Greater Acid Research Articles

Effects of removing sheep grazing on soil chemistry, plant nutrition and forage digestibility: Lessons for rewilding the British uplands

Rewilding is currently being proposed as a means of enhancing the conservation value of marginal land in many parts of the world. This is especially true in the British uplands where rewilding will almost certainly involve either a reduction in livestock grazing, or its complete removal. The aim of reducing stock numbers would be to reverse the degradation of these ecosystems that has been caused by past over‐grazing. However, little is known about the likely outcomes, or the time‐scales over which such ecosystem recovery might occur. Here, we report preliminary results from a recent study of eight sites at Moor House NNR in the north‐Pennines, where permanent plots with‐ and without‐sheep grazing were established between 1954 and 1967 on a range of typical upland plant communities. Soils and vegetation were sampled, and their chemical properties analysed; for vegetation an assessment of the herbage quality for animal nutrition was also made. No significant differences in soil properties, above‐ground biomass and nutritional status of the vegetation was detected that could be attributed to sheep grazing removal. The only significant effect associated with grazing removal was a reduced digestibility of the vegetation (greater acid detergent fibre concentration) where sheep were removed. These results show that a rewilding strategy that relies only on reducing sheep numbers will have very little impact on ecosystem recovery in terms of soil or herbage chemistry over short‐ to medium‐term time‐scales. Rewilding policies, therefore, attempting to restore ecosystems degraded by over‐grazing must, therefore, be viewed as long‐term (>50 y).

Effects of Mining Activities on the Release of Heavy Metals (HMs) in a Typical Mountain Headwater Region, the Qinghai-Tibet Plateau in China.

Understanding the heavy metal (HM) contamination in alpine mountain headwaters regions is important to maintaining the ecosystem stability of the basin. A total of 119 water samples and 104 sediment samples were collected along tributaries and the main course of Heihe River. The concentrations of eight heavy metals (As, Cd, Cr, Cu, Mn, Ni, Pb, and Zn) in water and sediment were measured to describe their spatial variability and to assess water quality. To identify the origins and pathways of HMs, anions, cations, and trace elements, as well as δD/δ18O stable isotopes in water samples were also measured. The results of water quality assessment suggested that tributaries were affected by local mining activity. Factor analysis in sediments showed that all HMs in sediments were inherited from the parent bedrock. Both natural weathering and mining contribute HMs. Cr and Ni were homologous with a source from the weathering of basic gabbro and serpentine at Yushigou. Mn appeared to be influenced more by artificial activities such as agriculture and grazing. Depending on the mining technique involved, two pathways for the release of HMs were distinguished in this area. For open-pit mining, mining promoted the release of HMs primarily via enhanced weathering. For underground mining, HMs might have contributed to greater acid mine discharge at high elevations due to the weak weathering processes. As the elevation decreases, precipitation increases, and a series of complex hydrological factor significantly affect leaching and runoff. The study results can be applied to improve water management efficiency.

Nb-Doped Vanadium Phosphorus Oxide Catalyst for the Aldol Condensation of Acetic Acid with Formaldehyde to Acrylic Acid

Nb-doped vanadium phosphorus oxide catalysts were prepared and characterized using a variety of methods, including XRD, FT-IR, XPS, TPD and BET. The catalysts were examined for their ability to promote the aldol condensation of acetic acid with formaldehyde to acrylic acid. Catalyst composition and the conditions used to prepare the catalysts were investigated for their effects on catalytic activity. The addition of Nb changes the properties and catalytic properties of the catalyst to some extent, especially the surface acidity of catalyst and the average valence of surface V atoms, which have the greatest influence on the catalyst. When Nb/V = 0.06, the catalyst surface has the greatest acidity, the valence of surface V atoms is the lowest, and the selectivity (83.4%) and yield of acrylic acid (18.1%) are maximized.

