深さ優先ヒューリスティック探索によるソフトウェアモデル検査効率化

モデル検査技術は，対象とするモデルが取りうる全状態を網羅的に探索し，モデルが満たすべき性質への適合を調べることで，モデルの正しさを検証する技術である．近年では，実装コードそのものを扱うソフトウェアモデル検査技術が注目されている．本論文で扱うJava PathFinder (JPF) は，Java プログラムを対象としたモデル検査器であり，プログラム中の不具合の検出や，プログラムの正しさの検証に利用することができる．ソフトウェアモデル検査技術は，テスト工程における不具合検出に有効である．通常のテストは，想定される様々な入力や環境パラメータに対してプログラムを動作させることで，不具合を洗い出す．しかしながらテストにおいては，非決定的にプログラムが実行される部分があり，必ずしも不具合が発生する状況を再現することができない．例えば，並行プログラムにおいて，複数のスレッドが特定の順序で実行された場合に発生する不具合は，その再現がスレッドの実行順序という非決定要因に依存するため，テストおいて再現できない場合が発生する．これに対して，ソフトウェアモデル検査では，そのような非決定的要因について，全ての選択肢を試行することで，取りうる全てのプログラム状態を再現することで，不具合の発見漏れを防ぐことが可能となる．しかし，モデル検査技術は，モデルの取りうる状態を全て探索するため，モデルの規模に応じて，探索すべき状態数が指数的に増加し，現実的な時間で検証が終了しないという状態爆発への対応が課題となる．とくにソフトウェアモデル検査では，プログラムという抽象度の低いモデルを対象とするため，この状態爆発の問題が顕著である．そこで，この課題を解決する手法として優先度に基づくヒューリスティック探索手法が提案されている．ヒューリスティック探索では，各探索状態について，その先に不具合の含まれる見込みが高いと思われる状態から優先的に探索を進めることによって，不具合の発見を早期化することを目的としている．本研究の対象とするJPF においても探索アルゴリズムとして選択可能である．しかし，従来のヒューリスティック探索には二つ課題があった．一つは，優先度を算出するためのヒューリスティックを適切に選択しないと，優先度が均一となり，横方向に広く探索を行うことになり，探索空間の深いところに到達しづらいという点である．もう一つは，活性等の検証に用いるLinear Temporal Logic (LTL) 検証の実装に適さないという点である．LTL 検証に広く活用されているアルゴリズムは，深さ優先探索をベースとしたものである．これに対して，ヒューリスティック探索は，探索空間中を任意の順序で探索するため，深さ優先ベースのLTL 検証と組み合わせることが困難である．そこで本研究では，従来手法と異なる考え方に基づくヒューリスティック探索手法を提案する．従来手法は，各状態に対して，その先，不具合に至る可能性の高さを見積もり，探索順序を決定する「優先順序付け」探索である．これに対して提案手法は，優先度付けは行わず，探索順序は深さ優先のままとし，その代わりに，不具合に至る見込みが低いと判断した場合に，その先の枝の探索を打ち切る「枝刈り」探索である．提案手法をDepth First Heuristic Search (DFHS) と呼ぶ．従来手法の優先度の算出および，DFHS の枝刈りの判定は，いずれも各状態におけるヒューリスティックによって決定する．例えば，実行パスにおける各スレッドのインターリーブの状態が代表的な指標である．さらにDFHS では，探索順序は深さ優先ではあるものの，各状態から遷移可能な枝が複数存在する場合に，その状態からどの枝に遷移するかについてのみ順序制御可能とする．このときの指標も，例えばできるだけインターリーブが発生するような枝を先に選ぶ，といった観点で指定する．枝刈りのヒューリスティックと組み合わせることで，複合的な効果が期待できる．従来手法とDFHS は，ある意味でコインの両面であり，どちらの方式が有利であるか(あるいはどちらも有効でないか) は，探索空間における不具合状態の分布によって異なると考えられるため，従来手法が苦手としていた探索空間で，DFHS が有効にはたらく可能性がある．本研究では，JPF の機能拡張機構を活用してDFHS を実装し，手法の検証を行った．DFHS は，深さ優先探索を基本としているため，LTL 検証アルゴリズムにも適用可能である．そこで本研究では，LTL 検証についてもDFHS の適用を行った．JPF はアサーションの確認，未捕捉例外の発生，デッドロックなどの安全性の検証を主眼としており，標準では活性の検証をサポートしていない．そこで，活性等の検証を可能とするために，LTL 検証のための探索エンジンを実装した．LTL 検証は，対象とするプログラムが，LTL 式で表された活性等の性質を満たすかどうかを検証する．LTL 式をBAijchi オートマトンに変換したものと，プログラムの状態空間を掛け合わせた同期積に対して探索を実施するため，安全性検証よりもさらに大きな状態空間の探索となる．LTL 検証についても，DFHS の効果が大きく働くと期待できる．さらに，LTL 検証で重要となる公平性の考慮についてDFHS を拡張した．LTL 式としては公平性条件を記述せず，反例の公平性充足を確認する手法により，さらなる改善を図った．拡張したJPF を用いて検証ツール評価用テストプログラムによるDFHS の評価実験を行った．実験の結果，安全性検証，LTL 検証ともに，既存手法よりも多くのケースでDFHS が早期に不具合を発見できることを示し，DFHS による効率化が実現できる可能性が十分に高いことを実証した．本研究による貢献は，(1) 安全性検証について新しいヒューリスティック探索手法を確立し，ヒューリスティック探索適用の幅を広げたこと，(2) 従来不可能であったLTL 検証に対してヒューリスティック探索を実現したこと，(3) 提案手法を実用のツールとして実装したこと，の三点である．電気通信大学201

