Period T1 Research Articles

Feeding habits of three round stingrays (Rajiformes: Urotrygonidae) in the central Mexican Pacific

Stomach contents and dietary overlap of three round stingray species (Urobatis halleri, Urotrygon munda, and Urotrygon rogersi) captured off the central Pacific coast of Mexico were analyzed during the two main hydroclimatic periods (T1 and T2) that characterize the environmental variability in the area. The three round stingray species showed a narrow bathymetric distribution range, and the highest abundances were located at 20 m depth in both seasons. In general, the diets were mainly composed of benthic microcrustaceans (caridean shrimps) and to a lesser extent of fishes, polychaetes, and molluscs. The most abundant prey items in the diets were carideans of the families Processidae and Ogyriididae, and penaeids, followed by brachyuran and stomatopod larvae. All three stingrays exhibited a generalist feeding strategy. The diets showed high overlap values during period T1 in both inter- and intraspecies analyses, but lower values during period T2. There was no evidence of ontogenetic diet changes and sex was not a factor for trophic differences. The slight differences among diets were due to seasonal changes in the soft-bottom macrobenthic invertebrate assemblages in the shallow waters, and relationships like predation and competition were not the main factors influencing the population dynamics of the three stingray species.

A new optical method of continuously analysing the surface properties of a single pendant drop while obtaining quality bulk spectral and refractive index measurements of the liquid-under-test

The classical stalagmometer has been replaced by the tensiometer to measure surface properties from drop volume. From the drop period T1, converted into volume, the surface properties of the liquid can be obtained. In the fibre drop analyser the use of the graphical signal (tensiotrace), significantly extends the measurement potential of the tensiometer by providing additional measurands. This instrument produces a series of peaks. The third-order reflection is known as 'the tensiopeak-period' t3, and accurately predicts the value of the drop period. The results of an experimental study confirm the relationship between T1 and t3 for a wide range of liquids and are supported by ray-tracing modeling. Very sensitive and high quality bulk UV-visible spectra and refractive index measurements can be obtained from the drop-under-test.

Cricket: Nature and incidence of fast-bowling injuries at an elite, junior level and associated risk factors

Objective. To compile an injury profile of 46 fast bowlers aged 11 - 18 years, and to identify the associated risk factors for injury during one academy cricket season. Methods. The fast bowlers selected were tested and observed for one academy cricket season (March - November). Subjects were grouped into injury classifications (uninjured=S1; injured but able to play=S2; injured and unable to play=S3). Anthropometrical and postural data for the subjects were collected preseason (T1). Physical fitness screenings were conducted and the relationship between fitness and occurrence of injuries was assessed. Additional factors such as bowling techniques and bowling workload were assessed. A regression analysis was conducted to analyse the relationship between bowling workload and weeks incapacitated. Results. Fifteen per cent of the subjects remained injury free for the duration of the season. The incidence of serious injury (S3) showed a statistical and moderate, practical significant increase (V=0.23, df≥2) throughout the data collection period (4% at T1 - 30% at T3 (post-season)). The most common injuries were to the knee (41%) and lower back (37%), occurring from mid-season (T2) to T3. The nature of the injuries was predominantly strains (39%) and ‘other' (39%), with the highest reported incidence during the period T1 - T3. Sprains followed, with an overall incidence of 14%. Subjects were incapacitated approximately 1 out of every 7 weeks of play. The S1 and S2 bowlers performed consistently better than the S3 bowlers in all the fitness variables tested. Bowling workload presented a statistically significant (p

44: A Pilot Study of Electronic Diary Self Reports of Affect in Adolsecents with Anorexia

