Application of Peleg's equation to describe creep responses of potatoes under constant and variable storage conditions.

The application of Peleg's equation to characterize creep behavior of potatoes during storage was investigated. Potatoes were stored at 25, 15, 5C, and variable (fluctuating) temperature for 16 or 26 weeks. The Peleg equation adequately described the creep response of potatoes during storage at all storage conditions (R2 = .97to .99). Peleg constant k1 exhibited a significant (p < .05) decreasing trend with storage time (ts ) for samples stored under the experimental conditions whereas the constant k2 appeared to be unaffected much by ts except for samples stored at 25C. Under constant temperature storage, k1 was found to be a linear function of ts (R2 = .87 to .97). Also, the rate of change of k1 appeared to be temperature dependent described by a linear relationship between the degradation rate constant for k1 (α) and storage temperature (T). For the variable storage condition, a bulk mean temperature (Tbm ) was calculated to account for a series combination of storage time and temperature which the potatoes were subjected to. It was possible to describe the changes in k1 due to variable storage temperature in terms of Tbm and ts using stepwise multiple regression (R2 = . 94). PRACTICAL APPLICATIONS: Precise description of the changes in the rheological properties of raw potatoes during storage could help predict the associated effect on the texture of cooked potatoes. Easy and simple methods of describing creep responses during storage or processing will be potentially helpful to better understand the phenomenon. The model parameters from such model could be used to relate rheological properties of raw and cooked potatoes. Moreover, the model parameters could be used to establish relationship between instrumental and sensory attributes which will help in the prediction of sensory attributes from instrumental data.

The role of N dopant in inducing ferromagnetism in (ZnO)n clusters (n = 1-16).

The effect of nitrogen doping on the magnetic properties of (ZnO)(n) clusters (n = 1-16) has been investigated using spin polarized density functional theory. The total energy calculations suggest that N is more stable at the O site than at the Zn site in (ZnO)(n) clusters and induces a magnetic moment of 1 µ(B)/N atom. The N-Zn-N configuration is more stable than isolated N for 3D structures. The N dopants do not show any tendency for clustering. The binding energy is found to decrease with the increase in the number of N dopants. The magnetic moment increases gradually with the increase in the number of atoms with 1 µ(B)/N atom for n ≤ 4 and less than 1 µ(B)/N for n > 4. The local magnetic moment is mainly localized at the N site with a small magnetic moment induced at the O site. The presence of a Zn vacancy (V(Zn)) induced an additional magnetic moment of 2 µ(B) on the nearest O atoms. The N dopant prefers to form a N-V(Zn) pair. The combination of N and V(Zn) in 3D structures leads to a total magnetic moment of 3 µB. The Mulliken charge transfers from Zn to N and O in all N doped (ZnO)(n) clusters. The calculated results are consistent with existing experimental and theoretical results.

Transition metal induced magnetism in smaller fullerenes (Cn for n≤36).

The magnetic properties of 3d transition metals (TM) encapsulated inside smaller fullerenes ranging from C20 to C36 have been investigated using spin polarized density functional theory. The TM impurities stabilize asymmetrically at an off-center position for n≥28. The total magnetic moment (MM) of TM@Cn complexes are largely contributed by TMs and a small amount of MM of 0.12-0.50 µB is induced on the cage carbon atoms. The 3d TM atoms interact with C atoms of C20 and C28 cage ferromagnetically (FM) except for Ni@C28 which shows antiferromagnetic (AFM) interaction. The magnetic interactions change from FM to AFM in C32 cage for Ti, V, Cr and Mn. The MM gets quenched in Ni@Cn for n≥32. The total MM of Mn@Cn does not show any change although the nature of magnetic interactions changes from FM to AFM at n=32. Ti and V are the only TMs which show positive cohesive energy in all fullerenes considered. The smallest fullerene which can encapsulate all 3d TM are Cn for n≥32, consistent with available experimental and theoretical results.

Structural, electronic, and vibrational properties of C(60-n)Nn (n = 1-12).

