Protocols for spatial allocation of farm types

Farm Management,

Risico inventarisatie van schade door ethyleen bij tussenplanten : effecten van tomaat op tussengeplante komkommer en tomaat

Bij een herfstteelt van trostomaten op goten is het aantrekkelijk om in de winter tomaten of komkommers tussen te planten. Door het grotendeels weg laten zakken van het oude gewas onder de goot en het jonge gewas op de goot te zetten, kan de teeltwisseling met een minder groot gat in de productie verlopen. Omdat trostomaten aan de plant volledig doorkleuren bestaat in principe de kans dat de ethyleen die gevormd wordt door de rijpende vruchten schade kan geven aan het jonge tussengeplante gewas. Bij tomaat is in 2000 op enkele bedrijven trosrui geconstateerd bij het tussengeplante toma tengewas. Hierbij werd gedacht aan mogelijke ethyleenschade. Ethyleen is een gasvormige, planteigen stof die als groeiregulator (hormoon) bij zeer veel verschillende fysiologische processen betrokken is. Het beïnvloedt o.a. bloei, bladgroei en lengtegroei van de spruit (Abeles et al., 1992). Als er externe bronnen zijn van ethyleen dan is er al snel sprake van schade. Symptomen van ethyleenschade zijn o.a. afwijkende kiemplanten, bloemrui, trosrui, afwijkende bladstand, bladval en stagnatie van de vegetatieve groei. Ernstige ethyleenschade uit zich direct in bladvergeling, maar soms treedt er verdekt wat lichte schade op die toch blijkt te leiden tot productiederving. Ethyleen komt in de buitenlucht standaard voor in een concentratie van 1 – 5 ppb (Abeles et al., 1992), maar kan in stedelijke gebieden tot wel 100 keer hoger worden. Ethyleen kan dus als luchtvervuiling een kas binnenkomen, of ophopen ten gevolge van een slecht afgestelde brander (Hanan, 1973, Esmeijer, 1999). Een andere bron van ethyleen is een gewas met doorkleurende vruchten zoals tomaat (Reid, 1988). In het geval van tussenplanten in de winterperiode zou dit problemen kunnen opleveren. In het verleden werd ook wel tussengeplant, maar leidde dit nooit tot problemen, omdat de vruchten los geoogst werden en nooit zo lang doorgekleurd in het gewas aanwezig bleven. Bovendien werd er alleen tussengeplant in de zomermaanden als er relatief veel gelucht werd. Bij tussenplanten in de winter van komkommers bij tomaat gaat het om een situatie waarin de luchtramen vaak gesloten zijn en er weinig licht beschikbaar is. De meeste gewassen zijn in die omstandigheden gevoelig voor schade, en naar verwachting zullen jonge, snel groeiende komkommerplanten op die regel geen uitzondering zijn

APEX-CHAMP+ high-J CO observations of low-mass young stellar objects: II. Distribution and origin of warm molecular gas

The origin and heating mechanisms of warm (50<T<200 K) molecular gas in low-mass young stellar objects (YSOs) are strongly debated. Both passive heating of the inner collapsing envelope by the protostellar luminosity as well as active heating by shocks and by UV associated with the outflows or accretion have been proposed. We aim to characterize the warm gas within protosteller objects, and disentangle contributions from the (inner) envelope, bipolar outflows and the quiescent cloud. High-J CO maps (12CO J=6--5 and 7--6) of the immediate surroundings (up to 10,000 AU) of eight low-mass YSOs are obtained with the CHAMP+ 650/850 GHz array receiver mounted on the APEX telescope. In addition, isotopologue observations of the 13CO J=6--5 transition and [C I] 3P_2-3P_1 line were taken. Strong quiescent narrow-line 12CO 6--5 and 7--6 emission is seen toward all protostars. In the case of HH~46 and Ced 110 IRS 4, the on-source emission originates in material heated by UV photons scattered in the outflow cavity and not just by passive heating in the inner envelope. Warm quiescent gas is also present along the outflows, heated by UV photons from shocks. Shock-heated warm gas is only detected for Class 0 flows and the more massive Class I sources such as HH~46. Outflow temperatures, estimated from the CO 6--5 and 3--2 line wings, are ~100 K, close to model predictions, with the exception of the L~1551 IRS 5 and IRAS 12496-7650, for which temperatures <50 K are found. APEX-CHAMP+ is uniquely suited to directly probe a protostar's feedback on its accreting envelope gas in terms of heating, photodissociation, and outflow dispersal by mapping 1'x1' regions in high-J CO and [C I] lines.Comment: 18 pages, accepted by A&A, A version with the figures in higher quality can be found on my website: http://www.cfa.harvard.edu/~tvankemp

Radio-Frequency Spectroscopy of Ultracold Fermions

Radio-frequency techniques were used to study ultracold fermions. We observed the absence of mean-field "clock" shifts, the dominant source of systematic error in current atomic clocks based on bosonic atoms. This is a direct consequence of fermionic antisymmetry. Resonance shifts proportional to interaction strengths were observed in a three-level system. However, in the strongly interacting regime, these shifts became very small, reflecting the quantum unitarity limit and many-body effects. This insight into an interacting Fermi gas is relevant for the quest to observe superfluidity in this system.Comment: 6 pages, 6 figure