Using Electron-Transfer-Induced Proton Transfer to Control Binding Strength in H-Bond Dimers

An important goal in supramolecular chemistry is the development of stimuli-responsive systems in which the strength of the intermolecular interactions can be altered by external signals such as changes in light, temperature, pH or voltage of an electrode. Our group is exploring the latter possibility, primarily by trying to develop systems in which electron transfer perturbs the strength of H-bonding interactions between molecules. The underlying principle is straightforward: an oxidation that decreases the negative charge on a H-acceptor (A) or a reduction that decreases the positive charge on a H-donor (D) will weaken a H-bond. Alternatively, reduction that increases the negative charge on a H-acceptor or oxidation that increases the positive charge on a H-donor will increase the strength of a H-bond. However, in the latter case, it is possible that oxidation or reduction could also lead to full proton transfer. If this occurs across the H-bond, the primary H-bonds will remain, but the secondary H-bonds will change. This can lead to an increase in unfavorable secondary interactions, which would counteract the effect of the initial proton transfer. However, with proper design, proton transfer could lead to an increase in favorable secondary interactions, which would enhance the effect of initial transfer. The goal of this project is to do the latter. For this work, the 3 H-bond DAD array, 1, that contains a N-methyl-4,4'-bipyridinium or “monoquat” redox couple (see figure) has been synthesized. Compound 1 forms a three H-bond dimer with the non-electroactive ADA array, 2, in CH2Cl2. Typically, DAD-ADA arrays such as this have relatively weak association constants of ~102 M−1 in non-competitive solvents such as CH2Cl2 due to the three, favorable primary H-bonds (shown as solid, double-headed, green arrows in the figure) being counterbalanced by four unfavorable secondary interactions (shown as dashed, double-headed, red arrows). Preliminary NMR studies suggest stronger binding in this case (>103 M−1), probably due to the greater acidity of the amide NH’s in 1 because of the strongly electron-withdrawing nature of the pyridinium. In the absence of 2, initial cyclic voltammetry studies of 1 display the expected two, sequential, 1 e− reduction waves of the monoquat redox couple in CH2Cl2, corresponding to reduction of 1 to the radical and then the quinoidal anion. Addition of 2 results in no change in the E1/2 of the first reduction, but the second reduction shifts ~0.24 V positive. Further addition of 2 causes no additional change in the E1/2, consistent with a 1:1 complex. The 0.24 V positive shifts indicate a ~104 increase in binding strength upon overall 2 e− reduction of 1. Combined with the initial association constant of >103 M−1, this indicates an association constant of >107 M−1 in the fully reduced state. We believe the most likely explanation of such strong H-bonding in a 3 H-bond array is that the second reduction induces proton transfer across the central H-bond in the complex, thus converting the DAD-ADA array to a DDD-AAA array. The latter is expected to have significantly stronger H-bonding because all of the secondary interactions, in addition to the primary interactions, are favorable. If confirmed by further studies, the association constant in the reduced form would represent, to the best of our knowledge, the largest achieved to date in a redox-dependent H-bonding system, thereby demonstrating the utility of incorporating proton transfer to amplify the effect of electron transfer in these systems. Figure 1

Fish Oil Enzymatic Esterification for Acidity Reduction

The reduction of the fish oil acidity is a significant problem in the rendering industry, as the oil’s range of applications and market value strongly depend on this parameter. In particular, the lower the acidity, the larger the oil’s market value. This work aims to study the potential of enzymatic esterification for reducing the fish oil acidity, by converting the free fatty acids into esters. Thus, four commercial lipases were used and a parametric study was performed to identify the best operating conditions, varying the reaction temperature, enzyme/oil mass ratio and alcohol/FFA mass ratio. All experiments were performed in duplicate with a very good reproducibility of results. Results showed that Lipozyme TL 100L contributed to greater acidity reduction (75% from an initial acid value of 10–14 mg KOH/g oil) for esterification at 40 °C, using ethanol 96% v/v, enzyme/oil and alcohol/FFA mass ratios of 0.01 and 3.24 w/w, respectively, reaching 3.13 mg KOH/g oil of final acid value or 1.57% FFA content. The reaction kinetics were also studied and it was found that a second order rate law as a function of the alcohol and oil concentrations is more adequate, with 35.44 kJ/mol of activation energy and 1.94 × 103 L mol− 1 min− 1 of pre-exponential factor. In conclusion, this work shows that the enzymatic esterification to reduce the fish oil acidity is technically feasible, increasing its market value.

