A global pandemic and two hurricanes in two weeks. That's enough disaster to daunt even the staunchest college officials. But the leadership team and staff at SOWELA Technical Community College met ...the challenges, building on a retention rate of 75.06% from spring to fall 2020, to achieve an 83.71% retention rate from fall 2020 to spring 2021, the highest of any community college in Louisiana.
Formation of Fe(II)-As(III) solids is suspected to limit dissolved As concentrations in anaerobic environments. Iron(II) precipitates enriched in As(III) have been observed after microbial reduction ...of As(V)-loaded lepidocrocite (γ-FeOOH) and symplesite (Fe(II)^sub 3^(As(V)O^sub 4^)^sub 2^·8H^sub 2^O) and upon abiotic reaction of Fe(II) with As(III). However, the conditions favorable for Fe(II)-As(III) precipitation and the long-term stability (relative to dissolution) of this phase are unknown. Here we examine the composition, local structure, and solubility of an Fe(II)-As(III) precipitate to determine environments where such a solid may form and persist. We reveal that the Fe(II)-As(III) precipitate has a composition of H^sub 7^Fe^sub 4^(AsO^sub 3^)^sub 5^ and a log K^sub so^ of 34 for the dissolution reaction defined as: H^sub 7^Fe^sub 4^(AsO^sub 3^)^sub 5^ + 8H^sup +^ = 4Fe^sup 2+^ + 5H^sub 3^AsO^sub 3^. Extended X-ray absorption fine structure spectroscopic analysis of H^sub 7^Fe^sub 4^(AsO^sub 3^)^sub 5^ shows that the molecular environment of Fe is dominated by edge-sharing octahedra within an Fe(OH)^sub 2^ sheet and that As is dominated by corner-sharing As^sup III^O^sub 3^ pyramids, which are consistent with previously published structures of As(III)-rich Fe(II) solids. The H^sub 7^Fe^sub 4^(AsO^sub 3^)^sub 5^ solid has a pH-dependent solubility and requires millimolar concentrations of dissolved Fe(II) and As(III) to precipitate at pH <7.5. By contrast, alkaline conditions are more conducive to formation of H^sub 7^Fe^sub 4^(AsO^sub 3^)^sub 5^; however, a high concentration of Fe(II) is required, which is unusual under alkaline conditions.
Category:
Ankle, Ankle Arthritis, Hindfoot
Introduction/Purpose:
A variety of operative approaches and fixation techniques have been described for tibiotalar (TT) and tibiotalocalcaneal (TTC) ...arthrodesis. In the past two decades, authors have begun to more robustly examine outcomes of the transfibular approach for TT arthrodesis and expanded its indication to include TTC fusion. The transfibular technique is broadly divided into two categories: 1) Complete excision of fibula 2) Soft tissue preservation techniques with retention of fibula. The purpose of this study was to retrospectively assess the surgery outcomes in transfibular approach and compare the fibula excision versus fibula retention techniques and examine the factors that play into the risk.
Methods:
Following institutional review board approval, a retrospective review was performed on all patients who underwent TT and TTC arthrodesis through a lateral transfibular approach with minimum 1 year clinical and radiologic follow up. All other operative approach and fixation combinations for arthrodesis were excluded. Primary outcomes examined were union rate, revisions, and complications related to fibula excision versus retention group. Sixteen patients underwent TT and TTC arthrodesis with fibular retention and twelve with fibular excision techniques.
Results:
The overall union rate was 89%, 87% (14 of 16 ankles) for the fibula retention group, and 91% (11 of 12) for fibula excision group (P = .72). Symptomatic nonunion requiring revision arthrodesis occurred in 6% (1 of 16) of the retention group versus 8% (1 of 12) in the excision group (P = .83). There were no significant differences in individual tibiotalar or subtalar union, reoperation, superficial wound problems, infection and symptomatic hardware rates. Elective hardware removal was performed in 12%(2of 16) in fibular retention group versus 25%(3 of 12) in fibula excision group (P = .39), none of the hardware removal was related to the fibula fixation. Each group had three episodes of reoperation due to non-union, osteomyelitis and painful hardware.