腎特異的ユビキチンリガーゼRNF183の発現は高浸透圧によりNFAT5を介して誘導される

広島大学(Hiroshima University)博士(医学)Doctor of Philosophy in Medical Sciencedoctora

Changes in winter wheat (Triticum aestivum L.) phenotype in response to breeding for yield and in-furrow fertilizer

Master of ScienceDepartment of AgronomyRomulo P. LollatoThe grain yield of winter wheat (Triticum aestivum L.) increased over time through plant breeding, and preliminary research suggested that yield response to fertilizer differs in modern versus historical genotypes. However, this response is not universal. We hypothesize selection for yield may have unintentionally modified the dynamics of nutrient uptake and partitioning in the plant. Thus, our objectives were to identify the key shifts in crop phenotype, in above-ground biomass and in dynamics of nutrient uptake and partitioning during vegetative and reproductive phases in response to selection for yield and to in-furrow fertilizer. Field experiments were conducted in four Kansas environments in a factorial trial combining eight winter wheat varieties released between 1920 and 2016, and two fertilizer practices (control versus 112 kg ha⁻¹ in-furrow 12-40-0-10-1). Grain yield and grain N-removal increased non-linearly with year of release (YOR), with greater increases between 1966 and 2000. In-furrow fertilizer increased yield in ~300 kg ha⁻¹ with no variety x fertility interactions. Grain protein concentration (GNC) related negatively to yield, and the residuals of this relationship were unaffected by YOR. Yield increase in semi-dwarf varieties were associated with shorter vegetative period and longer grain filling period, and more kernels m⁻² derived from more kernels head⁻¹. Historical varieties were taller, had thinner stems, and allocated more biomass to the stem than semi-dwarf varieties. At grain filling and maturity, shoot biomass was similar among varieties but semi-dwarf varieties allocated more dry matter to the kernels, suggesting that increases in yield derived from greater harvest index (HI) rather than greater biomass. Whole plant nutrient concentration negatively related to whole plant biomass and increased over decades for N, P, and S and decreased for K. In-furrow fertilizer increased the concentration of all nutrients. Grain-N, P, K, and S uptake increased from historical to semi-dwarf varieties; thus, nutrient HI increased with YOR, with greater increases between 1966 and 2000. Nutrient HI decreased with in-furrow fertilizer as the fertilizer increased biomass allocation to the vegetative tissues more than to the grain. Nutrient allocation rate to the head related positively to whole plant uptake rate, and YOR increased the head allocation rate for N, K, and S. There were positive and significant relationships between NHI and the HI of P, K, and S. Whole plant N uptake and P, K, and S uptake were also positively related, with ratios of 9.2, 1.1, and 15.4 for N:P, N:K, and N:S. Direct selection for grain yield modified the dynamics of nutrient uptake and partitioning over time, with semi-dwarf varieties allocating more N, P, K, and S to the grain. The ability of modern varieties to allocate more biomass and nutrients to the grain, coupled to an early maturity and longer grain filling period, increased grain yield and grain N-removal over time. However, increases in yield were greater than those in N-removal, reducing GNC. In-furrow fertilizer increased grain yield, biomass, and grain N, P, K, S uptake; nonetheless, the lack of variety x fertility interaction suggested variety response to fertility was similar