On the Structure of [K(crypt‐222)]+

Due to disorder, [K(crypt‐222)]+ (1) is crystallographically indistinguishable from its isomer, a 1:1 fluoroform clathrate of deprotonated [K(crypt‐222)]+, [K(crypt‐222{‐H+})]·CHF3 (2). In our preceding publications, 1 was characterized on the basis of combined X‐ray diffraction, NMR, reactivity, labeling, acid‐base, and DFT studies. Herein we report that neither incorporation of deuterium nor any other transformation of [K(crypt‐222)]+ is observed in the presence of CD3OD/CD3OK at 70 °C or CD3S(O)CD2K/(D6)DMSO at 23 °C over hours and even days. Since fluoroform is easily and quickly deprotonated under such conditions, the demonstrated greater acidity of CHF3 relative to [K(crypt‐222)]+ provides additional evidence in favor of 1 and against 2. Likewise, crystal packing analysis and DFT calculations support 1, which has now been refined in the ultimately correct space group R32. Our previously drawn conclusions regarding [K(crypt‐222)]+ and the existence of a ‘naked’ trifluoromethyl anion in a condensed phase remain valid. The recent alternative refinement (Becker and Müller, Chem. Eur. J. 2017, 23, 7081 – 7086) of our raw diffraction data has been improperly performed in the wrong space group to yield a non‐charge‐balanced model [K(crypt‐222)]+·CHF3, which is hereby repudiated. Becker and Müller's attempts to resolve the charge balance issue have produced models that are inadequate from the perspective of both crystallography and chemistry.

Property Improvement of α-Amylase from Bacillus stearothermophilus by Deletion of Amino Acid Residues Arginine 179 and Glycine 180.

To improve the properties of α-amylase from Bacillus stearothermophilus (AmyS), a deletion mutant AmyS∆R179-G180 was constructed by deleting arginine (Arg179) and glycine (Gly180) using site-directed mutagenesis. AmyS and AmyS∆R179-G180 were expressed in Bacillus subtilis and purified by ammonium sulfate precipitation, after which the enzymatic properties were characterized and compared. By deleting amino acids Arg179 and Gly180, the thermostability of α-amylase AmyS∆R179-G180 was enhanced and the half-life at 100 °C significantly increased from 24 to 33 min. In addition, AmyS∆R179-G180 exhibited greater acid resistance and lower calcium requirements to maintain α-amylase activity. The secretory capacity of the recombinant strain was evaluated by fed-batch fermentation in a 7.5-litre fermentor in which high α-amylase activity was obtained. The highest activity reached 3300 U/mL with a high productivity of 45.8 U/(mL·h).

Phytoremediation Efficacy of Salix discolor and S. eriocephela on Adjacent Acidic Clay and Shale Overburden on a Former Mine Site: Growth, Soil, and Foliage Traits

Plants regularly experience suboptimal environments, but this can be particularly acute on highly-disturbed mine sites. Two North American willows—Salix discolor Muhl. (DIS) and S. eriocephala Michx. (ERI)—were established in common-garden field tests on two adjacent coal mine spoil sites: one with high clay content, the other with shale overburden. The high clay content site had 44% less productivity, a pH of 3.6, 42% clay content, high water holding capacity at saturation (64%), and high soil electrical conductivity (EC) of 3.9 mS cm−1. The adjacent shale overburden site had a pH of 6.8, and after removing 56.5% stone content, a high sand content (67.2%), low water holding capacity at saturation (23%), and an EC of 0.9 mS cm−1. The acidic clay soil had significantly greater Na (20×), Ca (2×), Mg (4.4×), S (10×), C (12×) and N (2×) than the shale overburden. Foliar concentrations from the acidic clay site had significantly greater Mg (1.5×), Mn (3.3×), Fe (5.6×), Al (4.6×), and S (2×) than the shale overburden, indicating that these elements are more soluble under acidic conditions. There was no overall species difference in growth; however, survival was greater for ERI than DIS on both sites, thus overall biomass yield was greater for ERI than DIS. Foliar concentrations of ERI were significantly greater than those of DIS for N (1.3×), Ca (1.5×), Mg (1.2×), Fe (2×), Al (1.5×), and S (1.5×). There were no significant negative relationships between metal concentrations and growth or biomass yield. Both willows showed large variation among genotypes within each species in foliar concentrations, and some clones of DIS and ERI had up to 16× the Fe and Al uptake on the acidic site versus the adjacent overburden. Genetic selection among species and genotypes may be useful for reclamation activities aimed at reducing specific metal concentrations on abandoned mine sites. Results show that, despite having a greater water holding capacity, the greater acidity of the clay site resulted in greater metal mobility—in particular Na—and thus a greater EC. It appears that the decline in productivity was not due to toxicity effects from the increased mobility of metals, but rather to low pH and moisture stress from very high soil Na/EC.