Anorexia nervosa (AN) causes significant morbidity in adolescents, but the influences of affect on behaviors are poorly understood. Collection of real time data from patients using Ecologic Momentary Assessment (EMA) allows temporal association of state affect with behavioral events. This pilot study uses a novel cell phone tool to establish feasibility of EMA in adolescents with AN and to evaluate inter- and intra-day variations in affect. Subjects (n = 8) were AN patients (ages 13–26) of an outpatient eating disorders center. Subjects used the personal digital assistant portion of the Treo 650 cell phone to complete daily and random-signal electronic diary questionnaires daily for up to 28 days. Immediately after completion, subjects synchronized data directly into the research database using the wireless phone network. State affect was measured 6 times daily (T1 [8 – 10:19 am]; T2 [10:20 – 12:39 pm]; etc., until 9:59 pm) using 3-positive (Happy, Energetic, Excited) and 3-negative (Sad, Angry, Upset) items from the Positive and Negative Affect Scale (PANAS). Average daily affect was measured with the full 20-item PANAS. An exit questionnaire and interview assessed reactions to the experience. Preliminary analysis of the first 4 subjects revealed 2 completed 28 days of data collection and 2 completed 24 days. One subject was withdrawn due to an admission scheduled after study entry and one was confused about start/stop dates. Subjects reported that the cell phones were easy to use (mean = 4.2; 1 = very hard to 5 = very easy). Daily electronic diary compliance rates were high (92%). Within the random-signal diaries, compliance ranged from 83-100% for the first 3 weeks, but dropped to 79% for days 23-28 (total rate 88%). Within days, the first time interval (T1) had a compliance rate of only 78%, mostly due to one subject who completed only 46% of the T1 diaries. The remaining subjects completed 88%, similar to the rates in the remaining intervals. Average daily (full PANAS) affect scores across subjects and days was 10.57 (SD 6.11) for positive and 7.53 (SD 5.51) for negative. Within days, random-signal (6-item PANAS) positive affect was lowest in period T6 (2.59, SD 2.18) and highest in period T5 (3.83, SD 2.39). Negative affect was lowest in period T1 (1.72, SD 1.87) and highest in period T3 (2.05, SD 2.16). These data show feasibility of this method to capture expected variations in affect in adolescents with AN. We found greater variation in positive affect at relatively higher levels than negative affect. Overall, negative affect was somewhat flat. Demonstration of mood variation may be useful in understanding eating and exercise behaviors characteristic of AN.

Identification of Lifted Models for General Dual-Rate Sampled-Data Systems Using N4SID Algorithm

The technological and the economical reasons often make the researchers and engineers encounter the so-called multirate sampled-data systems which include multiple sampleddata mechanisms with different sampling periods. As a class of multi-rate systems, general dual-rate systems are very attractive because the contributions in the literature of the dual-rate systems can be easily extended to the whole scope of multi-rate sampled system. In this research, we consider the identification problems for the general dual-rate systems. A general dual-rate system is illustrate Fig. 1. In Fig. 1, u(kT1) and y(kT2) are the dual-rate system input and output signals and the sampling period T1 = T2. y(kT2) is corrupted by a stochastic noise v(kT2). The measurement of the output is denoted by z(kT2) . ZOH is a zero order holder with period T1. ADC is a sampler with period T2. Pc is a linear time-invariant(LTI) continuous-time process. Suppose that the samplers and zero order holders are synchronized at time t = 0. Most typical identification algorithms only handle the identification problems of single-rate systems. However, a single-rate LTI isomorphism can be obtained for the dualrate system in Fig.1 by the lifting technique. The isomorhpism is the so-called lifted model, Although there are several contributions in the literature for the identification problems of the lifted models, most of them need detailed prior information about the dual-rate system, e.g. observability structure indexes which cannot be obtained in many cases. In contrast, Subspace State-Space IDentification(4SID) algorithms need no prior information about the systems under investigation. Unfortunately, it is commented that the 4SID type algorithm cannot be used to the lifted models because of the causality constraints.

