Recent Applications of Unilateral NMR to Objects of Cultural Heritage

Round 1

Reviewer 1 Report

This summary of recent work using single-sided NMR to analyze cultural heritage comes from a team with a strong history in the field. This paper presents several interesting applications via experimental results, and as such reads something as a hybrid of a research article and a review article. It could be helpful for newcomers to the field.

Several aspects of the manuscript should be addressed before publication:

1. The paragraph beginning on line 46 is quite technical in some ways (T2, 2D maps, T2*), and is very vague in others (lines 53-55, technically other nuclei can be detected, though there are some conditions). I recommend revising this paragraph to ensure it reaches the target audience accurately.

2. Equations 1 and 2 are difficult to interpret with the symbols given (A_pi, A_pmin, A_s_pw, A_s_pd, etc.) In addition, I think the defintions of Aspw and Aspd are reversed in lines 138-139.

3. Lines 180-186 are too cumbersome as written for me to evaluate their accuracy.

4. The yellow color in the July 2022 panel of Figure 4 doesn't appear on the legend--is this a high or low humidity? This is a crucial aspect of the paper and must be addressed.

5. The section on canvas paintings is well composed.

6. Lines 541-542 address both longitudinal and transverse relaxation rates in a homogeneous field, though the equation (unlabelled) on line 543 only includes T2 (transverse) relaxation. I don't understand this decision.

7. I do think the manuscript overall is well cited, though only a few groups in the field are represented. Other research should be included, especially as this is something of a review/research article hybrid. (Note: I don't suggest the authors are excessively self-citing, but that the citations could span a larger number of NMR/cultural heritage researchers.)

Moderate copyediting would improve the readability of the manuscript. Paragraph 1 on page 5 is particularly cumbersome.

Author Response

Reviewer 1

1. The paragraph beginning on line 46 is quite technical in some ways (T2, 2D maps, T2*), and is very vague in others (lines 53-55, technically other nuclei can be detected, though there are some conditions). I recommend revising this paragraph to ensure it reaches the target audience accurately.

This paragraph was revised.

2. Equations 1 and 2 are difficult to interpret with the symbols given (A_pi, A_pmin, A_s_pw, A_s_pd, etc.) In addition, I think the defintions of Aspw and Aspd are reversed in lines 138-139.

We simplified  the equation 1, now become equation 2 as:

We also corrected the definitions of Asw and Asd, that appear reversed in the text.

3. Lines 180-186 are too cumbersome as written for me to evaluate their accuracy.

We reformulated the sentence.

4. The yellow color in the July 2022 panel of Figure 4 doesn't appear on the legend--is this a high or low humidity? This is a crucial aspect of the paper and must be addressed.

The yellow color corresponds to a low humidity value. We have changed the legend of figure 4 expanding the gradient of the colors.

6. Lines 541-542 address both longitudinal and transverse relaxation rates in a homogeneous field, though the equation (unlabelled) on line 543 only includes T2 (transverse) relaxation. I don't understand this decision.

As the effect of inhomogeneity of the magnetic field affects the transverse relaxation times, we revised the line to refer to the equation labeled T2.

7. I do think the manuscript overall is well cited, though only a few groups in the field are represented. Other research should be included, especially as this is something of a review/research article hybrid. (Note: I don't suggest the authors are excessively self-citing, but that the citations could span a larger number of NMR/cultural heritage researchers.)

We added other references of  works NMR/cultural heritage from other  researcher teams.

Author Response File: Author Response.pdf

Reviewer 2 Report

Heritage-2932780-peer-review-v1: Portable Unilateral NMR Technique for Cultural Heritage Applications

The manuscript reports a set of different studies of objects valuable to cultural heritage with unilateral NMR. Overall, the reported work is worth publishing, but the manuscript needs to be revised extensively. 

-       Title: The title is more fitting to a review than to a summary of the authors’ recent work. The authors may want to consider a title like the following: Recent applications of unilateral NMR to objects of cultural heritage. 

-       Introduction: The authors state, that “research has sought to address these issues by developing progressively advanced technologies that are mostly portable and non-invasive”. Here one or two reference to a review, a book or the MoLab activity would be helpful. Also, the authors may want to reference some more recent work or reviews of others reporting studies of cultural heritage with unilateral NMR in the introduction.

-       While certain language deficiencies can be tolerated as long as the text can be understood, this text contains many, which could have easily been noticed with due diligence at the proof-reading stage. It is puzzling that both authors state that they have reviewed and edited the text but missed errors like “reffered”, “single sides NMR”, “¹H, knows as the proton”, “capillary forces can to move water”, etc. I leave it to the editor to suggest ways how to improve the English writing. 