Conclusion:
Union, reoperation rates were similar in fibula resection versus retention groups. The frequency of infection and wound complication was not significantly different in both groups, despite the wide variety of patient population and preoperative indications.
Meeting food/wood demands with increasing human population and per‐capita consumption is a pressing conservation issue, and is often framed as a choice between land sparing and land sharing. Although ...most empirical studies comparing the efficacy of land sparing and sharing supported land sparing, land sharing may be more efficient if its performance is tested by rigorous experimental design and habitat structures providing crucial resources for various species—keystone structures—are clearly involved. We launched a manipulative experiment to retain naturally regenerated broad‐leaved trees when harvesting conifer plantations in central Hokkaido, northern Japan. We surveyed birds in harvested treatments, unharvested plantation controls, and natural forest references 1‐year before the harvest and for three consecutive postharvest years. We developed a hierarchical community model separating abundance and space use (territorial proportion overlapping treatment plots) subject to imperfect detection to assess population consequences of retention harvesting. Application of the model to our data showed that retaining some broad‐leaved trees increased the total abundance of forest birds over the harvest rotation cycle. Specifically, a preharvest survey showed that the amount of broad‐leaved trees increased forest bird abundance in a concave manner (i.e., in the form of diminishing returns). After harvesting, a small amount of retained broad‐leaved trees mitigated negative harvesting impacts on abundance, although retention harvesting reduced the space use. Nevertheless, positive retention effects on the postharvest bird density as the product of abundance and space use exhibited a concave form. Thus, small profit reductions were shown to yield large increases in forest bird abundance. The difference in bird abundance between clearcutting and low amounts of broad‐leaved tree retention increased slightly from the first to second postharvesting years. We conclude that retaining a small amount of broad‐leaved trees may be a cost‐effective on‐site conservation approach for the management of conifer plantations. The retention of 20–30 broad‐leaved trees per ha may be sufficient to maintain higher forest bird abundance than clearcutting over the rotation cycle. Retention approaches can be incorporated into management systems using certification schemes and best management practices. Developing an awareness of the roles and values of naturally regenerated trees is needed to diversify plantations.
日本語要旨
人口と一人当たりの消費の増加に伴う食糧・木材需要を満たすのは差し迫った保全上の課題で、土地の節約と共有の二者択一という形でとらえられることが多い。土地の節約と共有の有効性を比較した実証研究の多くは土地の節約を支持しているが、頑健な実験計画で性能を検証し、様々な種類にとって重要な資源を提供する生息地構造—キーストーン構造—を明確に関与させると、土地の共有はより効率的になる可能性がある。そこで私たちは北海道中部で針葉樹人工林を伐採して収穫する際に天然更新した広葉樹を保持する操作実験を開始した。伐採処理区、非伐採の人工林対照区、天然林参照区において伐採一年前と伐採後3年間、鳥類調査を実施した。不完全な発見の下で保持伐採の個体群への帰結を調査するために、個体数と空間利用(実験区と重なる縄張りの割合)を分離する階層群集モデルを開発した。得られたデータにモデルを当てはめたところ、少量の広葉樹の保持は森林性鳥類の総個体数を伐採周期を通して増加させたことが示された。具体的には、伐採前の調査から広葉樹の量は森林性鳥類の個体数を上に凸型(効用逓減の形状)に増加させた。伐採後は、少量の保持された広葉樹は個体数への伐採の負の影響を軽減した。ただし保持伐採は空間利用を減少させた。それにも関わらず、個体数と空間利用の積である鳥類の伐採後の密度に正の保持効果が及ぼす影響は上に凸型を示した。すなわち、少量の収益の減少は森林性鳥類の個体数の大きな増加を生み出すことが示された。皆伐と少量の広葉樹保持の間の鳥類個体数の差異は伐採後一年目から二年目にかけてわずかに増加した。私たちは針葉樹人工林の管理にとって少量の広葉樹の保持は費用対効果の高いオン・サイト(人工林内)の保全の取り組みかもしれないと結論付ける。haあたり20‐30本の広葉樹の保持は伐採周期を通じて皆伐よりも多くの森林性鳥類の個体数を維持するために十分であるかもしれない。保持の取り組みは認証制度やガイドラインを用いることによって管理体系に組み込むことができる。人工林を多様化させるためには天然更新した樹木の役割や価値に関する認知度を高める必要がある。
•Effects of tree retention on ectomycorrhizal fungal (EcMf) diversity were surveyed.•Conifer aggregated retention retained EcMf in the unharvested conifer plantations.•Broadleaved dispersed retention ...retained different EcMf from the conifer plantations.•Conifer seedlings shared ectomycorrhizal fungi with the retained broadleaved trees.•Tree retention mitigated the impacts of logging on EcMf diversity.
