Enhancing productivity and sustainability of ravine lands through horti-silviculture and soil moisture conservation: A pathway to land degradation neutrality.

Ravine lands are the worst type of land degradation affecting soil quality and biodiversity. Crop production in such lands is impossible without adopting proper conservation measures. In-situ moisture conservation techniques could play an instrumental role in restoring ravine lands by improving soil moisture. We hypothesized that restoring ravine land through a combination of tree planting, fruit crop cultivation, and in-situ moisture conservation practice would result in significant improvements in productivity, profitability, and soil fertility. An experiment was conducted involving the combination of Malabar Neem (Melia dubia) and Dragon fruit (Hylocereus undatus) in conjunction with in-situ soil moisture conservation measures specifically involving half-moon structures (HM). The experiment was conducted under randomized block design (RBD) comprising eight treatments. These treatments include sole Melia cultivation (MD 3m × 3m), sole cultivation of dragon fruit (DF 3m × 3m), silviculture system (MDF-3m × 3m), horti-silviculture system with larger spacing (MDF-4m × 4m), sole Melia cultivation with in-situ moisture conservation (MDH-3m × 3m), sole Dragon fruit cultivation with in-situ moisture conservation (DFH-3m × 3m), horti-silviculture system of Melia and Dragon fruit with in-situ moisture conservation (MDFH-3m × 3m), and horti-silviculture system with larger spacing and in-situ moisture conservation (MDFH-4m × 4m). Each treatment was replicated thrice to evaluate their impact on productivity, profitability, soil fertility, and carbon sequestration for 8 years (2016-2023). The results revealed that the horti-silviculture system (MDFH-3 × 3 m) exhibited the highest total tree biomass and total carbon sequestration with an increase of 183.2% and 82.8% respectively, compared to sole Melia cultivation without HM and sole Melia with HM. Furthermore, sole Melia with HM augmented soil nutrients (N, P, K, and SOC) by 74.4%, 66.4%, 35.2%, and 78.3%, respectively, compared to control (no planting), with performance at par with MDFH-3 × 3 m. Similarly, sole Melia with HM enhanced SOC stock and SOC sequestration rate by 79.2% and 248% over control. However, it was found at par with MDFH-3 × 3 m. The horti-silviculture system (MDFH-3 × 3 m) consistently produced the highest fruit yield throughout the years surpassing other treatments. This treatment increased the average dragon fruit yield by 115.3% compared to sole dragon fruit without HM. Hence, the adoption of the horti-silviculture system (MDFH-3 × 3 m) could be a promising strategy for achieving enhanced environmental and economic benefits in ravine lands. Therefore, dragon fruit based horti-silviculture system (MDFH-3 × 3 m) could be recommended for restoration of ravine lands, improving land productivity, and mitigating impact of soil erosion particularly in Western India or similar agro-climatic regions of the world.

Factors associated with successful tobacco use cessation among teachers in Bihar state, India: a mixed-method study.

Although tobacco use is declining in several countries including India (dropping from 35% in 2009-10 to 29% 2016-17 among adults)-it still poses a huge burden on India, as the world's second largest consumer of tobacco products. In Bihar state, with a prevalence of 25%, the Bihar School Teachers Study (BSTS) successfully enlisted teachers as role models for encouraging quitting and changing social norms pertaining to tobacco. The study used a mixed-methods approach to identify factors associated with teachers' quitting. Qualitative data were collected through focus groups with teachers and school principals. Quantitative data were collected through a written survey administered to school personnel post-intervention. Key findings from focus groups were that teachers and principals quit using tobacco and promoted cessation because they wanted to model positive behaviors; specific information about tobacco's harms aided cessation; and the BSTS intervention facilitated a school environment that supported quitting. Survey results indicated teachers who reported knowing people who quit using tobacco in the prior year were far more likely to quit as were teachers who reported that their school's tobacco policy was completely enforced. The combination of qualitative and quantitative data yielded important insights with strong implications for future interventions.