-       Fast-mas NMR à fast MAS NMR

-       In this statement the basic science is wrong: “T₂* (read as T₂ star) will be the sum of the “natural” or ”true” transverse time T₂ and the inhomogeneity contribution T_2inhom, making T₂* ≤ T₂ relaxation time”. à The relaxation rates are additive and not the relaxation times. 

-       The literature citations are inconsistent, e.g. [^vi-^vii], [6], [xxxi-xxxii]. The different notations suggest that some text sections have been copied from other sources and pasted into this manuscript. References [6], [5,10] and [19,21] are not listed under References.

-       Figure 1 shows two sensor configurations: “sensible volume” should read “sensitive volume”. What is the field characteristic of the Bruker sensor (a) compared to the uniform gradient sensor (b)? The manufacturer of sensor (b) is specified as RWTH Aachen University in the figure legend. But further down it is specified as Magritek. Please explain and/or consolidate.

-       The text to Fig. 1b states that unilateral sensors can scan depths form 0 up to 1.0 cm: This may be applicable to the sensor employed in the studies reported in the manuscript. But one can buy sensors with depth ranges from 0 to 2 mm all the way up to 0 – 25 mm. Please clarify if you are referring to your particular sensor or if you want to make a general statement.

-       The authors state that “electrical conductivity may be affected by the presence of salts”. They certainly are! Pure water is an insulator. This is why electrical measurements of moisture content are indirect as opposed to ¹H NMR.

-       The text explaining equation (1) refers to vault and apse without explanation why these terms are being used. Only further down it becomes clear that this terminology has been chosen in the context of a particular study. Please reorganize the text to avoid confusing the reader. Also, it may be helpful to explain if you are specifying volumetric or gravimetric moisture content. Furthermore, it is important to mention at what depth the moisture content has been measured, as typically it varies with depth into the wall, depending on the moisture flux.

-       “In the literature numerous experiments on water-saturated rocks have shown that relaxation-time distributions are similar to pore-size distributions obtained by other techniques such as Mercury Intrusion Porosimetry (MIP).” à Please provide a reference to a book or a review. 

-       Organization of the manuscript: Section 2 reports three case studies in subsections 2.1 to 2.6. It would be less confusing to number the subsections 2.1, 2.2, and 2.3 rather than giving the experimental details of each study a separate subsection number with equal priority. The experimental details could be given in separate subsections 3.1, 3.2, and 3.3.

It is advised that before submitting the revision, a third person well familiar with the English language proofreads your work. 

While certain language deficiencies can be tolerated as long as the text can be understood, this text contains many, which could have easily been noticed with due diligence at the proof-reading stage. It is puzzling that both authors state that they have reviewed and edited the text but missed errors like “reffered”, “single sides NMR”, “¹H, knows as the proton”, “capillary forces can to move water”, etc. I leave it to the editor to suggest ways how to improve the English writing. It is advised that before submitting the revision, a third person well familiar with the English language proofreads your work. 

Author Response

Reviewer 2

-       Title: The title is more fitting to a review than to a summary of the authors’ recent work. The authors may want to consider a title like the following: Recent applications of unilateral NMR to objects of cultural heritage.

 As suggested by the reviewer we accepted to change the title with “ Recent applications of unilateral NMR to objects of cultural heritage”

-       Introduction: The authors state, that “research has sought to address these issues by developing progressively advanced technologies that are mostly portable and non-invasive”. Here one or two reference to a review, a book or the MoLab activity would be helpful. Also, the authors may want to reference some more recent work or reviews of others reporting studies of cultural heritage with unilateral NMR in the introduction.

As suggested by the reviewer we inserted two references on the development of technologies portable for studying Cultural heritage. Moreover we added in the introduction more recent publications on studies of Cultural Heritage by Unilateral NMR.

-       While certain language deficiencies can be tolerated as long as the text can be understood, this text contains many, which could have easily been noticed with due diligence at the proof-reading stage. It is puzzling that both authors state that they have reviewed and edited the text but missed errors like “reffered”, “single sides NMR”, “1H, knows as the proton”, “capillary forces can to move water”, etc. I leave it to the editor to suggest ways how to improve the English writing.

We revised the English of the article and the language deficiencies were corrected.

-       Fast-mas NMR à fast MAS NMR

Done

-       In this statement the basic science is wrong: “T2* (read as T2 star) will be the sum of the “natural” or ”true” transverse time T2 and the inhomogeneity contribution T2inhom, making T2* ≤ T2 relaxation time”. à The relaxation rates are additive and not the relaxation times.

We revised and corrected this sentence.

-       The literature citations are inconsistent, e.g. [vi-vii], [6], [xxxi-xxxii]. The different notations suggest that some text sections have been copied from other sources and pasted into this manuscript. References [6], [5,10] and [19,21] are not listed under References.

We checked all references in revised file.

