In the present study, thin films of cadmium sulfide (CdS) of thickness ∼ 300 nm were used to bomb... more In the present study, thin films of cadmium sulfide (CdS) of thickness ∼ 300 nm were used to bombard with 350 keV argon (Ar4+) ions. The films were deposited on glass by thermal evaporation method. The irradiation was performed for ion fluences 1×1015, 3×1015 and 1×1016 ions/cm2 at normal incidence to study the modification in surface nanostructures as well as structural and optical properties of the films. The pristine and irradiated films were characterized by X-ray diffractometer, UV–visible spectroscopy and atomic force microscopy (AFM). The bombarded surface shows the evolution of structures from circular grains of wider size distribution to smaller grains (with a narrow distribution of sizes) with an increase in the ion fluence. X-ray diffraction of the pristine film shows the polycrystalline nature of the film with most intense peak at 26.49° along the (002) plane in a hexagonal phase. The crystallite size was found to be between 29 and 35 nm. The band gap of the pristine film was observed as 2.24 eV. The low-energy bombardment has resulted in the relaxation of strain and in an improvement in the crystallinity of the CdS films.
Objective: The cognitive and motivational attitudes to problem based learning (i.e., simple didac... more Objective: The cognitive and motivational attitudes to problem based learning (i.e., simple didactic problem stated in written form and Programmed Patient) has been compared with those to didactic lectures (DL), the traditional teaching method. The change in recall performance measured in MCQ tests was considered as a change in the cognitive domain. The first test was conducted one week after completion of the topic and second test was taken 3 months later, without prior information. The motivational change was recorded by open- ended questions about the learning method. Three groups of students at second MB BS professional year level consisting of 55, 57 and 59 people, were assigned a simple didactic problem stated in written form (SDP), programmed patients (PP), and didactic lecture (DL), respectively. Results: The average scores obtained by the learners in problem based learning (PBL) groups were similar to the students in the DL group in both the tests. Most of the students in PBL groups appreciated the exercise and suggested including more such exercises in the curriculum. These exercises helped them to better understand patient problems and prescribing behaviour as well as in development of communication skills. However, these exercises were time consuming and were not examination oriented. Conclusion: Pharmacotherapeutic teaching through PBL could be used within a traditional curriculum to develop relevant and rational use of drugs, provided the evaluation method was also modified.
This study establishes the widespread prevalence of fastidious or viable but non-culturable endop... more This study establishes the widespread prevalence of fastidious or viable but non-culturable endophytic bacteria in field shoots and in unsuspicious shoot-tip cultures of papaya (Carica papaya L.) against the norm of asepsis in vitro. A total of 150 shoot-tips (approximately 10 mm) were inoculated on MS-based culture medium after surface sterilization of field-derived axillary shoots of cv. Surya during November or January (100 and 50, respectively) when 35–50% cultures showed endophytic microbial growth on culture medium. Indexing of apparently clean cultures using bacteriological media helped in detecting and removing additional 14–17% stocks with covert bacteria during the first two passages. The rest of the stocks stayed consistently index-negative during the first eight subculture cycles, but appeared positive in PCR-screening undertaken thereafter employing universal bacterial 16S rRNA gene primers indicating the association of non-cultivable bacteria. Direct sequencing of the PCR product yielded overlapping nucleotide data signifying mixed template or the presence of diverse endophytic microorganisms. This was confirmed by light microscopy of tissue sap revealing viable bacteria in considerable numbers, which were detected under phase contrast or with negative staining. Planting tissue segments or applying homogenate from these stocks on diverse bacteriological media did not induce the organisms to grow in vitro. The shoot cultures displayed variation in growth and rooting potential, the onus of such variation was solely attributable to the associated microorganisms. The findings were confirmed with additional field shoots and fresh in vitro stocks established subsequently. The observations have implications in micropropagation and all other applications involving plant cell, tissue, organ, and protoplast culture.