Traumatic abdominal wall injuries: a review.

Traumatic abdominal wall injuries have been described in literature for over 100 years. These injuries involve abdominal wall from skin to the level of fascia. These are often associated with underlying visceral injuries. The diagnosis requires a high index of suspicion and is based on clinical examination and radiologic investigations. Management ranges from conservative management to complex abdominal wall reconstruction. In the following review we describe the incidence, clinical features, diagnosis, management and possible interventions for prevention of these injuries.

Mannose-binding lectin (+54) exon-1 gene polymorphism influence human immunodeficiency virus-1 susceptibility in North Indians.

Mannose-binding lectin (MBL) is a circulating pattern-recognition molecule involved in the innate immune system that mediates phagocytosis and activates complement by binding to carbohydrate motifs. MBL-2 allelic variants are associated with deficiencies in innate immunity and have been found to be correlated with human immunodeficiency virus (HIV) infection. The present study investigated the role of MBL-2 exon-1 gene polymorphism (A, B, C and D) in 180 HIV-1 seropositive (HSP) stratified on the basis of disease severity (stage I, II, III), 50 HIV-1 exposed seronegative (HES) and 305 HIV-1 seronegative (HSN) individuals as a possible factor in the susceptibility to HIV-1 infection and the influence on disease progression among North Indian individuals. In our population, gene frequencies of MBL-2 variants were 15%, 5% and 2% for B, C and D alleles, respectively. The frequency of A/O heterozygous genotype was higher (42.00%), mainly because of A/D in HES group compared with HSP (35.00%) and HSN (36.72%) group. Homozygous B/B genotype was more frequent in HSP (6.11%) group than in HSN (1.31%; P = 0.005; odds ratio (OR) = 4.898) and was significantly associated with fourfold risk of acquiring HIV-1 infection. Our findings indicate that homozygosity for the codon 54-allele associated with low MBL production in the exon-1 of the MBL-2 gene is associated with increased susceptibility to HIV-1 infection in the studied population.

Recent developments in membrane-based separations in biotechnology processes: review.

Membrane-based separations are the most ubiquitous unit operations in biotech processes. There are several key reasons for this. First, they can be used with a large variety of applications including clarification, concentration, buffer exchange, purification, and sterilization. Second, they are available in a variety of formats, such as depth filtration, ultrafiltration, diafiltration, nanofiltration, reverse osmosis, and microfiltration. Third, they are simple to operate and are generally robust toward normal variations in feed material and operating parameters. Fourth, membrane-based separations typically require lower capital cost when compared to other processing options. As a result of these advantages, a typical biotech process has anywhere from 10 to 20 membrane-based separation steps. In this article we review the major developments that have occurred on this topic with a focus on developments in the last 5 years.

Genetic Gains in Pearl Millet in India: Insights Into Historic Breeding Strategies and Future Perspective.

Pearl millet (Pennisetum glaucum R. Br.) is an important staple and nutritious food crop in the semiarid and arid ecologies of South Asia (SA) and Sub-Saharan Africa (SSA). In view of climate change, depleting water resources, and widespread malnutrition, there is a need to accelerate the rate of genetic gains in pearl millet productivity. This review discusses past strategies and future approaches to accelerate genetic gains to meet future demand. Pearl millet breeding in India has historically evolved very comprehensively from open-pollinated varieties development to hybrid breeding. Availability of stable cytoplasmic male sterility system with adequate restorers and strategic use of genetic resources from India and SSA laid the strong foundation of hybrid breeding. Genetic and cytoplasmic diversification of hybrid parental lines, periodic replacement of hybrids, and breeding disease-resistant and stress-tolerant cultivars have been areas of very high priority. As a result, an annual yield increase of 4% has been realized in the last three decades. There is considerable scope to further accelerate the efforts on hybrid breeding for drought-prone areas in SA and SSA. Heterotic grouping of hybrid parental lines is essential to sustain long-term genetic gains. Time is now ripe for mainstreaming of the nutritional traits improvement in pearl millet breeding programs. New opportunities are emerging to improve the efficiency and precision of breeding. Development and application of high-throughput genomic tools, speed breeding, and precision phenotyping protocols need to be intensified to exploit a huge wealth of native genetic variation available in pearl millet to accelerate the genetic gains.