Wheat Development and Yield as Affected by Era of Variety Release and In-Furrow Fertilizer

Limited information exists on the interaction between historical and modern wheat varieties and in-furrow fertilizer. Our objectives were to estimate grain yield and differences in dynamics of biomass accumulation of historical and modern winter wheat varieties as affected by different fertilization practices. Two field trials were established during the 2017–2018 growing season in Kansas. Eight winter wheat varieties released between 1920 and 2016—Kharkof (1920), Scout 66 (1966), Karl 92 (1988), Jagger (1994), Jagalene (2001), Fuller (2006), KanMark (2014) and Larry (2016)—were sown using one of two different fertilizer treatments: either the university recommendation (control with no in-furrow fertilizer due to high testing soil-P levels) or a treatment where 100 lb/a MESZ were applied in-furrow. Grain yield was greater in semi-dwarf varieties relative to tall varieties. In-furrow fertilizer showed greater grain yield in comparison with no fertilizer treatment. Whole plant biomass accumulation at matu­rity did not change over decades. In-furrow fertilizer presented larger biomass accu­mulation than no fertilizer treatment. Harvest index increased from tall to semi-dwarf varieties. More site-years of this study are needed to determine whether there is a need for re-evaluation of current fertility recommendations for semi-dwarf wheat varieties, considering that no interaction between variety and fertility was observed

Wheat Development and Yield as Affected by Era of Variety Release and In-Furrow Fertilizer

Nutrients play a major role in wheat yield determination; however, limited informa­tion exists on the differential responses of historical and modern varieties to in-furrow fertilizer. Our objectives were to estimate grain yield and differences in agronomic traits of historical and modern winter wheat varieties as affected by different fertilization programs. Two field trials were established during the growing season 2016–2017 (i.e., Ashland Bottoms and Belleville, KS). Seven winter wheat varieties released between 1920 and 2016–Kharkof (1920), Scout 66 (1966), Karl 92 (1988), Jagalene (2001), Fuller (2006), KanMark (2014), and Larry (2016)–were sown using one of two different fertilizer practices: either the university recommendation or a treatment where 100 lb/a MESZ were applied in-furrow. At both locations, historical varieties were taller and had thinner stems than modern ones. In-furrow fertilizer increased yield of modern varieties relative to no fertilizer treatment in a sandier soil in Ashland Bottoms, while historical varieties showed neutral to negative yield response. In the silt loam soil near Belleville, there was only a significant variety effect but no fertilizer effect, likely due to a greater cation exchange capacity of the studied soil. More site-years of this study are needed to determine whether there is a need for re-evaluation of current fertility recommendations for modern wheat varieties

Seasonal variation in hemodialysis initiation: A single-center retrospective analysis

The number of new dialysis patients has been increasing worldwide, particularly among elderly individuals. However, information on seasonal variation in hemodialysis initiation in recent decades is lacking, and the seasonal distribution of patients' conditions immediately prior to starting dialysis remains unclear. Having this information could help in developing a modifiable approach to improving pre-dialysis care. We retrospectively investigated the records of 297 patients who initiated hemodialysis at Hiroshima Prefectural Hospital from January 1st, 2009 to December 31st, 2013. Seasonal differences were assessed by χ2 or Kruskal-Wallis tests. Multiple comparison analysis was performed with the Steel test. The overall number of patients starting dialysis was greatest in winter (n = 85, 28.6%), followed by spring (n = 74, 24.9%), summer (n = 70, 23.6%), and autumn (n = 68, 22.9%), though the differences were not significant. However, there was a significant winter peak in dialysis　initiation among patients aged ≥65 years, but not in those aged <65 years. Fluid overload　assessed by clinicians was the most common uremic symptom among all patients, but a　winter peak was only detected in patients aged ≥65 years. The body weight gain ratio　showed a similar trend to fluid overload assessed by clinicians. Pulmonary edema was most　pronounced in winter among patients aged ≥65 years compared with other seasons. The　incidences of infection were modestly increased in summer and winter, but not statistically　significant. Cardiac complications were similar in all seasons. This study demonstrated　the existence of seasonal variation in dialysis initiation, with a winter peak among patients　aged ≥65 years. The winter increment in dialysis initiation was mainly attributable to　increased fluid overload. These findings suggest that elderly individuals should be monitored　particularly closely during the winter