Contribution of spontaneously-fermented sourdoughs with pear and navel orange for the bread-making

This study investigated the effects of spontaneous sourdoughs started with pear and orange fermentations on the quality attributes of white pan breads, focusing on acidification capacity, fermentation properties, free amino acids (FAA) concentration and bread properties. This work successfully developed that adding sourdough could improve the technological and nutritional properties of the bread, and that different substrates for sourdough led to differences in the bread characteristics. Breads made from sourdough exhibited lower pH (4.66–4.87) and greater acidity (3.95–4.46 mL) than the control breads. It was possible to decrease the gas production by adding sourdough, however, the gas retention ability enhanced evidently. The retention coefficients for pear and navel orange sourdoughs were 87.2% and 90.4%, respectively. Sourdough fermentation supported an appropriate acidic environment for improving the metabolic activity of some endogenous enzymes, resulting in increased specific volume and concentrations of FAAs. The 15 yeasts and 26 LAB isolates from the pear sourdough, the 21 yeasts and 18 LAB isolates from the navel orange sourdough were identified using 16S rRNA gene and 26S rRNA gene sequencing. All LAB isolates were identified as 3 species: Lactobacillus brevis, Lactobacillus plantarum, and Lactobacillus rossiae and all the yeasts as Saccharomyces cerevisiae.

Coupling N-H Deprotonation, C-H Activation, and Oxidation: Metal-Free C(sp3)-H Aminations with Unprotected Anilines.

An intramolecular oxidative C(sp3)-H amination from unprotected anilines and C(sp3)-H bonds readily occurs under mild conditions using t-BuOK, molecular oxygen and N,N-dimethylformamide (DMF). Success of this process, which requires mildly acidic N-H bonds and an activated C(sp3)-H bond (BDE < 85 kcal/mol), stems from synergy between basic, radical, and oxidizing species working together to promote a coordinated sequence of deprotonation: H atom transfer and oxidation that forges a new C-N bond. This process is applicable for the synthesis of a wide variety of N-heterocycles, ranging from small molecules to extended aromatics without the need for transition metals or strong oxidants. Computational results reveal the mechanistic details and energy landscape for the sequence of individual steps that comprise this reaction cascade. The importance of base in this process stems from the much greater acidity of transition state and product for the 2c,3e C-N bond formation relative to the reactant. In this scenario, selective deprotonation provides the driving force for the process.

Gastric Ischemia: An Under-Recognized Cause of Upper GI Bleeding?

