimide, iodide and Cs(+). Dramatic increase in the extent of quenching and other quenching parameters by all the quenchers were observed upon denaturation of TDSL, suggesting that all the tryptophan residues in native TDSL are buried in the hydrophobic core of the protein. Increase in the extent of quenching upon denaturation of TDSL was maximum with I(-) and minimum with Cs(+), suggesting the presence of positively charged residue(s), near at least one tryptophan residue. Addition of saccharide ligands such as methyl-beta-d-galactopyranoside and lactose led to a small, but reproducible decrease in the fluorescence intensity of the lectin. The presence of lactose provided a partial protection against quenching by I(-), Cs(+) and succinimide, but not acrylamide. In time-resolved fluorescence measurements the fluorescence decay curves could be best fitted to biexponential patterns with lifetimes of 4.09 and 1.53ns for native lectin, 3.40 and 1.65ns for the lectin in presence of 0.1M lactose and 3.50 and 1.40ns for denatured lectin.