-       Figure 1 shows two sensor configurations: “sensible volume” should read “sensitive volume”.

Done

What is the field characteristic of the Bruker sensor (a) compared to the uniform gradient sensor (b)?

In the Bruker sensor, figure 1a, the magnetic field is generated using two anti-parallel permanent magnets mounted on an iron yoke with the radio frequency (RF) coil positioned in the gap. By tuning the rf frequency, the depth or the distance to the sensor surface where the sensitive volume is generated can be shifted. Optimizing the magnet and the rf coil geometries, a flat sensitive volume can be generated at  variable distance from the sensor surface. In the uniform gradient  sensor, figure 1b,  a new magnet geometry, consisting of four permanent magnet blocks positioned on an iron yoke,  is used to generate a highly flat sensitive volume. The important advantage of this magnet geometry relies on  the fact that the static field is parallel to its surface, allowing its combination with simple and efficient surface RF coils. These last devices generate an inhomogeneous magnetic field with a uniform gradient to resolve the near surface structure of arbitrarily large samples. To improve gradient uniformity, the device works at a fixed depth from the sensor, where high depth resolution can be achieved. The position of the excited slice inside the sample can be varied by displacing the sensor using a high-precision lift that repositions the magnet with respect to the sample.

The manufacturer of sensor (b) is specified as RWTH Aachen University in the figure legend. But further down it is specified as Magritek. Please explain and/or consolidate.

The sensor showed in figure 1b was one of the first sensors developed in 2008 by the spin-off of the RWTH Aachen University, today known as the Company Magritek. We modified in the text changed RWTH Aachen University with Magritek.

-       The text to Fig. 1b states that unilateral sensors can scan depths form 0 up to 1.0 cm: This may be applicable to the sensor employed in the studies reported in the manuscript. But one can buy sensors with depth ranges from 0 to 2 mm all the way up to 0 – 25 mm. Please clarify if you are referring to your particular sensor or if you want to make a general statement.

The sensor showed in figure 1b is a commercially available sensor known as NMR MOUSE PM10.  It can scan depths form 0 up to 1.0 cm. The only difference is that the sensor used in this study is interfaced with a Bruker electronic unit  instead of Magritek electronic unit. Commercially there are sensors NMR MOUSE PM2,  scan depths form 0 up to 2mm, NMR MOUSE PM5, scan depths form 0 up to 5mm,  NMR MOUSE PM25, scan depths form 0 up to 25mm.

-       The authors state that “electrical conductivity may be affected by the presence of salts”. They certainly are! Pure water is an insulator. This is why electrical measurements of moisture content are indirect as opposed to 1H NMR.

We apologize to the reviewer but we do not understand if any changes are required.

-       The text explaining equation (1) refers to vault and apse without explanation why these terms are being used. Only further down it becomes clear that this terminology has been chosen in the context of a particular study. Please reorganize the text to avoid confusing the reader. Also, it may be helpful to explain if you are specifying volumetric or gravimetric moisture content. Furthermore, it is important to mention at what depth the moisture content has been measured, as typically it varies with depth into the wall, depending on the moisture flux.

The text was reorganized, sentences have been corrected and the measurement depth has been clarified.

-       “In the literature numerous experiments on water-saturated rocks have shown that relaxation-time distributions are similar to pore-size distributions obtained by other techniques such as Mercury Intrusion Porosimetry (MIP).” à Please provide a reference to a book or a review.

We added two references.

-       Organization of the manuscript: Section 2 reports three case studies in subsections 2.1 to 2.6. It would be less confusing to number the subsections 2.1, 2.2, and 2.3 rather than giving the experimental details of each study a separate subsection number with equal priority. The experimental details could be given in separate subsections 3.1, 3.2, and 3.3.

We agreed to the reviewer’s suggestion and moved the experimental section to the bottom before the conclusions.

It is advised that before submitting the revision, a third person well familiar with the English language proofreads your work.

Done

Author Response File: Author Response.pdf

Round 2

Reviewer 2 Report

The authors satisfactorily revised the manuscript

Author Response

Prof. Silvano Mignardi

Editor of Special Issue 

“Non-invasive Technologies Applied in Cultural Heritage” Heritage Journal

Mr. Vladan Travičić

Section Managing Editor

Dear Editors,

Enclosed you will find a revised copy of the manuscript n 2932780 entitled “Recent applications of unilateral NMR to objects of cultural heritage” by Di Tullio Valeria and Proietti Noemi.

We still wish to thank reviewers for the suggestions aimed to improve the paper.

In this last version of the manuscript, we delete references 14, 20 and 30 as suggested by Academic Editor to achieve the self-citation rate accepted by the journal.

                               With the Best Regards

                                Dr. Noemi Proietti

Author Response File: Author Response.pdf