... Purpura annularis telangiectoides with vasculitic ulcers treated with colchicine. Roma Pandhi... more ... Purpura annularis telangiectoides with vasculitic ulcers treated with colchicine. Roma Pandhi MD,; Rajesh Jain MD,; Bishan Das Radotra MD,; Bhushan Kumar MD. Article first published online: 16 JUL 2002. DOI: 10.1046/j.1365-4362.2002.01434.x. Issue. ...
Surgery for Obesity and Related Diseases, Volume 6, Issue 2, Pages 231, 4 March 2010, Authors:Vas... more Surgery for Obesity and Related Diseases, Volume 6, Issue 2, Pages 231, 4 March 2010, Authors:Vasha Kaur; Mohammad Mobasheri; Suleman Aktaa; Naresh Pore; Rajesh Jain; Cathy Edge; Marcus Reddy; Andrew Wan; David Hou. ...
Dexamethasone-cyclophosphamide pulse (DCP) is the prefered mode of therapy in pemphigus in India ... more Dexamethasone-cyclophosphamide pulse (DCP) is the prefered mode of therapy in pemphigus in India because it is relatively free from the side effects seen with heavy doses of daily oral steroids. One hundred forty-six pemphigus patients treated with DCP were observed for side effects of this regimen. One hundred forty mg of dexamethasone was administered IV in 200 ml of 5% dextrose over a period of 60-90 minutes on 3 consecutive days. Five hundred mg of cyclophosphamide was added on first day of the pulse and 50 mg given orally daily in the intervening period. DCP was repeated every 4 weeks and continued for 6 months after subsidence of the disease (no new lesions). Flushing over the face was the most common event recorded during the adiministration in 78 subjects followed by palpitations in 11, hiccups in 9, and numbness of feet in 6. Fourteen patients had polyurea, and 3 developed skin rash. Shivering, shooting pains along thighs, breathlessness, seizure and unilateral limb edema were observed in one patient each. Generalized weakness/malaise was the most troublesome delayed side effect in 81 (55.4%) patients; it lasted for 8-15 days after the pulse. Thirty-six (24.6%) had inadequate sleep syndrome, 23 (15.7%) had headache, 21 (14.3%) complained of arthralgias, 19 (13%) experienced alteration in taste, and 13 (9%) had diffuse hair loss. 28 females developed menstrual disturbances, and 14 (9.5%) had blurring of vision (glaucoma in 3 and posterior subcapsular cataract in 1). Thirteen of eighteen diabetics had an increase in blood sugar requiring higher doses of insulin. Five NIDDM patients needed insulin. Four (2.7%) developed hypertension. Pulse therapy is not absolutely free from side effects. Hypertension and diabetes occur less frequently as compared to conventional steroid therapy. Generalized weakness, flushing, headache and taste alteration occur exclusively with pulse therapy.
Indian Journal of Pathology and Microbiology, 2011
Conjunctivitis of the newborn is defined as hyperemia and eye discharge in the neonates and is a ... more Conjunctivitis of the newborn is defined as hyperemia and eye discharge in the neonates and is a common infection occurring in the neonates in the first month of life. In the United States, the incidence of neonatal conjunctivitis ranges from 1-2%, in India, the prevalence is 0.5-33% and varies in the world from 0.9-21% depending on the socioeconomic status. To study the organisms causing conjunctivitis of the newborn and to correlate the etiology with the mode of delivery. Single center, prospective, observational study. A total of 300 mothers and their newborns, born over a period of one year, were included in the study. Of these 200 newborns were delivered through vaginal route (Group A) and 100 (Group B) delivered by lower segment caesarean section (LSCS). At the time of labour, high vaginal swabs were taken from the mothers. Two conjunctival swabs each from both eyes of the newborn were collected at birth and transported to Microbiology department in a candle jar immediately. Eight babies in Group A, developed conjunctivitis at birth. None of the babies in Group B developed conjunctivitis, this difference was statistically highly significant (P<0.000). The organisms found in the conjunctiva of the newborns in Group A were Coagulase negative Staphylococcus, α hemolytic Streptococcus, Escherichia coli and Pseudomonas spps. However, the commonest organism leading to conjunctivitis in the newborn in this study was Coagulase negative Staphylococcus. It was observed that the mothers of 5 out of 8 babies (60%) developing conjunctivitis gave history of midwife interference and premature rupture of membranes so the presence of risk factors contribute to the occurrence of conjunctivitis in the newborn. It is inferred that the mode of delivery and the presence of risk factors is responsible for conjunctivitis in the newborn.