The Effect of Daily Consumption of Probiotic and Conventional Yoghurt on Oxidant and Antioxidant Parameters in Plasma of Young Healthy Women

In recent years there has been increasing interest in the potential beneficial effects of probiotic bacteria, particularly concerning their immune-modulating effects. Considering the involvement of free radicals in immunological processes, we tried to verify and compare the effects of probiotic (Lactobacillus casei) and conventional yoghurt on antioxidant and oxidant parameters in plasma of humans. In this study female volunteers consumed 100 g/day of probiotic (n = 17) or conventional yoghurt (n = 16) for two weeks (T1-T2) and 200 g/day for another two weeks (T2-T3). A wash-out phase lasting two weeks followed. Total antioxidant capacity (TAC), albumin, and bilirubin were determined photometrically, uric acid was determined by enzymatic methods, and vitamin E, carotenoids, malondialdehyde (MDA), and conjugated dienes (CD) were measured using high-performance liquid chromatography (HPLC). In the period of continuous yoghurt intake (T1-T3), mean concentrations of the antioxidants vitamin E, lycopene, and zeaxanthin decreased significantly (p < 0.01) in the probiotic and in the control group. The average concentrations of lutein, beta-carotene, albumin, uric acid, and bilirubin decreased significantly (p < 0.05) in the probiotic group, only. These alterations led to a significant (p < 0.001) decrease of the average TAC values during the period T1-T3 in both tested groups. In the interval of daily yoghurt consumption (T1-T3) the mean plasma levels of oxidant parameters MDA and CD increased significantly in the probiotic (MDA: p < 0.01; CD: p < 0.001) and the control group (CD: p < 0.01). The average activity of the antioxidant enzyme superoxide dismutase (SOD) was quite constant throughout the study in both groups. The mean activities of GSH-Px and catalase decreased significantly (p < 0.001) in the probiotic group, only after consuming yoghurt daily for four weeks (T1-T3). Although several parameters changed significantly during the study, no significant differences were observed between both investigated groups. Therefore, the results indicate a possible influence of both probiotic and conventional yoghurt on the plasma levels of antioxidant and oxidant parameters.

Organization and Assembly of Metal-Thiolate Clusters in Epithelium-specific Metallothionein-4

Mammalian metallothionein-4 (MT-4) was found to be specifically expressed in stratified squamous epithelia where it plays an essential but poorly defined role in regulating zinc or copper metabolism. Here we report on the organization, stability, and the pathway of metal-thiolate cluster assembly in MT-4 reconstituted with Cd(2+) and Co(2+) ions. Both the (113)Cd NMR studies of (113)Cd(7)MT-4 and the spectroscopic characterization of Co(7)MT-4 showed that, similar to the classical MT-1 and MT-2 proteins, metal ions are organized in two independent Cd(4)Cys(11) and Cd(3)Cys(9) clusters with each metal ion tetrahedrally coordinated by terminal and bridging cysteine ligands. Moreover, we have demonstrated that the cluster formation in Cd(7)MT-4 is cooperative and sequential, with the Cd(4)Cys(11) cluster being formed first, and that a distinct single-metal nucleation intermediate Cd(1)MT-4 is required in the cluster formation process. Conversely, the absorption and circular dichroism features of metal-thiolate clusters in Cd(7)MT-4 indicate that marked differences in the cluster geometry exist when compared with those in Cd(7)MT-1/2. The biological implication of our studies as to the role of MT-4 in zinc metabolism of stratified epithelia is discussed.

On the dynamics of the TPPS4 aggregation in aqueous solutions: Successive formation of H and J aggregates

The dynamics of aggregation of meso-tetrakis (p-sulfonatofenyl) porphyrin (TPPS4) in function of its concentration, pH and ionic strength was studied by optical absorption, fluorescence and resonance light scattering (RLS) techniques. In the region of pH, where TPPS4 exists in biprotonated form, the addition of NaCl induces the TPPS4 aggregation due to the formation of the “cloud” of counter ions around the TPPS4 molecule thus reducing electrostatic repulsion between the porphyrin molecules. The formation of this “cloud” shifts the pKa value to acid region (from 5.0 in the absence of salt to 4.5 at [NaCl]=0.4M), reduces the TPPS4 absorption in all spectral range and quantum yield and lifetime of fluorescence (from 0.27 to 0.17 and from 4.00±0.04 to 3.00±0.03ns in the absence of salt and in the presence of NaCl, respectively). The aggregation process involves two successive stages: initially H aggregates are formed, which in time are transformed in J ones. The existence of these two stages was confirmed by the fluorescence and RLS data. The kinetics of the formation of J aggregates is characterized by the induction time t1 and the average growth time t2, which depend on both TPPS4 and salt concentrations. The induction period t1 appears as a result of initial formation of H aggregates and their successive transformation in J ones. At very high TPPS4 concentrations, the J aggregates are united in more complex structures such as hollow cylinders or helixes.