Process analytical technology (PAT) for biopharmaceutical products: Part I. concepts and applications.

Process analytical technology (PAT) has been gaining momentum in the biotech community due to the potential for continuous real-time quality assurance resulting in improved operational control and compliance. In this two part series, we address PAT as it applies to processes that produce biotech therapeutic products. In the first part, we address evolution of the underlying concepts and applications in biopharmaceutical manufacturing. We also present a literature review of applications in the areas of upstream and downstream processing to illustrate how implementation of PAT can help realize advanced approaches to ensuring product quality in real time. In the second part, we will explore similar applications in the areas of drug product manufacturing, rapid microbiology, and chemometrics as well as evolution of PAT in biotech processing.

Process analytical technology (PAT) for biopharmaceutical products: Part II. Concepts and applications.

Implementing real-time product quality control meets one or both of the key goals outlined in FDA's PAT guidance: "variability is managed by the process" and "product quality attributes can be accurately and reliably predicted over the design space established for materials used, process parameters, manufacturing, environmental, and other conditions." The first part of the paper presented an overview of PAT concepts and applications in the areas of upstream and downstream processing. In this second part, we present principles and case studies to illustrate implementation of PAT for drug product manufacturing, rapid microbiology, and chemometrics. We further present our thoughts on how PAT will be applied to biotech processes going forward. The role of PAT as an enabling component of the Quality by Design framework is highlighted. Integration of PAT with the principles stated in the ICH Q8, Q9, and Q10 guidance documents is also discussed.

Process analytical technology (PAT) for biopharmaceutical products.

The "Pharmaceutical Current Good Manufacturing Practices (CGMPs) for the 21st Century--A Risk Based Approach" initiative announced by the FDA in August 2002 to improve and modernize pharmaceutical manufacturing facilitated adoption of process analytical technology (PAT) by the pharmaceutical industry. The potential for improved operational control and compliance resulting from continuous real-time quality assurance was highlighted as a likely benefit that would result from PAT implementation. A considerable amount of work has been done on this topic by academic and industrial contributors in the last decade. In this paper, we will start with a brief overview of evolution of PAT concepts and a review of their application in the wider pharmaceutical industry. The rest of the paper focuses on PAT applications for biotech processes with emphasis on developments in the last five years. It is our observation that while significant advances have been accomplished with regard to our ability to analyze/monitor key process and quality attributes in the biotech industry, much more needs to be done with regard to utilizing the collected data for subsequent control of the process, to achieve optimum yield and product quality. The latter is necessary to achieve the benefits that will result from PAT implementation.

Quality and effectiveness of counselling at antiretroviral therapy centres in India: capturing counsellor and beneficiary perspectives.