Journal of Physics and Chemistry of Solids - J PHYS CHEM SOLIDS, 2010
We present the first ever experimental Compton profiles of molybdenum dichalcogenides (MoX2; X=S ... more We present the first ever experimental Compton profiles of molybdenum dichalcogenides (MoX2; X=S and Te) using 20 Ci 137Cs Compton spectrometer. To interpret our experimental data, we have computed the theoretical profiles, energy bands and density of states using linear combination of atomic orbitals method in the framework of density functional theory and its hybridisation with Hartree Fock. The energy bands and density of states using full potential linearised augmented plane wave method have also been computed. Both theories show the existence of the indirect band gap. In addition, the relative nature of bonding is explained in terms of equal-valence-electron-density profiles and valence band charge densities.
The thermal behaviour of cellulose and its C-2, C-3 and C-6 derivatives substituted by acetyl, be... more The thermal behaviour of cellulose and its C-2, C-3 and C-6 derivatives substituted by acetyl, benzoyl and trityl groups has been studied in a static air medium by differential scanning calorimetry and thermogravimetry from ambient temperature to 450 ° C. Various reactions involved viz. dehydration, deacetylation, debenzoylation, detritylation, oxidative decomposition and oxidation of charred residues are discussed. Thermodynamic functions for different stages of thermal degradation are obtained from TG curves using the method of Broido. The activation energies for cellulose and its C-2, C-3 and C-6 substituted derivatives are found to be in the range 136 to 253 kJ mol−1. The IR spectra of these derivatives indicate formation of a compound containing CC and CO groups in the final residual char. The EPR signals indicate the formation of trapped and stable free radicals in the degradation of the compounds. Cellulose benzoate and its subsequent substituted derivatives show generation of a large amount of trapped free radicals during the decomposition. The mechanism of acid-catalysed thermal degradation of cellulose esters is proposed.
Studies on the flame-proofing and thermal stability imparted by the combination of chromium, mang... more Studies on the flame-proofing and thermal stability imparted by the combination of chromium, manganese, iron, cobalt, nickel, copper and zinc with cellulose ammonium phosphate were carried out by thermal, morphological and spectroscopic techniques. The samples were subjected to differential thermal analysis and thermogravimetric studies from ambient temperature to 900° C. Thermodynamic properties were obtained by using the Broido method on thermogravimetric curves. Infrared and reflectance UV-visible spectra of samples heated to significant temperatures were obtained. The samples showed low decomposition temperatures, low energies of activation and high char yields. Unmodified cellulose and other samples were pyrolysed in a temperature-programmed solid probe of a field ionization mass spectrometer, and mass spectra were recorded continuously throughout the pyrolysis to determine the relative amounts of volatile materials. In the treated cellulose samples the fractions of non-fuel volatiles increased and those of anhydroglucoses decreased. These observations confirm their flame-retardant effect. Scanning electron microscopic studies of the samples threw light on the morphological changes in the thermal degradation range. Based on the above studies, a mechanism of the thermal degradation of metal complexes of cellulose ammonium phosphate is proposed.
The kinetics of the thermal decomposition of cellulose and its esters (acetate, propionate, benzo... more The kinetics of the thermal decomposition of cellulose and its esters (acetate, propionate, benzoate, p-toluyate, α- and β-naphthoate and 9-anthroate), a phenoxy ester (phenoxyaceaceate). and chloro esters (chloroacetate, chloropropionate and chlorobenzoate) in air were studied by thermogravimetry and differential thermal analysis from ambient temperature to 650°C. From the resulting data, various thermodynamic parameters for different stages of thermal degradation of cellulose and its esters have been obtained following the methods of Freeman and Carroll, Broido, Dave and Chopra, and Chatterjee. The activation energies for the decomposition of cellulose and its esters were found to be in the range 85–240 kJ mol−1, but the free energies of activation are almost the same, viz., 165-180 kJ mol−1, indicating that the basic steps in the thermal degradation of cellulose and its esters are the same. A mechanism for the thermal degradation of cellulose esters is proposed. The IR spectra of the pyrolysis residues of cellulose esters indicate that dehydration takes place and a compound containing carbonyl groups is formed. X-Ray diffraction studies of cellulose and its esters showed that the acetylation of cellulose results in a more amorphous structure, which, on heat treatment up to 210°C, results in a sharp increase in the crystalline structure. This results in an increase in the decomposition temperature of the acetylated product of cellulose. Scanning electron microscopy studies of cellulose esters indicated that the fibrillar reaction sites have mostly reacted.