Neurochemistry of late‐life major depression: A pilot two‐dimensional MR spectroscopic study

To evaluate a two-dimensional localized chemical shift correlated spectroscopy (L-COSY) sequence in elderly patients with major depression. A total of 33 healthy elderly subjects and 15 elderly patients with major depression were investigated. A voxel size of 3 x 3 x 3 cm3 was chosen in the dorsolateral prefrontal region with predominantly white matter, with the use of three slice-selective radiofrequency (RF) pulses (90 degrees , 180 degrees , and 90 degrees). A chemical shift-selective (CHESS) sequence was used prior to volume localization for the presaturation of water. The two-dimensional raw data matrix consisted of 1024 complex points along the detection period (t2), and 100 increments along the evolution period (t1), resulting in a total acquisition time of approximately 27 minutes per acquisition. The metabolite ratios were calculated using the two-dimensional peak volumes with respect to the diagonal peak volume of total creatine (Cr) at 3.0 ppm. In the 33 elderly subjects, the mean ratio of choline (Cho) to Cr was 10% higher in men compared to women (P < 0.05), consistent with earlier findings obtained by one-dimensional MRS. When the metabolite ratios were compared in a subsample of 16 elderly female controls and 12 depressed female patients, the depressed geriatric patients had higher levels of myoinositol (mI), phosphoethanolamine (PE), and glutamate/glutamine (Glx) than the controls, although the differences were not statistically significant. Our pilot study shows the feasibility of performing two-dimensional L-COSY successfully in elderly subjects and patients with late-life mood disorders. These findings are consistent with and expand on our earlier findings in major depressive disorder (MDD) detected with one-dimensional MRS.

Identifying support issues of parents of children with leukemia.

One of the important factors in helping both children with acute lymphoblastic leukemia (ALL) and their family members during the difficult treatment period is the support they receive. However, there is a scarcity of research that examines the adaptation to such an experience from the family's perspective. This discussion presents the findings from recent research on accessing support from the perspective of parents with a child undergoing treatment for ALL. A longitudinal, qualitative study informed by a phenomenological methodology. The results are taken from parent interviews undertaken during the time period from the end of induction-remission to the end of the 5-week period (time period T1), collected over the first year of operation of the study. The need for support was reported as intense, and offers of support tend to lessen over time. Among the sources of support noted were partners, family, friends, employers, hospital staff, and other parents in the same situation. However, community resources appeared to be lacking, underused, or both. Suggestions for support include the provision of practical assistance through appropriately trained volunteers, the involvement of a liaison person to mentor families through the initial stages of treatment, development of parent support groups, and the opportunity for families to meet children who are successfully off treatment. Such support strategies involve sensitivity to particularly vulnerable families who have limited support available and respect for the variation in individual styles of accessing support.