In the present study, thin films of cadmium sulfide (CdS) of thickness ∼ 300 nm were used to bomb... more In the present study, thin films of cadmium sulfide (CdS) of thickness ∼ 300 nm were used to bombard with 350 keV argon (Ar4+) ions. The films were deposited on glass by thermal evaporation method. The irradiation was performed for ion fluences 1×1015, 3×1015 and 1×1016 ions/cm2 at normal incidence to study the modification in surface nanostructures as well as structural and optical properties of the films. The pristine and irradiated films were characterized by X-ray diffractometer, UV–visible spectroscopy and atomic force microscopy (AFM). The bombarded surface shows the evolution of structures from circular grains of wider size distribution to smaller grains (with a narrow distribution of sizes) with an increase in the ion fluence. X-ray diffraction of the pristine film shows the polycrystalline nature of the film with most intense peak at 26.49° along the (002) plane in a hexagonal phase. The crystallite size was found to be between 29 and 35 nm. The band gap of the pristine film was observed as 2.24 eV. The low-energy bombardment has resulted in the relaxation of strain and in an improvement in the crystallinity of the CdS films.
Objective: The cognitive and motivational attitudes to problem based learning (i.e., simple didac... more Objective: The cognitive and motivational attitudes to problem based learning (i.e., simple didactic problem stated in written form and Programmed Patient) has been compared with those to didactic lectures (DL), the traditional teaching method. The change in recall performance measured in MCQ tests was considered as a change in the cognitive domain. The first test was conducted one week after completion of the topic and second test was taken 3 months later, without prior information. The motivational change was recorded by open- ended questions about the learning method. Three groups of students at second MB BS professional year level consisting of 55, 57 and 59 people, were assigned a simple didactic problem stated in written form (SDP), programmed patients (PP), and didactic lecture (DL), respectively. Results: The average scores obtained by the learners in problem based learning (PBL) groups were similar to the students in the DL group in both the tests. Most of the students in PBL groups appreciated the exercise and suggested including more such exercises in the curriculum. These exercises helped them to better understand patient problems and prescribing behaviour as well as in development of communication skills. However, these exercises were time consuming and were not examination oriented. Conclusion: Pharmacotherapeutic teaching through PBL could be used within a traditional curriculum to develop relevant and rational use of drugs, provided the evaluation method was also modified.
This study establishes the widespread prevalence of fastidious or viable but non-culturable endop... more This study establishes the widespread prevalence of fastidious or viable but non-culturable endophytic bacteria in field shoots and in unsuspicious shoot-tip cultures of papaya (Carica papaya L.) against the norm of asepsis in vitro. A total of 150 shoot-tips (approximately 10 mm) were inoculated on MS-based culture medium after surface sterilization of field-derived axillary shoots of cv. Surya during November or January (100 and 50, respectively) when 35–50% cultures showed endophytic microbial growth on culture medium. Indexing of apparently clean cultures using bacteriological media helped in detecting and removing additional 14–17% stocks with covert bacteria during the first two passages. The rest of the stocks stayed consistently index-negative during the first eight subculture cycles, but appeared positive in PCR-screening undertaken thereafter employing universal bacterial 16S rRNA gene primers indicating the association of non-cultivable bacteria. Direct sequencing of the PCR product yielded overlapping nucleotide data signifying mixed template or the presence of diverse endophytic microorganisms. This was confirmed by light microscopy of tissue sap revealing viable bacteria in considerable numbers, which were detected under phase contrast or with negative staining. Planting tissue segments or applying homogenate from these stocks on diverse bacteriological media did not induce the organisms to grow in vitro. The shoot cultures displayed variation in growth and rooting potential, the onus of such variation was solely attributable to the associated microorganisms. The findings were confirmed with additional field shoots and fresh in vitro stocks established subsequently. The observations have implications in micropropagation and all other applications involving plant cell, tissue, organ, and protoplast culture.
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