The enzyme biodegradability of xylan and of two of its prominent derivatives, (hydroxypropyl)xyla... more The enzyme biodegradability of xylan and of two of its prominent derivatives, (hydroxypropyl)xylan and xylan acetate, were examined comparatively vis-à-vis similar cellulose and starch derivatives, using a commercially available xylanase-rich enzyme preparation. The results indicate that xylan, like cellulose and its derivatives, is subject to enzymatic depolymerization in relation to degree of substitution. Degradation paralleled the presence of unmodified xylose units in the polysaccharide. Degradation proceeded rapidly, with greater than 80% of total degradation being complete after only 1 day. A comparison with starch and cellulose derivatives revealed that hydroxypropyl xylan suffers less biodegradability loss as substitution rises to 0.25 or 0.4, after which loss of degradability parallels that of the corresponding cellulose and starch derivatives. This apparent tolerance to low degrees of substitution is attributed to molecular heterogeneity which suggests that constituents other than xylose become propoxylated initially. Xylan acetate was found to lose enzymatic biodegradability at a rate which parallels that of cellulose acetate, and this is 35% slower (with respect to DS) than corresponding starch acetates. Size exclusion chromatography results suggest that xylan degrades to monosaccharides, that xylan derivatives degrade to monosaccharides and oligosaccharides, and that substitution with lignin prevents xylan from being recognized by xylanolytic enzymes, resulting in loss of degradability.
Cotton cellulose has been treated with tetrakis(hydroxymethyl)phosphonium chloride (THPC), urea a... more Cotton cellulose has been treated with tetrakis(hydroxymethyl)phosphonium chloride (THPC), urea and small amounts of ammonium dihydrogen orthophosphate (ADP) to impart flame retardancy. Complexes of cell-THPC-urea-ADP with transition metals such as chromium, manganese, iron, cobalt, nickel, copper and zinc have been characterized by reflectance UV-visible spectra. The samples were subjected to differential thermal analysis and thermogravimetry from ambient temperature to 700°C in air to study their thermal behaviour. From the resulting data, various kinetic parameters for different stages of thermal degradation were obtained following the method of Broido. For the decomposition of cellulose and flame-retardant celluloses, the activation energy was found to increase from 242 to 322kJ mol−1, the entropy of activation from 140 to 307 JK−1 mol−1 and the char yield from 2.5 to 31%. The free energy of activation for decomposition of cellulose and its derivatives was almost the same, viz. 148–162 kJ mol−1, indicating that the basic steps in the decomposition of cellulose and its derivatives are the same. The IR spectra of the thermally degraded residues of cell-THPC-urea-ADP and its metal complexes indicate that dehydration takes place and a compound containing the carbonyl group is formed. The electron paramagnetic resonance signals indicate the formation of trapped and stable free radicals in the thermal degradation of cellulose and its derivatives.
The isolation of non-cellulosic heteropolysaccharides (HetPS) from barley husks (Hordeum spp.) an... more The isolation of non-cellulosic heteropolysaccharides (HetPS) from barley husks (Hordeum spp.) and yellow poplar wood chips (Liriodendron tulipifera) was accomplished using mild steam explosion followed by extraction with water and ultrafiltration. The generally low yields, low purity, and low degree of polymerization (DP) improved when the HetPS were isolated following either alkali extraction of hammermilled or disk-refined biomass, or from holocellulose preparations generated by the conventional chlorite method or by organosolv delignification. Several purification methods were examined including precipitation using methanol; treatment with hydrogen peroxide (H2O2) or activated carbon (C) followed by precipitation with methanol; and H2O2-treatment followed by ultrafiltration. The isolation protocols were judged based on product yield, xylan content, and DP. The results indicate that, although steam explosion is effective in removing HetPS from the fiber source, virtually none remain in polymeric form. By contrast, alkali extraction succeeds in separating polymeric HetPS from the fiber source; and HetPS purity increases and polydispersity decreases with fiber prehydrolysis and delignification. Significant processing difficulties were attributed to the intimate association of HetPS with lignin which was effectively disrupted by acid-catalyzed pretreatment and treatment with H2O2. Ultrafiltration of H2O2-treated HetPS solutions represents the best procedure for isolating a xylan-rich polymer in high yield, with high DP and with high purity. Aqueous HetPS solutions can be spray- or freeze-dried into powderous products.