応答スペクトル法による表層地盤の非線形増幅特性の解析法

This paper proposes a response spectrum method (RSM) for evaluating nonlinear amplification of surface strata (SS) overlying an engineering bedrock (EBR). The proposed RSM follows the procedures below. (1) Represent the response characteristics of SS on EBR by a multi-lumped mass model with shear springs and damping coefficients. (2) Calculate a period T1, a mode shape {U1} and a modal damping factor ƒA1 for the first vibration mode. (3) Evaluate the equivalent shear wave velocity Vse of SS. (4) Evaluate the amplification factor R1 of the surface to EBR at T1 using the Haskell matrix of two strata consisting of an equivalent SS with Vse and ƒA1 on EBR. (5) Evaluate the displacements in SS from R1{U1}, and hence evaluate the shear strains. (6) In accordance with nonlinear relations between shear modulus (G), damping factors (h) and shear strains, replace soil constants G and h by those corresponding to strains. (7) Return to step (1) with revised G and h. Iterate these procedures until T1 becomes stable. (8) After T1 is converged, calculate the response distributions in SS. The results obtained by the proposed RSM are compared with those by “SHAKE” in terms of the response spectrum at the surface as well as distributions of displacement, shear wave velocity and damping factor in SS. The applicability of the proposed RSM for evaluating the nonlinear amplification of SS is confirmed through the comparative studies.

Influência do isoflurano na contratilidade miocárdica e fluxo coronariano de corações isolados de ratos

Foram estudados, pela técnica de Langendorff, 18 corações isolados de ratos albinos adultos, submetidos a perfusão retrógrada pela solução de Krebs-Henseleit (pressão de 90 ± 10 cm de H2O, temperatura de 36,5 ± 0,5°C). Os animais foram distribuídos nos seguintes grupos: Grupo I: controle; Grupo II: tratado com isoflurano na concentração de 1,5%. Foram avaliados os seguintes parâmetros: freqüência cardíaca (FC), pressão sistólica (PS), pressão diastólica (PD), dp/dt e fluxo coronariano (FCo). Após 15 min de estabilização, foram obtidos os valores iniciais (t0), sendo os parâmetros registrados seqüencialmente nos seguintes períodos: 1, 2, 4, 6, 10 min. Não ocorreram variações estatisticamente significantes na PS nem na dp no período t1 nos dois grupos estudados. Notou-se aumento da PD (p < 0,05) apenas no Grupo II (4,8 mmHg no período t0, 12,8 mmHg no período t1). Ocorreram ainda diminuição da FC (p < 0,05) e aumento do FCo (p < 0,05) um minuto após a infusão da droga. Notou-se diminuição do FCo de forma progressiva em todos os períodos de recuperação (t2 a t5) após a infusão do isoflurano (p < 0,05). Conclui-se que o isoflurano aumenta o fluxo coronariano durante a sua administração, reduzindo-o no período de recuperação; diminui a freqüência cardíaca e aumenta a pressão diastólica em corações isolados de ratos.

Method of operating a fuel cell

A fuel cell is operated at a temperature which is not greater than substantially 250° C., has an electrolyte which can be a solid polymer electrolyte, a liquid phosphoric acid electrolyte, or a liquid alkaline electrolyte, and a cathode and an anode each comprising a platinum catalyst. Hydrogen fuel gas is supplied to the anode and a gaseous oxidant, for example oxygen is supplied to the cathode. The cathode and anode are both connected to first and second circuits in parallel. The first circuit includes a load to be powered by the fuel cell and a first switch. The second circuit includes a battery and a second switch. The switches are operated by a control. When the first swtich is closed the cell powers the load and the second switch is open. When the first switch is open the second switch is closed so the battery applies a reverse D.C. potential the anode and cathode. The first switch is closed and the second switch is open for a time period T1 which is substantially at least ten times greater than time period T2 for which the first switch is open and the second switch is closed. The time period T2 does not exceed substantially 0.25 seconds. The switches can be relays or solid state electronic switch arrangements.

The influence of changes in hand temperature on the indirectly evoked electromyogram of the first dorsal interosseous muscle.