We have examined the effects of dispersed and aggregated retention on the diversity of root-associated ectomycorrhizal fungi (EcMf) in Sakhalin fir (Abies sachalinensis) plantations, 4 years after logging. Roots of Sakhalin fir seedlings and the adjacent broadleaved or Sakhalin fir trees were sampled in broadleaved dispersed retention sites (10, 50, or 100 trees/ha), conifer aggregated retention sites (a single 60 × 60 m square patch of Sakhalin fir trees per site), clear-cut sites, unharvested Sakhalin fir plantations, and natural broadleaved forest stands. The EcMf on the roots were grouped into operational taxonomic units based on the similarity of the internal transcribed spacer sequences within the nuclear ribosomal DNA. Clear-cutting significantly reduced the species richness and diversity of the EcMf and altered the species composition when compared with the unharvested Sakhalin fir plantations and natural broadleaved forests. In contrast, both the aggregated and dispersed retention sites maintained higher levels of EcMf diversity, as well as different EcMf communities when compared with the clear-cut sites. Aggregated retention was effective at conserving EcMf diversity at the unharvested Sakhalin fir plantations, but the effects were limited within retained patches. Broadleaved dispersed retention did not retain the EcMf communities that were present prior to logging even at high retention levels, but they could retain unique EcMf communities, which differed between the Sakhalin fir plantations, natural broadleaved forests, and clear-cut sites. The species richness and diversity values for some of the dispersed retention sites were comparable to the values for the unharvested Sakhalin fir plantations and tended to be greater than the values for the aggregated retention sites. The results indicate that dispersed retention could be an effective strategy by which to preserve a larger number of EcMf species and unique EcMf communities in logged conifer plantations, although the positive effects were likely limited spatially within the rooting zones of the retained broadleaved trees. Finally, naturally regenerating Sakhalin fir seedlings were found to share a large amount of their EcMf with adjacent broadleaved retention trees, indicating that multi-host EcMf of retained trees largely contribute to ectomycorrhizal colonization of the surrounding regenerated seedlings in the logged areas. Our findings demonstrated that both dispersed and aggregated retention methods could be used to mitigate the impacts of logging on EcMf diversity in Sakhalin fir plantations, in Japan, and that there were large differences in the effects among the different retention methods.
1. Variable-retention harvest is widely recognized as an alternative to more intensive methods such as clear-cutting. However, present information is inadequate to judge the impact of variable ...retention on biodiversity of indigenous forest organisms intolerant of canopy removal, such as forest-inhabiting bryophytes. 2. We examined how bryophyte species cover, richness, diversity and composition change with time in response to a broad range of dispersed retention harvest treatments (2% clear-cut, 10%, 20%, 50%, 75% retention of original basal area) contrasted with uncut controls 100% retention) in broadleaf deciduous, mixedwood and conifer-dominated boreal forests in North West Alberta, Canada. Bryophytes were studied in 432 permanent sample plots within 72 compartments before harvest and at 3, 6 and 11 years after harvest. 3. Clear-cut and lower (10% and 20%) retention levels resulted in lower cover and richness of bryophytes than in unharvested control compartments in mixed and conifer-dominated forests, but less so in deciduous-dominated forests, which generally supported low cover and richness. Species composition in each forest type varied along the gradient of harvesting intensity; clear-cuts and lower levels of retention supported similar composition, as did control plots and those representing higher retention levels. Over time, the retention harvest treatments became more similar to uncut controls. 4. Synthesis and applications. Variable-retention harvests can better maintain bryophyte biodiversity in managed boreal mixedwood forests, as compared to clearcuts. We found the efficacy of retention harvest scaled with harvest intensity. Higher levels of retention better moderated the negative impacts of harvesting on bryophyte assemblages across all forest types. Our results suggest, however, that even 10% retention will facilitate faster post-harvest recovery of bryophytes, as compared to clear-cutting.