A 73-year-old male with coronary artery disease was admitted with progressive dyspnea and multiple episodes of exertional syncope and found to have decompensated heart failure with elevated right heart pressures and moderate pulmonary hypertension by right heart catheterization. Diuresis was initiated. Clinical course was complicated by a persistent hypotension, hemothorax, and bacteremia. Repeat right heart catheterization on hospital day 16 demonstrated normal right heart pressures and mildly elevated pulmonary artery pressures. Sildenafil was started on hospital day 20 to treat pulmonary hypertension. Several hours later, the patient experienced transient syncope with orthostatic hypotension which was attributed to sildenafil. Within 12 hours, the patient had 2 black stools with a decrease in hemoglobin from 11 to 8.8gm/dL, and he was taken for urgent upper endoscopy. This showed a large, confluent area of ulceration with adherent clot and exudate concentrated in the fundus and proximal body with sparing of the antrum. The clinical and endoscopic presentation was consistent with ischemic injury. Repeat upper endoscopy 6 days later re-demonstrated partially healed, confluent ulcerations. Sildenafil was not resumed, and the patient had no further hypotension or gastrointestinal bleeding prior to discharge. Histology revealed no evidence of Helicobacter pylori or malignancy. Gastric ischemia is thought to be uncommon due to the extensive collateral blood supply to the stomach; however, there is reason to think that it is clinically under-recognized. Evaluation of gastric reactance as a measure of tissue ischemia in 100 critically ill adults demonstrated changes consistent with gastric ischemia in 80% of patients irrespective of underlying illness. The clinical syndrome of “stress gastritis” is classically found in the proximal stomach. Several mechanisms have been proposed to explain the greater susceptibility of the fundus and body to ischemic injury. Models of hemorrhagic shock demonstrate increased energy deficits in the fundus and body correlated with increased mucosal ischemic injury; this was potentiated by fasting prior to hemorrhagic insult. Acid exposure and ischemia have an additive effect on the risk of ulcer formation; in the bed bound patient, the fundus will have greater acid exposure due to pooling. Particularly in vasculopaths, gastric ischemia should be considered as a potential cause of upper gastrointestinal bleeding.Figure: Ulcerations in proximal stomach.Figure: Sparing of distal gastric body and antrum.

Fish oil acidity reduction by enzymatic esterification

This work studies the enzymatic esterification for fish oil acidity reduction. Lipozyme TL 100L showed greater acidity reduction (75 %) for esterification at 40 °C, with ethanol 96 %, with enzyme/oil and alcohol/FFA mass ratios of respectively 0.01 and 3.24 w/w, reaching 3.13 mg KOH/g oil of final acid value or 1.57 % FFA content. Lipozyme CALB L showed greater acidity reduction (76 %) for esterification at 45 °C, with ethanol 99.8 %, with enzyme/oil and alcohol/ FFA mass ratios of respectively 0.0045 and 4.92 w/w, reaching 3.33 mg KOH/g oil of final acid value or 1.67 % FFA content.

Comparative study of acid hydrolysis of lignin and polysaccharides in biomasses

Effects of different acid hydrolysis conditions were studied relative to the chemical transformations of lignin in eucalyptus, sugarcane bagasse, and sugarcane straw, and on the transformations of multiple polysaccharides in eucalyptus. The acid hydrolysis using 12 mol/L sulfuric acid followed by acid hydrolysis using approximately 0.41 mol/L sulfuric acid was used as the reference for the lignin and sugar analysis. During acid hydrolysis, the relative amount of lignin increased with longer reaction times and/or greater acid concentrations for all biomasses. The overestimation of lignin in harsher acidic conditions resulted from the summation of lignocellulosic-derivatives (pseudo-lignin) together with lignin itself. Lignin reactions (dissolution/deposition) for bagasse and straw occurred in a greater extent than for eucalyptus, considering similar conditions of acid hydrolysis. The sugar transformation during acid hydrolysis was also investigated for eucalyptus. The sugar content quantified in eucalyptus decreased as the acid concentration and/or reaction time in the second hydrolysis increased. Glucose, galactose, and mannose were more resistant to harsher acidic conditions than xylose and arabinose. However, the most severe conditions (121 ºC, 90 min, and 6.15 mol/L H2SO4) caused complete sugar degradation.

Vonoprazan 10 mg daily is effective for the treatment of patients with proton pump inhibitor-resistant gastroesophageal reflux disease.