The evoked EMG response commonly decreases in amplitude during the first few minutes of anaesthesia. The purpose of this study was to determine if a relationship exists between changes in hand temperature, which are known to occur with induction of anaesthesia, and drift in the EMG signal. The indirectly evoked response of the 1st dorsal interosseous muscle was measured using a Datex Relaxograph in 15 patients undergoing elective surgery. The test arm was wrapped in towels in order to minimize heat loss. Core body temperature, hand temperature, and T1 were recorded at two minute intervals for the next 30 min. Patients then received a bolus of mivacurium 0.08 mg.kg-1 and additional doses were given as needed. Complete recovery was defined as a TOF ratio > 0.90. Regression analysis plotting delta temperature against delta T1 was performed for each individual. The slope of the regression line for the relationship between delta degree C and delta T1 was then used to calculate a correction factor (CF) which might be used to "fine tune" the last measured T1. The initial hand temperature averaged 30.8 +/- 1.4 degrees C and this increased by 4.1 +/- 1.2 degrees C over the next 30 min. During this period T1 decreased by 24.8 +/- 5.9% or -6.05%/degrees C. The final mean T1 value at the end of anaesthesia (uncorrected) was 70.6 +/- 7% of control. The average corrected T1 value was 94.7 +/- 8.5% (range, 83-111%). It is concluded that there was a correlation between delta degree C and delta T1 during the first 30 min of anaesthesia (r2 = 0.77, P < 0.0001). However, in 5 of 15 individuals it was not possible to "temperature correct" the final T1 value to within +/- 10% of control. Hence, while changes in muscle temperature probably play a major role in the T1 drift seen with the Datex monitor, other factors remain to be identified.

Minimizing the effects of radio-frequency heating in multidimensional NMR experiments

Application of radio-frequency power in multidimensional NMR experiments can significantly increase the sample temperature compared to that of the surrounding gas flow. Radio-frequency heating effects become more severe at higher magnetic field strengths and ionic strengths. The effects are particularly noticeable for experiments that utilize 1H and/or 13C isotropic mixing and broadband decoupling. If radio-frequency power is applied during the systematically increasing evolution period t1, the sample temperature can change with t1 and thereby cause line-shape distortions. Such distortions are easily avoided by ensuring that the average radio-frequency power remains constant during the entire experiment.

Growth and Yield Performance of Potato Grown at Three Elevations in Hawaii: II. Dry Matter Production and Efficiency of Partitioning

Field data on the growth and yield of potato (Solanum tuberosum L.) are needed for the validation of models of potato growth in tropical environments. A potato genotype ✕ environment experiment was conducted on Mt. Haleakala, Maui, Hawaii, in 1985 at elevations of 91, 282, and 1097 m, and in 1986 at elevations of 91, 640, and 1097 m. The objective was to collect basic data on the effects of environment (primarily temperature) on the patterns of dry matter production and partitioning of the standard north‐temperate cultivats Katahdin, Desiree, Kennebec, and Norchip and the heat‐tolerant clones LT‐I, C14‐343, and CI‐884. Dry weight of plant components and total dry weight per plant (TOT) were measured tuber initiation (T1), T1 + 20 d (T2), and T1 + 40 d (T3). temperatures at 91 m hastened development such that, at T1, TOT was almost 2.0 and 4.0 times greater than at 1097 m for 1985 and 1986, respectively. Overall, tuber dry weight (TU) increased significantly at T2 and T3 as temperature decreased with increasing elevation. Dry matter partitioning to tubers (TU/TOT) generally was highly and significantly correlated with temperature. At T2, 54, 59, 65, and 80% of the variation in TU/TOT for Norchip, Kennebec, Katahdin, and Desiree, respectively, was explained by average minimum temperature from T1 to T2. For the later‐maturing clones LT‐1 and C1‐884, &gt;80% of the variation in TU/TOT also was explained by some measure of temperature during the period T1 to T2, T2 to T3, or both.