... Purpura annularis telangiectoides with vasculitic ulcers treated with colchicine. Roma Pandhi... more ... Purpura annularis telangiectoides with vasculitic ulcers treated with colchicine. Roma Pandhi MD,; Rajesh Jain MD,; Bishan Das Radotra MD,; Bhushan Kumar MD. Article first published online: 16 JUL 2002. DOI: 10.1046/j.1365-4362.2002.01434.x. Issue. ...
Surgery for Obesity and Related Diseases, Volume 6, Issue 2, Pages 231, 4 March 2010, Authors:Vas... more Surgery for Obesity and Related Diseases, Volume 6, Issue 2, Pages 231, 4 March 2010, Authors:Vasha Kaur; Mohammad Mobasheri; Suleman Aktaa; Naresh Pore; Rajesh Jain; Cathy Edge; Marcus Reddy; Andrew Wan; David Hou. ...
Dexamethasone-cyclophosphamide pulse (DCP) is the prefered mode of therapy in pemphigus in India ... more Dexamethasone-cyclophosphamide pulse (DCP) is the prefered mode of therapy in pemphigus in India because it is relatively free from the side effects seen with heavy doses of daily oral steroids. One hundred forty-six pemphigus patients treated with DCP were observed for side effects of this regimen. One hundred forty mg of dexamethasone was administered IV in 200 ml of 5% dextrose over a period of 60-90 minutes on 3 consecutive days. Five hundred mg of cyclophosphamide was added on first day of the pulse and 50 mg given orally daily in the intervening period. DCP was repeated every 4 weeks and continued for 6 months after subsidence of the disease (no new lesions). Flushing over the face was the most common event recorded during the adiministration in 78 subjects followed by palpitations in 11, hiccups in 9, and numbness of feet in 6. Fourteen patients had polyurea, and 3 developed skin rash. Shivering, shooting pains along thighs, breathlessness, seizure and unilateral limb edema were observed in one patient each. Generalized weakness/malaise was the most troublesome delayed side effect in 81 (55.4%) patients; it lasted for 8-15 days after the pulse. Thirty-six (24.6%) had inadequate sleep syndrome, 23 (15.7%) had headache, 21 (14.3%) complained of arthralgias, 19 (13%) experienced alteration in taste, and 13 (9%) had diffuse hair loss. 28 females developed menstrual disturbances, and 14 (9.5%) had blurring of vision (glaucoma in 3 and posterior subcapsular cataract in 1). Thirteen of eighteen diabetics had an increase in blood sugar requiring higher doses of insulin. Five NIDDM patients needed insulin. Four (2.7%) developed hypertension. Pulse therapy is not absolutely free from side effects. Hypertension and diabetes occur less frequently as compared to conventional steroid therapy. Generalized weakness, flushing, headache and taste alteration occur exclusively with pulse therapy.
Indian Journal of Pathology and Microbiology, 2011
Conjunctivitis of the newborn is defined as hyperemia and eye discharge in the neonates and is a ... more Conjunctivitis of the newborn is defined as hyperemia and eye discharge in the neonates and is a common infection occurring in the neonates in the first month of life. In the United States, the incidence of neonatal conjunctivitis ranges from 1-2%, in India, the prevalence is 0.5-33% and varies in the world from 0.9-21% depending on the socioeconomic status. To study the organisms causing conjunctivitis of the newborn and to correlate the etiology with the mode of delivery. Single center, prospective, observational study. A total of 300 mothers and their newborns, born over a period of one year, were included in the study. Of these 200 newborns were delivered through vaginal route (Group A) and 100 (Group B) delivered by lower segment caesarean section (LSCS). At the time of labour, high vaginal swabs were taken from the mothers. Two conjunctival swabs each from both eyes of the newborn were collected at birth and transported to Microbiology department in a candle jar immediately. Eight babies in Group A, developed conjunctivitis at birth. None of the babies in Group B developed conjunctivitis, this difference was statistically highly significant (P<0.000). The organisms found in the conjunctiva of the newborns in Group A were Coagulase negative Staphylococcus, α hemolytic Streptococcus, Escherichia coli and Pseudomonas spps. However, the commonest organism leading to conjunctivitis in the newborn in this study was Coagulase negative Staphylococcus. It was observed that the mothers of 5 out of 8 babies (60%) developing conjunctivitis gave history of midwife interference and premature rupture of membranes so the presence of risk factors contribute to the occurrence of conjunctivitis in the newborn. It is inferred that the mode of delivery and the presence of risk factors is responsible for conjunctivitis in the newborn.