Ab initio investigation of structural, electronic and vibrational properties of nitrogen-doped fullerenes (C(60-n)Nn, for n = 1-12) has been performed using numerical atomic orbital density functional theory. We have obtained the ground-state structures for C(60-n)Nn for n = 1-12, which show higher stability with a single nitrogen in a pentagon and two nonadjacent nitrogen atoms in a hexagon. Nitrogen doping leads to structural deformation, with the diameter showing variation from (7.14 - 0.24) to (7.14 + 0.10) A. The average diameter of C(60-n)Nn shows a small decrease for n > or = 5, with a minimum value of 7.06 A for n = 12. The change in the average diameter signifies the volume contraction, which is also maximum for C48N12. The binding energy per atom is found to decrease as a function of the number of N atoms. The HOMO-LUMO gap is found to decrease with an increase in substitutional nitrogen atoms; however, no systematic pattern could be observed. The Mulliken charge analysis performed on all optimized geometries shows a charge transfer of -0.3 to -0.45 (or 0.3-0.45 electrons) from nitrogen to carbon atoms, resulting in nitrogen atoms behaving as electrophilic sites. The harmonic vibrational frequency analysis shows the absence of any imaginary mode. The vibrational frequencies are found to decrease with an increase in the number of nitrogen atoms in C(60-n)Nn. The results obtained are consistent with available theoretical and experimental results.

Simple tests for rapid assessment of the quality of raw milk.

Simple and inexpensive tests are described for rapid qualitative assessment of the microbiological quality of raw milk. These tests included the monitoring of dissolved oxygen levels and changes in the color of raw milk with time in a slightly modified methylene blue test using 16 ppm of dye concentration. The initial bacterial population in raw milk determined by standard plate count could be estimated with coefficients of determination (r2) of about 0.697 and 0.613 from the respective normalized voltage outputs of the dissolved oxygen probe and light-sensing probes at selected time intervals in less than 1 h. However, a comparison of experimental and estimated initial bacterial populations in raw milk showed correlation coefficients (r) of about 0.754 and 0.616 for the dissolved oxygen probe and light-sensing probe, respectively. These results clearly indicated the potential and need for improving such empirical models for grading raw milk with both types of probes.

Impedance of goat eye lens at different DC voltages.

A computer assisted AC impedance system is used to measure the DC voltage-current (V-I) characteristics and AC impedance of a goat eye lens using a two-probe Ag-AgCl electrode system. The measurement of the V-I characteristics shows that when a DC voltage from 0 mV to 30 mV is applied, the resultant current decreases from an initial value of 0.58 microA to 0.006 microA. However, when the voltage is increases beyond 30 mV, the current increases and reaches a value of 0.9 microA at 100 mV. The data on the frequency response (0.01-10 Hz) of the impedance of lens tissue show an inverse relationship with frequency. The effect of various DC voltages, namely 0, 30, 50, 100 and 200 mV, on the impedance of the eye lens is also investigated over a frequency range of 0.01-10 Hz. The measurement results for both V-I characteristics and AC impedance further suggest the presence of a 30 mV voltage compartment in the goat eye lens.

Impedance of a goat eye lens.

The complex electrical impedance of a goat eye lens is studied in the frequency range 10 mHz-10 Hz at room temperature, using a computer-controlled AC impedance system. AC impedance software (model 368, version 2.2) is employed to determine the total impedance and capacitance of the eye lens at various frequencies. A Cole-Cole plot of the eye lens material is drawn between the real component of impedance Z' and the imaginary component Z" for each excitation frequency that shows a perfect arc of a-semicircle, with its centre lying below the abscissa at an angle of 35 degrees. The half-angle phi between R(0) and R infinity is found to be 55 degrees, which mathematically demonstrates the selective permeability of the eye lens. Using graphical analysis of the Cole-Cole plot, characteristic frequency fc and distribution factor alpha are observed to be 1 Hz and 0.77, respectively. At characteristic frequency, capacitance and total impedance are found to be 1.14 microF and 9.08 k omega. The effect of electrode polarisation on capacitance is corrected, based on Fricke's power function. The observed electrical parameters are then used to explain the multiple current path through various tissue compartments. Further, an attempt is made to explain the results on the basis of a possible dipolar model.

Phenotypic analysis of resident lymphoid cells in the conjunctiva and adnexal tissues of rat.