Two-dimensional Nutation Echo Nuclear Quadrupole Resonance Spectroscopy

Abstract We discuss two new two-dimensional nuclear quadrupole resonance experiments, both based on the principle of nutation spectroscopy, which can be used to determine the asymmetry parameter, and thus the full quadrupolar tensor, of spin-3/2 nuclei at zero applied magnetic field. The first experiment is a simple nutation pulse sequence in which the first time period (t1) is the duration of the radiofrequency exciting pulse; and the second (t2) is the normal free-precession of a quadrupolar nucleus at zero-field. After double Fourier-transformation, the result is a 2 D spectrum in which the first frequency dimension is the nutation spectrum for the quadrupolar nucleus at zero-field. For polycrystalline samples this sequence generates powder lineshapes; the position of the singularities, in these lineshapes can be used to determine the asymmetry parameters η in a very straightforward manner, η has previously only been obtainable using Zeeman perturbed NQR methods. The second sequence is the same nutation experiment with a spin-echo pulse added. The virtue of this refocussing pulse is that it allows acquisition of nutation spectra from samples with arbitrary inhomogeneous linewidth; thus, asymmetry parameters can be determined even where the quadrupolar resonance is wider than the bandwidth of the spectrometer. Experimental examples of 35Cl, 81Br and 63Cu nutation and nutation-echo spectra are presented.

Two-dimensional zero-field nutation nuclear quadrupole resonance spectroscopy

We introduce a new two-dimensional nuclear quadrupole resonance experiment, in which the first time period (t1) is the duration of the radiofrequency exciting pulse; and the second (t2) is the normal free precession of a quadrupolar nucleus at zero field. After double Fourier transformation, the result is a 2D spectrum in which the first frequency dimension is the nutation spectrum for the quadrupolar nucleus at zero field. For single crystals, this spectrum contains narrow lines, whose frequency, for axially symmetric tensors, is proportional to sin θ, where θ is the angle between the unique axis of the quadrupolar tensor and that of the transmitter/receiver coil. For polycrystalline samples we obtain powder line shapes which are reminiscent of high-field nuclear magnetic resonance (NMR) powder patterns, and which allow determination of the asymmetry parameter η, which has previously only been obtainable using Zeeman perturbed nuclear quadrupole resonance (NQR) methods. Both theoretical spectra and several experimental examples are presented.

Developmental changes in proton magnetic resonance relaxation times of cardiac and skeletal muscle.

Proton magnetic resonance relaxation time measurements were used to study developmental changes in rabbit cardiac and skeletal muscles during the last days of gestation and at several postnatal times. Tissue water content decreased steadily during late fetal and early postnatal stages of development. During this period T1 and T2 for cardiac and skeletal muscles also decreased. The relaxation times stabilized after the 20th postnatal day, and at this juncture the T1 and T2 values for myocardium remained consistently higher than for skeletal muscle. The developmental changes in proton relaxation time probably represent changes in water distribution and mobility as well as macromolecular structure during muscle maturation.

Effect of fulvic and humic acids on nitrificationPart 1: In vitro production of nitrite and nitrate

Abstract Mixed opinions exist on the effect of organic matter on nitrification in soils as well as the lack of data on the effect of fulvic (FA) and humic (HA) acids on this biochemical process. This in vitro investigation was conducted to study the effect of FA and HA on oxidation of NH+ 4 and NO‐ 2 by soil nitrifiers and on the delay period (t') and maximum nitrification rate (Kmax). Soil extracts containing an ammonium‐oxidizer population were incubated in vitro for 3 weeks at 25C in the presence of (NH4)2SO4and 0 to 320 mg FA or HA/L at pH 7.0 or 8.0. A similar experiment was conducted with soil extracts containing a nitrite‐oxidizer population, but with KNO2 as the N source. An additional experiment was conducted with the nitrite‐oxidizer extracts for the determination of t’ and Kmax values. Nitrite production tended to increase linearly as a result of FA and HA treatments from 0 to 320 mg/L at pH 7.0 or 8.0. Fulvic acid appeared to be more effective than HA in increasing the oxidation process. Differences in pH had only a slight effect. On the other hand, nitrate production was decreased linearly by FA or HA treatments from 0 to 320 mg/L which provided some justification for reports of lower nitrate, but higher nitrite concentrations in soils high in organic matter content. Humic acid treatments increased the delay period (t1), and at the same time decreased the maximum nitrification rate (Kmax). The latter suggests that in the presence of HA more time is required to reach a maximum nitrification rate.