BACKGROUND: Ensuring the quality and effectiveness of counselling is imperative for enabling people living with HIV to cope with treatment adherence. Countrywide assessment of antiretroviral therapy (ART) centres was undertaken to assess the quality and effectiveness of counselling. The insights gained from the assessment are expected to build an improved understanding of the counselling aspect and contribute to informing decisions strengthening the counselling provided at ART centres. METHODS: Assessment of counselling at 357 ART centres entailed interviews with counsellors and beneficiaries using a structured questionnaire administered by trained technical experts. Two counsellors and five beneficiaries at each ART centre were interviewed to assess both the quality and effectiveness of counselling. Beneficiaries were selected from different risk groups to understand their varied concerns and experiences. RESULTS: During the assessment, 618 counsellors were interviewed (45% women); also, 1785 beneficiaries were interviewed, consisting of 892 (49.9%) men, 857 (48.1%) women and 36 (2.0%) transgender. Counsellors were found to be relatively well informed on topics pertaining to pre-ART, ART preparedness and positive healthy living, and the psychosocial support extended to patients. Counsellors surveyed were not aware of critical areas such as counselling of pregnant women (44.5%) , drug adherence (44.8%) and the use of information, education and communication material during counselling, and pill count. The majority of beneficiaries reported being informed on issues pertaining to retention; however, 30-40% of beneficiaries were not informed regarding the critical elements of adherence such as counselling on ART side effects (68.5%), pill count (62.8%) and information on access to social benefit schemes (25.7%). Factors such as client volume, the training of the counsellors and adequate space for counselling affected the quality of counselling. CONCLUSION: With concerted efforts in bridging the gaps in knowledge, infrastructure and information needs, India's national AIDS control programme (NACP) can enhance the counselling services at ART centres and improve the quality of services for patient retention.

Long-term outcome of combined trabeculotomy-trabeculectomy by a single surgeon in patients with primary congenital glaucoma.

PurposeAssess long-term outcome of combined trabeculotomy-trabeculectomy (CTT) in primary congenital glaucoma (PCG).MethodsData of PCG patients treated with CTT by a single surgeon between 1976 and 1993 were reviewed for reduction in intraocular pressure (IOP), visual acuities, surgical success rates, and need for repeat surgeries at last follow-up (FU). At the last FU, IOP<21 mm Hg without any topical antiglaucoma medication (TAM) was complete success and with 1-2 TAMs was qualified success. IOP reduction ≥30% without any TAM was modified complete success and with 1-2 TAMs was modified qualified success. IOP>21 mm Hg, IOP reduction <30%, or use of >2 TAM at last FU, or need for additional surgery was considered as failure.ResultsTwo hundred thirty eyes of 121 patients had been followed up for 21.5-38 years (mean 28.87±2.77 years). Eyes that were pthisical (3), had immeasurable IOP (2), or IOP<6 mm Hg (3) were excluded from the success analysis. At last FU, mean IOP reduction was 22.71±11.28 mm Hg and TAM score was 1.71 (0-4). Complete success was achieved in 14 (6.3%), modified complete success in 14 (6.3%), qualified success in 148 (66.7%), and modified qualified success in 140 (63.1%). Success probability was 95% till 25 years and 92, 90, 85, 79 and 68% at 26, 27, 28, 29, and 30 years, respectively. Severe visual impairment or functional blindness was found in only 13 (10.7%) patients.ConclusionCTT shows long-term success in PCG patients. All patients must be monitored for IOP control to avoid need for repeat surgeries.

New insights into anaplastic lymphoma kinase-positive nonsmall cell lung cancer.

BACKGROUND: A novel fusion gene of echinoderm microtubule-associated protein-like 4 (EML4) and anaplastic lymphoma kinase (ALK) has been identified in a subset of non-small-cell lung cancers (NSCLCs). Patients with the ALK-EML4 fusion gene demonstrate unique clinicopathological and physiological characteristics. Here we present an analysis of clinicopathological profile of patients of metastatic adenocarcinoma harboring the ALK-EML4 fusion gene and their response to targeted therapy in the form of crizotinib. METHODS: A retrospective analysis of advanced ALK positive NSCLC, who presented at this tertiary care hospital of armed forces from September 2014 to December 2016 was conducted. The primary goal was to evaluate demographic and clinicopathological profile of ALK positive advanced NSCLC. Detection of ALK fusion was done by IHC on formalin fixed paraffin embedded cell blocks. Out of 20 ALK positive patients, ten patients received upfront cytotoxic chemotherapy, and rest received crizotinib. Patients progressing on cytotoxic chemotherapy received crizotinib as subsequent therapy. RESULTS: Out of 270 patients of NSCLC, fifteen(7.4%) tested positive for ALK-EML4 fusion. Rate of positivity was higher in females(13.7%) than in males (5%). The correlation of the ALK-EML4 fusion gene and clinicopathological characteristics of NSCLC patients demonstrated a significant difference in smoking status, histological types, stage, & metastatic pattern. Median PFS with first line cytotoxic chemotherapy was 5.9 months. Median PFS with upfront crizotinib was not reached, but was significantly superior than cytotoxic chemotherapy. CONCLUSION: Our analysis indicated that ALK-EML4 positive NSCLC comprised a unique subgroup of adenocarcinomas with distinct clinicopathological characteristics. Incidence of ALK positivity was found to be higher in females and never smokers. These patients have distinct pathological and radiological characteristics. Crizotinib, whether used upfront or as subsequent therapy was found to be superior in PFS (not yet reached at the time of writing this article), and maintaining quality of life as compared to cytotoxic chemotherapy.