The conjunctival associated lymphoid tissue is considered to be an integral part of the mucosal immune system. Under normal circumstances immune mechanisms in mucosal associated lymphoid tissue of the gut and bronchus can selectively suppress, rather than enhance, immune responsiveness to encountered antigens, inducing a state of tolerance. It is possible that conjunctival associated lymphoid tissue can also induce a state of tolerance to encountered antigens. Such a response may be exploited to modulate immune mediated ocular disease. Enhanced tolerance may protect the host against foreign antigen. Alternatively, under certain circumstances when the normal immune system is altered or disrupted the mucosal tissue may act to induce sensitisation and trigger immune mediated disease. The rat is frequently used as an animal model of immune mediated eye disease, but the normal profile of immune cells in the rat conjunctiva has not been studied. This information is essential for meaningful interpretation in the experimental situation. In this study we examined the immunophenotype of lymphoid tissue associated with the conjunctiva, lacrimal gland and Harderian gland of the Lewis rat. CD4+, Ia+ and the monocyte/macrophage population of cells were found predominantly in the substantia propria of the conjuctiva and interstitial connective tissue of the glands. CD8+ cells were distributed mainly in relation to the conjunctival and glandular epithelium. Goblet cells stained strongly with the monoclonal antibody (MAb) MRC OX-39, which is a marker for IL-2 receptors. The overall pattern of distribution of immunocompetent cells in the rat was found to be similar to that reported in humans.

The effect of topical cyclosporin on conjunctiva-associated lymphoid tissue (CALT).

Topical cyclosporin A is increasingly being used in the treatment of ocular surface immune-mediated disorders. The availability of the drug in oil-based vehicles or collagen shields has restricted its use because of ocular irritation or blurring of vision. Although topical cyclosporin is being used more frequently, its effect on the immunocompetent cells of the conjunctiva is not known. Our aim was to study the effect of cyclosporin instillation on the immunocomponent cells of conjunctiva-associated lymphoid tissue (CALT) of Lewis rat, using a novel method of topical drug delivery. A suspension of collagen bits impregnated with cyclosporin A was instilled into eyes of Lewis rats for 4 days (group 1) or 8 days (group 2). Control rats (group 3) received the suspension without cyclosporin. Frozen sections of eyelids and conjunctiva were immunostained with the following monoclonal antibody markers: W3/13 (CD3), W3/25 (CD4, macrophages), OX-8 (CD8), MARD-3 (B cells), ED1, ED2 (macro/monocytes), OX-6 (class II MHC, Ia) and OX-39 (CD25, IL-2 receptor). Intraepithelial (IE) and substantia propria cells for each subset were counted and expressed as numbers per section. By day 8, intraepithelial and substantia propria cells for all the above markers, except B cells, showed a significant reduction in numbers. The p values were < 0.02 for W3/13 (CD3), W3/25 (CD4), OX-8 (CD8), OX-39 (CD25) (IE only), ED1, ED2 and OX-6 positive cells. Goblet cells of control animals showed strong positive reaction with OX-39 (CD25) antibody. This was completely abolished following 8 days of topical cyclosporin. This study demonstrated that topical cyclosporin A induces a marked reduction in numbers of all subtypes of immunocompetent cells in the conjunctival epithelium and substantia propria.

Mucosa specific lymphocytes in the human conjunctiva, corneoscleral limbus and lacrimal gland.

Conjunctiva associated lymphoid tissue shows several similarities to mucosa associated lymphoid tissue of the gut and respiratory tract. These similarities have been described in relation to lymphocyte subpopulations and epithelial cell morphology. However, unlike the lymphoid tissue of the gut and respiratory tract, mucosa specific lymphocytes have not been described in the ocular mucosa. In this study we demonstrated the presence of mucosa specific lymphocytes bearing the Human Mucosal Lymphocyte-1 antigen (beta 7 integrin), in the human conjunctiva, limbus and lacrimal gland. The distribution of this subset of lymphocytes corresponded to the distribution of CD8+ T-cells and was found maximally in the epithelium of the epibulbar conjunctiva and in the lacrimal gland. The Human mucosal lymphocyte antigen may function to determine mucosal homing of this particular subset of CD8+ T-cells, which in turn, may have special function in immunological defense and tolerance mechanisms occurring at mucosal surfaces.