Gastroesophageal reflux disease (GERD) is commonly treated by primary care physicians. Although proton pump inhibitors (PPI) have been the mainstay of GERD treatment for two decades, in some patients GERD is refractory to standard dose PPI for more than eight weeks and is referred to as PPI-resistant GERD. Vonoprazan, a novel competitive acid blocker, became available in Japan for the treatment of patients with GERD, and has greater acid inhibition than existing PPIs. The aim of the present study was to determine the effect of vonoprazan 10 mg daily on PPI-resistant GERD. We retrospectively reviewed 24 patients with PPI-resistant GERD treated with vonoprazan 10 mg daily. The Izumo scale was used to evaluate the effect of vonoprazan before and one month after treatment, which reflects quality of life related to gastrointestinal symptoms. The overall rates of improvement and resolution of GERD symptoms were 88% (21/24) and 42% (10/24), respectively, and the score was significantly decreased (before 5.8±1.7, at one month 1.9±1.9, P<0.001). To evaluate the influence of esophageal erosions despite prior PPI treatment, the patients were divided into erosive (n=6) and non-erosive groups (n=18). Vonoprazan achieved 100% (6/6) improvement in the erosive group and 83% (15/18) in the non-erosive group. Patients in the erosive group had a significantly higher rate of resolution than in the non-erosive group [83% (5/6) vs 28% (5/18), P=0.017]. No adverse events occurred. Other GI symptoms in patients with PPI-resistant GERD were evaluated. The scores for epigastric pain, postprandial distress, constipation and diarrhea were unchanged during the treatment period. In conclusion, vonoprazan 10 mg daily is effective for the treatment of patients with PPI-resistant GERD. Vonoprazan resolves GERD symptoms in patients with erosions more than in those without erosions. This is the first report on the effect of vonoprazan 10 mg on PPI-resistant GERD.

Double-Pruning Grapevines as a Management Tool to Delay Berry Ripening and Control Yield

Sangiovese vines mechanically spur-pruned during dormancy in February were manually finished either immediately or post budburst to test the potential of a ‘double-pruning’ approach to delay fruit sugar accumulation and limit yield. The treatments were applied in 2014, 2015, and 2016 at BBCH-0 as standard hand-finishing on dormant buds (SHF), and as late (LHF) and very late (VLHF) hand-finishing at BBCH-14 and BBCH-19, i.e., when the two apical shoots on the mechanically-shortened canes were ~10 and 20 cm long, respectively. While yield per vine was drastically reduced in the VLHF treatment (−43% versus SHF) due to high incidence of unsprouted (blind) nodes, lower shoot fruitfulness, and berries per cluster, yield reduction in LHF was −22% versus SHF due only to the incidence of unsprouted nodes. While the fruit ripening profile was not significantly modified in VLHF compared to SHF, in data pooled over three seasons, LHF delayed basic fruit composition at harvest, producing fruit with less total soluble solids, lower pH, and greater acidity, but more phenolics than SHF. Overall, LHF proved to be effective at reducing yield per vine to a level that did not require expensive cluster thinning. By reducing berry sugar accumulation, it has the potential to produce wines with lower alcohol and higher phenol content. Noteworthy too is its potential to delay harvest date or increase crop hanging time under specific vineyard conditions.

Comparison of oesophageal function tests between Chinese non-erosive reflux disease and reflux hypersensitivity patients

BackgroundBy means of 24 h multi-channel intraluminal impedance and pH recording (MII/pH), patients with heartburn and normal upper gastrointestinal endoscopy findings can be classified into those with non-erosive reflux disease (NERD) and those with reflux hypersensitivity (RH). Therefore, in this study, we investigated the difference in oesophageal function tests in Chinese patients with NERD and RH.MethodsNERD patients were selected from the digestive department, Beijing Anzhen Hospital and Beijing Chao-Yang Hospital, Capital Medical University, after upper gastrointestinal endoscope, high-resolution manometry and impedance (HRiM), and MII/pH examinations between 2014 and 2016.ResultsIn total, 111 NERD patients with abnormal acid exposure, and 92 RH patients were enrolled. Values for NERD and RH were as follows: lower oesophageal sphincter pressure, 15.3 ± 8.9 and 19.3 ± 23.3 mmHg (P = 0.122); integrated relaxation pressure, 7.5 ± 4.8 and 7.9 ± 5.2 mmHg (P = 0.485); distal contractile integral, 751.9 ± 856.2 and 661.9 ± 961.7 mmHg∙s∙cm (P = 0.482); ineffective oesophageal motility rate, 49.5% and 41.3% (P = 0.241); fragmented peristalsis rate, 5.4% and 9.8% (P = 0.235); hiatal hernia rate, 9.0% and 8.6% (P = 0.938); total bolus transit time, 6.3 ± 1.3 and 6.5 ± 1.3 s (P = 0.119); complete bolus transit rate, 76.1 ± 33.0% and 73.1 ± 32.0% (P = 0.224); total acid exposure time, 6.1 ± 3.7% and 0.8 ± 0.8% (P < 0.001); total bolus exposure time, 2.5 ± 2.1% and 1.5 ± 1.1% (P < 0.001); proximal acid reflux events, 13.2 ± 10.5 and 9.7 ± 8.9 (P = 0.011); distal acid reflux events, 25.3 ± 15.8 and 13.4 ± 11.2 (P < 0.001); post-reflux swallow-induced peristaltic wave index, 25.1 ± 9.5% and 32.6 ± 15.2% (P < 0.001); and mean nocturnal baseline impedance, 1,450.2 ± 750.8 and 2,503.6 ± 964.1 ohms (P < 0.001), respectively.ConclusionsNERD and RH patients showed similar values on HRiM. NERD patients had greater acid exposure time, bolus exposure time, proximal and distal acid reflux events, and increased impairment of chemical clearance and mucosal integrity than RH patients. NERD and RH should be classified correctly by MII/pH to provide adequate relief from related symptoms.