Assessment of quality of antiretroviral therapy services in India, 2014-2015.

Background: Following a decade of provision of free antiretroviral therapy (ART) in India, a nationwide assessment of ART services was conducted to review quality of care at ART centers. This paper presents the methods and defines replicable model of undertaking large scale assessments. Methods: During the period January 2014-March 2015, 357 ART centers were reviewed under four domains, namely, operations, technical, monitoring and evaluation (M&E), and logistics. Mixed methods, comprising of desk review and on-site facility assessment; random sample of records, interviews with both health-care staff and people living with HIV (PLHIV) were used. Grading for each of the domain was done on a scale of 5, with 1 (Very poor) being the lowest and 5 (Excellent) as highest. Results: 1720 health-care staff and 1762 beneficiaries were interviewed; 34 600 patient cards were reviewed. Of the 357 centers assessed 60, 169 and 128 scored Excellent, Average and Poor, respectively, in operations domain; 147, 176, 34 in Technical domain; 215, 115, 27 in M&E domain; 263, 71, 23 centers in logistics domain scored Excellent, Average and Poor, respectively. About 95% (1698/1785) of PLHIV were satisfied with the care provided at ART centers. Conclusion: The methodology used for the assessment of ART centers in India yielded insights on the different domains that impact implementation and quality of service delivery. The design of this exercise may inform other researchers and managers planning similar large-scale assessments.

Microsatellite instability in stage II colorectal cancer: An Indian perspective.

INTRODUCTION: Around 80% of colorectal carcinoma are associated with chromosomal instability (CIN) while rest of 20 % are euploid, possessing defect in mis match repair system (MMR) quintessential for surveillance and correction of errors in introduced into microsatellites. MATERIALS AND METHODS: We analyse all stage II CRC for MSI who presented at MDTC at Army hospital (research and refrral) new delhi during last 2 years (Jan 14 to Dec 2015). RESULTS: We found that 22.2% patients out of 45 patients with stageII CRC being MSI-. high. We also noticed all suchcases were associated with loss of expression of PMS2 & MLH1, that was in contrast other studies where loss of MLH1 and MSH@, MSH6 were seen more commonly. CONCLUSION: MSI occurs in a significant proportion of colorectal cancers in young (<50 years old) patients. Young age at colorectal cancer diagnosis, proximal tumor location, family history of colorectal cancer were independent predictors of MSI status in our patients. In a proportion of these young patients with MSI tumors, loss of expression of proteins by 2 MMR genes PMS2 and hMLH1 has been identified.

Loss of heterozygosity of a locus on 17p13.3, independent of p53, is associated with higher grades of astrocytic tumours.