•Development of electrostatic retention model in mixed-mode liquid chromatography.•The model accurately predicted the retention of charged solutes at different pH.•Characterizing the phase system by ...acquiring single component adsorption isotherm.•Development of implicit electrostatic competitive adsorption isotherm model.•The model accurately predicted the competitive elution profiles for two components.
This study investigated the influence of pH on the retention of solutes using a mixed-mode column with carboxyl (-COOH) groups acting as weak cation exchanger bonded to the terminal of C18 ligands (C18-WCX column) and a traditional reversed-phase C18 column. First, a model based on electrostatic theory was derived and successfully used to predict the retention of charged solutes (charged, and ionizable) as a function of mobile phase pH on a C18-WCX column. While the Horváth model predicts the pH-dependent retention of ionizable solutes in reversed-phase liquid chromatography (RPLC) solely based on solute ionization, the developed model incorporates the concept of surface potential generated on the surface of the stationary phase and its variation with pH. To comprehensively understand the adsorption process, adsorption isotherms for these solutes were individually acquired on the C18-WCX and reversed-phase C18 columns. The adsorption isotherms followed the Langmuir model for the uncharged solute and the electrostatically modified Langmuir model for charged solutes. The elution profiles for the single components were calculated from these isotherms using the equilibrium dispersion column model and were found to be in close agreement with the experimental elution profiles. To enable modelling of two-component cases involving charged solute(s), a competitive adsorption isotherm model based on electrostatic theory was derived. This model was later successfully used to calculate the elution profiles of two components for scenarios involving (a) a C18 Column: two charged solutes, (b) a C18 Column: one charged and one uncharged solute, and (c) a C18-WCX Column: two charged solutes. The strong alignment between the experimental and calculated elution profiles in all three scenarios validated the developed competitive adsorption model.
Purpose The AUA (American Urological Association) QIPS (Quality Improvement and Patient Safety) committee created a white paper on the diagnosis and management of nonneurogenic chronic urinary ...retention. Materials and Methods Recommendations for the white paper were based on a review of the literature and consensus expert opinion from the workgroup. Results The workgroup defined nonneurogenic chronic urinary retention as an elevated post-void residual of greater than 300 mL that persisted for at least 6 months and documented on 2 or more separate occasions. It is proposed that chronic urinary retention should be categorized by risk (high vs low) and symptomatology (symptomatic versus asymptomatic). High risk chronic urinary retention was defined as hydronephrosis on imaging, stage 3 chronic kidney disease or recurrent culture proven urinary tract infection or urosepsis. Symptomatic chronic urinary retention was defined as subjectively moderate to severe urinary symptoms impacting quality of life and/or a recent history of catheterization. A treatment algorithm was developed predicated on stratifying patients with chronic urinary retention first by risk and then by symptoms. The proposed 4 primary outcomes that should be assessed to determine effectiveness of retention treatment are 1) symptom improvement, 2) risk reduction, 3) successful trial of voiding without catheterization, and 4) stability of symptoms and risk over time. Conclusions Defining and categorizing nonneurogenic chronic urinary retention, creating a treatment algorithm and proposing treatment end points will hopefully spur comparative research that will ultimately lead to a better understanding of this challenging condition.
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