Waste Rock Biogeochemistry in a Permafrost Environment: Examination of a Cover Design for a Low-Sulfide, Granitic Waste Rock

ABSTRACTAt the Diavik Waste Rock Project's mine-research site, the microbial colonization and oxidation of waste rock sulfide minerals are attenuated by the extreme freeze-thaw cycle of a permafrost environment. The closure design for the waste rock stockpile consists of a low-sulfide waste rock and low-permeability till, covering a relatively higher sulfide waste rock. This design was examined at the mine site through construction of experimental waste rock piles and active zone lysimeters with and without the till cover. Leachate from these experiments indicates variable pH and SO4 concentrations that correlate with sulfide content and the thermal moderating influence of the till cover. The till initially provided a moderated environment for the production of acid, growth of acidophilic Fe- and S-oxidizing bacteria, and enhanced weathering until wet up and freezing of the till and underlying waste rock as a permafrost. Greater sulfide oxidation was observed above the till cover because of greater exposure to the annual freeze-thaw cycle. An examination of the bacterial communities at the genus level indicates the prevalence of Pseudomonas, Rhodanobacter, Sideroxydans, and Thiobacillus in the waste rock. Pseudomonas spp. were dominant in the drier and more extreme temperature environment above the till cover, while Thiobacillus spp. were dominant in the more sulfide-rich, wetter/frozen environment below the till. A decreasing trend in Thiobacillus spp. from the exterior to the interior and an opposing trend in Acidithiobacillus spp. suggest greater acid generation deeper in the waste rock further from the extreme temperature variation of the tundra climate. The presence of the till cover moderated temperature variations, enhanced the initial rate of sulfide oxidation, and allowed for greater microbial diversity, but the freezing of the till cover and underlying waste rock drastically reduced sulfide oxidation and the generation of acid rock drainage. These results highlight the importance of temperature on microbially catalyzed acid production and our ability to use the extreme temperatures of the tundra climate to minimize potential environmental effects from mining through formation of waste rock permafrost.

Inhibitory Effects of Nitrite on Acid Production in Dental Plaque in Children.

To assess the inhibitory effects of nitrite on plaque acidogenicity and its relationship with caries experience. Plaque (2 μl) was collected from 76 children (age 5.8 ± 2.6 years, dmft 2.9 ± 3.5, DMTF 0.6 ± 1.4) and mixed with nitrite solution (final concentration = 0.63 mM) or distilled water (control). The initial pH (pH-0) of each sample was measured using a portable pH meter. The samples were incubated for 10 min, then their pH (pH-1) was measured again. Next, glucose (final concentration = 0.67%) was added to the samples, which were then incubated for a further 10 min before their pH was assessed for a third time (pH-2). The pH-0, pH-1, and pH-2 values of the control samples were 7.25 ± 0.16, 6.07 ± 0.44, and 5.11 ± 0.48, respectively, and those of the nitrite-treated samples were 7.26 ± 0.16, 6.37 ± 0.45, and 5.34 ± 0.48, respectively. The pH-1 and pH-2 values of the nitrite-treated samples were higher than those of the control samples (p < 0.005). Greater plaque acid production was associated with stronger inhibition of plaque acid production by nitrite (p < 0.005). No relationship was detected between the inhibition by nitrite and caries experience. Nitrite inhibited both endogenous and exogenous plaque acid production. Nitrite inhibited acid production more markedly in plaque that exhibited greater acid production, suggesting that nitrite might be effective at preventing caries, as it contributes to pH homeostasis in plaque by countering excess acidification.