Journal of Physics and Chemistry of Solids - J PHYS CHEM SOLIDS, 2010
We present the first ever experimental Compton profiles of molybdenum dichalcogenides (MoX2; X=S ... more We present the first ever experimental Compton profiles of molybdenum dichalcogenides (MoX2; X=S and Te) using 20 Ci 137Cs Compton spectrometer. To interpret our experimental data, we have computed the theoretical profiles, energy bands and density of states using linear combination of atomic orbitals method in the framework of density functional theory and its hybridisation with Hartree Fock. The energy bands and density of states using full potential linearised augmented plane wave method have also been computed. Both theories show the existence of the indirect band gap. In addition, the relative nature of bonding is explained in terms of equal-valence-electron-density profiles and valence band charge densities.
The thermal behaviour of cellulose and its C-2, C-3 and C-6 derivatives substituted by acetyl, be... more The thermal behaviour of cellulose and its C-2, C-3 and C-6 derivatives substituted by acetyl, benzoyl and trityl groups has been studied in a static air medium by differential scanning calorimetry and thermogravimetry from ambient temperature to 450 ° C. Various reactions involved viz. dehydration, deacetylation, debenzoylation, detritylation, oxidative decomposition and oxidation of charred residues are discussed. Thermodynamic functions for different stages of thermal degradation are obtained from TG curves using the method of Broido. The activation energies for cellulose and its C-2, C-3 and C-6 substituted derivatives are found to be in the range 136 to 253 kJ mol−1. The IR spectra of these derivatives indicate formation of a compound containing CC and CO groups in the final residual char. The EPR signals indicate the formation of trapped and stable free radicals in the degradation of the compounds. Cellulose benzoate and its subsequent substituted derivatives show generation of a large amount of trapped free radicals during the decomposition. The mechanism of acid-catalysed thermal degradation of cellulose esters is proposed.
Studies on the flame-proofing and thermal stability imparted by the combination of chromium, mang... more Studies on the flame-proofing and thermal stability imparted by the combination of chromium, manganese, iron, cobalt, nickel, copper and zinc with cellulose ammonium phosphate were carried out by thermal, morphological and spectroscopic techniques. The samples were subjected to differential thermal analysis and thermogravimetric studies from ambient temperature to 900° C. Thermodynamic properties were obtained by using the Broido method on thermogravimetric curves. Infrared and reflectance UV-visible spectra of samples heated to significant temperatures were obtained. The samples showed low decomposition temperatures, low energies of activation and high char yields. Unmodified cellulose and other samples were pyrolysed in a temperature-programmed solid probe of a field ionization mass spectrometer, and mass spectra were recorded continuously throughout the pyrolysis to determine the relative amounts of volatile materials. In the treated cellulose samples the fractions of non-fuel volatiles increased and those of anhydroglucoses decreased. These observations confirm their flame-retardant effect. Scanning electron microscopic studies of the samples threw light on the morphological changes in the thermal degradation range. Based on the above studies, a mechanism of the thermal degradation of metal complexes of cellulose ammonium phosphate is proposed.
The kinetics of the thermal decomposition of cellulose and its esters (acetate, propionate, benzo... more The kinetics of the thermal decomposition of cellulose and its esters (acetate, propionate, benzoate, p-toluyate, α- and β-naphthoate and 9-anthroate), a phenoxy ester (phenoxyaceaceate). and chloro esters (chloroacetate, chloropropionate and chlorobenzoate) in air were studied by thermogravimetry and differential thermal analysis from ambient temperature to 650°C. From the resulting data, various thermodynamic parameters for different stages of thermal degradation of cellulose and its esters have been obtained following the methods of Freeman and Carroll, Broido, Dave and Chopra, and Chatterjee. The activation energies for the decomposition of cellulose and its esters were found to be in the range 85–240 kJ mol−1, but the free energies of activation are almost the same, viz., 165-180 kJ mol−1, indicating that the basic steps in the thermal degradation of cellulose and its esters are the same. A mechanism for the thermal degradation of cellulose esters is proposed. The IR spectra of the pyrolysis residues of cellulose esters indicate that dehydration takes place and a compound containing carbonyl groups is formed. X-Ray diffraction studies of cellulose and its esters showed that the acetylation of cellulose results in a more amorphous structure, which, on heat treatment up to 210°C, results in a sharp increase in the crystalline structure. This results in an increase in the decomposition temperature of the acetylated product of cellulose. Scanning electron microscopy studies of cellulose esters indicated that the fibrillar reaction sites have mostly reacted.