Imaging-Based Surrogate Markers of Epidermal Growth Factor Receptor Mutation in Lung Adenocarcinoma:A Local Perspective

Purpose: To identify computed tomography (CT) features of epidermal growth factor receptor (EGFR) mutation-positive lung adenocarcinoma in Canadian population and whether imaging-based surrogate markers of EGFR mutation in our population were similar to those found in the Asian population. Materials and Methods: Pretreatment CT scans of 223 patients with adenocarcinoma of the lung (112 with EGFR mutation and 111 without mutation) were retrospectively assessed for 20 specific CT features by 2 radiologists, who were blinded to the status of EGFR mutation. Univariate and multivariate logistic regression analyses as well as areas under the receiver operating characteristic curve were performed to discriminate characteristics of EGFR-activating mutation features. Results: Epidermal growth factor receptor mutation-positive adenocarcinomas were more frequently found in female (P <.03), less than 20 pack-year smoking history (P <.001), smaller tumor (P <.01), spiculated margins (P <.05), without centrilobular emphysema (P <.001), and without lymphadenopathy (P <.05), similarly to the Asian population. Multivariate logistic regression analyses of combined clinical and radiological features identified less than 20 pack-year smoking history, smaller tumor diameter, fine or coarse spiculations, noncentral location of the tumor, and lack of centrilobular emphysema and pleural attachment as the strongest independent prognostic factors for the presence of an EGFR mutation. These combined features improved prognostic ability area under the curve to 0.879, compared to 0.788 for clinical features only. Conclusion: Several CT findings may help predict the presence of an activating mutation in EGFR in lung adenocarcinomas in our Canadian population. Combining clinical and radiological features improves prognostic ability to determine the EGFR mutation status compared to clinical features alone

Неустойчивость двухслойных течений в проливах Черного моря

Рассмотрена плоская задача о прогрессивных гравитационных внутренних волнах в горизонтальном двухслойном течении Кельвина-Гельмгольца. Найдено аналитическое решение задачи и условия существования внутренних волн. Для течений с параметрами, типичными для пролива Босфор и Керченского пролива, рассчитаны характеристики бароклинных волн. В пространстве волновых чисел определены диапазоны устойчивости и неустойчивости двухслойных течений с характерными для этих проливов параметрами относительно малых возмущений в форме прогрессивных волн.Розглянуто плоску задачу про прогресивні гравітаційні внутрішні хвилі у горизонтальній двошаровій течії Кельвіна-Гельмгольца. Знайдено аналітичне рішення задачі та умови існування внутрішніх хвиль. Для течій з параметрами, типовими для протоки Босфор і Керченської протоки, розраховані характеристики бароклінних хвиль. У просторі хвильових чисел визначені діапазони стійкості і нестійкості двошарових течій з характерними для цих проток параметрами відносно малих збурень у формі прогресивних хвиль.The plane problem of the progressive internal gravity waves in a horizontal two-layer Kelvin-Helmholtz flow is considered. The analytical solution of the problem and the conditions of existence of internal waves are found. For the flows with the typical parameters for the Bosphorus Strait and the Strait of Kerch, characteristics of baroclinic waves are calculated. The stability and instability regimes of two-layer currents with characteristic parameters of these straits with respect to small wave disturbances are found in the space of wave numbers

Herschel observations of the hydroxyl radical (OH) in young stellar objects

Water in Star-forming regions with Herschel (WISH) is a Herschel Key Program investigating the water chemistry in young stellar objects (YSOs) during protostellar evolution. Hydroxyl (OH) is one of the reactants in the chemical network most closely linked to the formation and destruction of H2O. High-temperature chemistry connects OH and H2O through the OH + H2 H2O + H reactions. Formation of H2O from OH is efficient in the high-temperature regime found in shocks and the innermost part of protostellar envelopes. Moreover, in the presence of UV photons, OH can be produced from the photo-dissociation of H2O. High-resolution spectroscopy of the OH 163.12 micron triplet towards HH 46 and NGC 1333 IRAS 2A was carried out with the Heterodyne Instrument for the Far Infrared (HIFI) on board Herschel. The low- and intermediate-mass YSOs HH 46, TMR 1, IRAS 15398-3359, DK Cha, NGC 7129 FIRS 2, and NGC 1333 IRAS 2A were observed with the Photodetector Array Camera and Spectrometer (PACS) in four transitions of OH and two [OI] lines. The OH transitions at 79, 84, 119, and 163 micron and [OI] emission at 63 and 145 micron were detected with PACS towards the class I low-mass YSOs as well as the intermediate-mass and class I Herbig Ae sources. No OH emission was detected from the class 0 YSO NGC 1333 IRAS 2A, though the 119 micron was detected in absorption. With HIFI, the 163.12 micron was not detected from HH 46 and only tentatively detected from NGC 1333 IRAS 2A. The combination of the PACS and HIFI results for HH 46 constrains the line width (FWHM > 11 km/s) and indicates that the OH emission likely originates from shocked gas. This scenario is supported by trends of the OH flux increasing with the [OI] flux and the bolometric luminosity. Similar OH line ratios for most sources suggest that OH has comparable excitation temperatures despite the different physical properties of the sources.Comment: Accepted for publication in Astronomy and Astrophysics (Herschel special issue