Soil fertility constraints and yield gaps of irrigation wheat in South Africa

&#x0D; &#x0D; &#x0D; South Africa currently faces a wheat (Triticum aestivum L.) crisis as production has declined significantly over the past few years. The objective of this study was to explore opportunities for improving yields in intensive irrigated wheat production systems of South Africa through analyses of yield gaps, soil fertility constraints and conservation agriculture practices. The study was conducted in the major irrigation wheat production areas across four geographical regions: KwaZulu-Natal, eastern Highveld, warmer northern and cooler central. Actual yield (Ya) based on long-term yield data ranged from 5.99±0.15 t/ha to 8.32±0.10 t/ha across different geographical regions. The yield potential (Yp) ranged from 7.57 t/ha to 11.45 t/ha. Yield gaps (Yp–Ya) were in the range of 1.58–3.13 t/ha. Yields could be increased by 26–38% through closing yield gaps. On 88.37% and 13.89% of the fields in the KwaZulu-Natal and warmer northern regions, respectively, there was strong evidence of the practise of conservation agriculture, but none in the other regions. On 42.31% of irrigated wheat fields, soil organic carbon was below 1% at a soil depth of 0–20 cm. Fields in which conservation tillage was practised had double the soil organic carbon of conventionally tilled fields (2.15±0.10% versus 1.02±0.05%), but greater acidity and phosphorus deficiency problems. Sustainable approaches for addressing phosphorus deficiency and acidity under conservation tillage practices need to be sought, especially in the KwaZulu-Natal region.&#x0D; &#x0D; &#x0D; &#x0D; &#x0D; Significance: &#x0D; &#x0D; &#x0D; &#x0D; Opportunities for improving wheat yields in South Africa need to be explored to address the wheat crisis.&#x0D; Sustainable approaches for addressing phosphorus deficiency and acidity of soil under conservation tillage practices need to be sought, especially in the KwaZulu-Natal region.&#x0D; &#x0D; &#x0D; &#x0D;

Evaluation of Diverse Soybean Germplasm for Forage Yield and Quality Attributes

Information on biomass yield and forage nutritive value of grain‐ and forage‐type soybean [Glycine max (L.) Merr.] cultivars is of interest to livestock and row‐crop farmers. We studied grain and forage genotypes for biomass, forage nutritive value, and seed yield across two Arkansas locations over 2 yr. Results revealed that stem and total biomass at the R1 (beginning bloom) reproductive growth stage were significantly greater in forage genotypes than in grain genotypes. Forage genotypes had a greater amount of stem biomass (208.7 and 484.0 g m−2) at both R1 and R6 stages and leaf biomass (246.2 g m−2) at R1 than grain genotypes (140.4, 309.2, and 243.8 g m−2, respectively). At R6, grain genotypes had greater amounts of leaf (388.3 g m−2) and pod biomass (350.5 g m−2) than forage genotypes (350.4 and 272.5 g m−2, respectively). There were no differences in leaf and total biomass between forage and grain genotypes at R6. Grain genotypes showed significantly greater seed yield than the forage genotypes (2662.3 vs. 1320.2 kg ha−1), but no differences in seed protein and oil. Forage genotypes had less crude protein and greater acid detergent fiber than grain genotypes, while their neutral detergent fiber concentrations varied among growth stages. Forage soybeans had lower forage nutritive value than grain soybeans overall. For the southern latitude of Arkansas and southern states, we recommend the late‐maturing forage genotypes ‘Tyrone’ and ‘SG13–53’ and grain genotypes ‘Arksoy’ and ‘Centennial’ for planting as forage crops. Our results provide valuable information to growers of these distinctly different soybean types.