The enzyme biodegradability of xylan and of two of its prominent derivatives, (hydroxypropyl)xyla... more The enzyme biodegradability of xylan and of two of its prominent derivatives, (hydroxypropyl)xylan and xylan acetate, were examined comparatively vis-à-vis similar cellulose and starch derivatives, using a commercially available xylanase-rich enzyme preparation. The results indicate that xylan, like cellulose and its derivatives, is subject to enzymatic depolymerization in relation to degree of substitution. Degradation paralleled the presence of unmodified xylose units in the polysaccharide. Degradation proceeded rapidly, with greater than 80% of total degradation being complete after only 1 day. A comparison with starch and cellulose derivatives revealed that hydroxypropyl xylan suffers less biodegradability loss as substitution rises to 0.25 or 0.4, after which loss of degradability parallels that of the corresponding cellulose and starch derivatives. This apparent tolerance to low degrees of substitution is attributed to molecular heterogeneity which suggests that constituents other than xylose become propoxylated initially. Xylan acetate was found to lose enzymatic biodegradability at a rate which parallels that of cellulose acetate, and this is 35% slower (with respect to DS) than corresponding starch acetates. Size exclusion chromatography results suggest that xylan degrades to monosaccharides, that xylan derivatives degrade to monosaccharides and oligosaccharides, and that substitution with lignin prevents xylan from being recognized by xylanolytic enzymes, resulting in loss of degradability.
Cotton cellulose has been treated with tetrakis(hydroxymethyl)phosphonium chloride (THPC), urea a... more Cotton cellulose has been treated with tetrakis(hydroxymethyl)phosphonium chloride (THPC), urea and small amounts of ammonium dihydrogen orthophosphate (ADP) to impart flame retardancy. Complexes of cell-THPC-urea-ADP with transition metals such as chromium, manganese, iron, cobalt, nickel, copper and zinc have been characterized by reflectance UV-visible spectra. The samples were subjected to differential thermal analysis and thermogravimetry from ambient temperature to 700°C in air to study their thermal behaviour. From the resulting data, various kinetic parameters for different stages of thermal degradation were obtained following the method of Broido. For the decomposition of cellulose and flame-retardant celluloses, the activation energy was found to increase from 242 to 322kJ mol−1, the entropy of activation from 140 to 307 JK−1 mol−1 and the char yield from 2.5 to 31%. The free energy of activation for decomposition of cellulose and its derivatives was almost the same, viz. 148–162 kJ mol−1, indicating that the basic steps in the decomposition of cellulose and its derivatives are the same. The IR spectra of the thermally degraded residues of cell-THPC-urea-ADP and its metal complexes indicate that dehydration takes place and a compound containing the carbonyl group is formed. The electron paramagnetic resonance signals indicate the formation of trapped and stable free radicals in the thermal degradation of cellulose and its derivatives.
The isolation of non-cellulosic heteropolysaccharides (HetPS) from barley husks (Hordeum spp.) an... more The isolation of non-cellulosic heteropolysaccharides (HetPS) from barley husks (Hordeum spp.) and yellow poplar wood chips (Liriodendron tulipifera) was accomplished using mild steam explosion followed by extraction with water and ultrafiltration. The generally low yields, low purity, and low degree of polymerization (DP) improved when the HetPS were isolated following either alkali extraction of hammermilled or disk-refined biomass, or from holocellulose preparations generated by the conventional chlorite method or by organosolv delignification. Several purification methods were examined including precipitation using methanol; treatment with hydrogen peroxide (H2O2) or activated carbon (C) followed by precipitation with methanol; and H2O2-treatment followed by ultrafiltration. The isolation protocols were judged based on product yield, xylan content, and DP. The results indicate that, although steam explosion is effective in removing HetPS from the fiber source, virtually none remain in polymeric form. By contrast, alkali extraction succeeds in separating polymeric HetPS from the fiber source; and HetPS purity increases and polydispersity decreases with fiber prehydrolysis and delignification. Significant processing difficulties were attributed to the intimate association of HetPS with lignin which was effectively disrupted by acid-catalyzed pretreatment and treatment with H2O2. Ultrafiltration of H2O2-treated HetPS solutions represents the best procedure for isolating a xylan-rich polymer in high yield, with high DP and with high purity. Aqueous HetPS solutions can be spray- or freeze-dried into powderous products.
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