Amongst the human astrocytic tumours, the commonest of primary brain tumours, the clinical outcome of astrocytoma (AS) is significantly better than anaplastic astrocytoma (AA) and glioblastoma multiforme (GBM). Often, low grade tumours can progress to or recur with a more malignant phenotype. Recent loss of heterozygosity (LOH) reports suspect the involvement of a tumour suppressor gene, different from p53, in the 17p13.3 region of the human chromosome. However, the effect of LOH of 17p13.3 region on tumour histology at presentation and prognosis is as yet undefined. As a first step to define the role of this putative oncogene in astrocytic tumour progression, we correlated the LOH of a locus, D17S379, in 17p13.3 region and the p53 locus in 17p13.1 region with the histopathology of astrocytic tumours by PCR based microsatellite and restriction fragment length polymorphism of DNA extracted from microdissected paraffin sections of 45 astrocytic tumours of different histopathological grades. LOH of D17S379 was significantly associated (P=0.02) with AA and GBM (high grade malignancy), while no such preferential association was found with LOH of p53. There were no mutations in the exons 5 to 9 of p53 gene in the five tumours with LOH of D17S379 but not of p53 region. In a case of AA with a heterogenous microscopic appearance, heterozygosity of D17S379 was lost only in the area with a more malignant histology while both areas had no LOH or mutation of p53. A locus at the 17p13.3 region, independent of the p53 locus, is involved in a large subset of astrocytic tumours during transformation into a more malignant phenotype, and thus may be a link in the chain of genetic events occurring in astrocytic tumour progression.

Feasibility of implementing an integrated tool for improvement of treatment quality and early-warning indicators for HIV drug resistance: a pilot study of centres in India.

With the rapid scale-up in use of antiretroviral therapy (ART), monitoring the quality of care and factors that may lead to emergence of HIV drug resistance (HIVDR) is an important focus point for programme managers. The National AIDS Control Organisation of India embarked on strengthening the ART programme for continuous quality improvement (CQI), using defined quality-of-care indicators (QCIs), including World Health Organization (WHO) early-warning indicators (EWIs) for HIVDR. In this feasibility study, done during July 2014, an integrated QCI and EWI tool developed by WHO India was pilot tested across 18 purposively selected ART centres. At seven ART centres, the EWI 1 target of >90% on-time pill pick-up was achieved for adult patients, while among the paediatric age group (<15 years old) it was not achieved by any centre. EWI 2 (retention of patients in ART care at 12 months after initiation) showed that two centres had retention of both adult and paediatric patients of >85% at 12 months of ART, while 11 centres had retention between 75% and 85%. EWI 3 (pharmacy stock-out) for adult and paediatric patients showed that 11 ART centres reported a minimum of one stock-out for the first-line ART drugs in the reporting period, while EWI 4 targets (pharmacy dispensing practices) were achieved by all the centres, for both adults and children. Average retention in care at 6, 12 and 24 months after ART initiation was 82%, 77% and 71%, respectively. This feasibility study showed that EWI analyses were much simpler to conduct if information was sought only for patients receiving ART, for whom the quality of record-keeping is better and more consistent. The activity has highlighted the need for improved quality of record-keeping at the facilities and implementation of specific interventions to ensure better patient follow-up. After modifications, use of the tool will be phased in across all the ART centres in India.

The protective action of essential oils of onion and garlic in cholesterol-fed rabbits.

The effects of the essential oils of onion and garlic have been investigated in cholesterol-fed rabbits and have been compared with the effects of clofibrate. The marked rise in serum cholesterol and blood coagulability that followed 3 months of cholesterol feeding (0.2 g/kg/day) was significantly reduced by the essential oils of both onion and garlic. Fibrinolytic activity was actually increased even above the normal control levels. The essential oils of onion and garlic (equivalent to 1 g/kg/day of raw bulbs) proved more effective than clofibrate in the usual clinical dose of 33 mg/kg/day. Garlic was even more effective than onion. Cholesterol feeding increased the average lipid content of aorta from 5.95 to 13.75 mg/100 mg dry weight. With addition of clofibrate, onion or garlic the values were 7.79, 6.23 and 5.28 mg/100 ml, respectively. Thus it can be seen that the essential oils effectively prevent lipid acculation in the rabbit oarta.

Effect of essential oil of onion and garlic on experimental atherosclerosis in rabbits.

The effects of the essential oils of onion (extracted from 2 g of raw onion per kg body weight) and garlic (extracted from 1 g of raw garlic per kg body weight) have been observed on experimental atherosclerosis produced by cholesterol feeding (0.5 g/kg) in rabbits. The rise in serum cholesterol and serum triglycerides was significantly reduced by both onion and garlic during the 4-month period of study. Cholesterol feeding significantly increased beta-(P less than 0.01) and pre-beta (P less than 0.001) lipoproteins while decreasing the alpha-fraction (P less than 0.001). Onion and garlic both prevented these changes. The beta/alpha ratio, which was initially 1.6 : 1, rose to 4.5 : 1 and 5.7 : 1 at the end of 2 months and 4 months of cholesterol feeding. However, this ratio did not increase significantly, both at the 2-month and 4-month period, when onion and garlic were added. Fibrinolytic activity significantly increased with onion (P less than 0.001) and garlic (P less than 0.001) while feeding only cholesterol actually decreased it (P less than 0.001). Onion and garlic reducec aortic atheroma by about half. It is suggested that the essential oils of onion and garlic protect against experimental atherosclerosis by preventing the fall in the alpha lipoprotein fraction and by enhancing fibrinolytic activity, as well as by lowering the serum cholesterol and triglyceride levels.

Separation parameters via virtual migration distances in high-performance liquid chromatography, capillary zone electrophoresis and electrokinetic chromatography.

Among the various differential migration processes of separation, high-performance liquid chromatography (HPLC) and capillary zone electrophoresis (CZE) have emerged as the two major high-performance analytical techniques for separation of complex biological substances. In both HPLC and CZE with electroendoosmotic flow, the differential migration process can be divided into a separative component, which involves selective interactions with the stationary phase or differences in the electrophoretic migration velocities, and a non-separative component representing migration by convection that does not contribute directly to separation. The introduction of virtual migration distances leads to an additivity relationship for the two components that is applicable to both of the above techniques and facilitates the recognition of the underlying similarities as well as the expression and comparison of the various separation parameters. Examination of the key migration parameters led to the characterization and the classification of the various modes of CZE with electroendoosmotic flow. The treatment was extended to the analysis of capillary electrochromatography and micellar electrokinetic chromatography; two hybrid processes which exhibit features borrowed from HPLC and CZE. The use of virtual migration distances also led to a consistent and unified description of the characteristic parameters of these separation systems.

Displacement chromatography with on-column isomerization.

Displacement chromatography was simulated for the separation of two feed components interconverting by a reversible first order reaction and with Langmuirian adsorption behavior. The study was prompted by recent interest in the isolation of cis and trans forms of peptides containing one or more peptidyl-proline residues when the isomerization reaction interferes with the separation. The parameter values used in the simulations are similar to those found experimentally by reversed-phase chromatography and capillary electrophoresis of phenylalanine-proline dipeptide. From the concentration profiles computed by the finite difference scheme, the dependence of both the yield and production rate on the temperature, column length, flow velocity and displacer concentration was evaluated. The most important operational variable of the system is the temperature as it affects both the kinetic and adsorption parameters. The yield and production rate of the component of interest were evaluated as a function of the column length and displacer concentration under conditions that facilitate its efficient separation and the plots show an optimum. Nonetheless, optimal conditions for yield and production rate were considerably different. In the temperature range from 2 to 42 degrees C, the yield always decreases with increasing temperatures and for all the cases, optimum yield by displacement mandates the use of conditions such as pH, solvent and temperature under which the rate of interconversion is reduced to a level where it does not palpably interfere with the separation. On the other hand, under certain conditions optimal production rate can be obtained at higher temperatures.